On 2021-Jan-10, Justin Pryzby wrote:

> On Fri, Jan 08, 2021 at 04:14:33PM -0300, Alvaro Herrera wrote:
> > > > I ended up with apparently broken constraint when running multiple 
> > > > loops around
> > > > a concurrent detach / attach:
> > > > 
> > > > while psql -h /tmp postgres -c "ALTER TABLE p ATTACH PARTITION p1 FOR 
> > > > VALUES FROM (1)TO(2)" -c "ALTER TABLE p DETACH PARTITION p1 
> > > > CONCURRENTLY"; do :; done&
> > > > while psql -h /tmp postgres -c "ALTER TABLE p ATTACH PARTITION p1 FOR 
> > > > VALUES FROM (1)TO(2)" -c "ALTER TABLE p DETACH PARTITION p1 
> > > > CONCURRENTLY"; do :; done&
> > > > 
> > > >     "p1_check" CHECK (true)
> > > >     "p1_i_check" CHECK (i IS NOT NULL AND i >= 1 AND i < 2)
> > > 
> > > Not good.
> > 
> > Haven't had time to investigate this problem yet.
> 
> I guess it's because you commited the txn and released lock in the middle of
> the command.

Hmm, but if we take this approach, then we're still vulnerable to the
problem that somebody can do DETACH CONCURRENTLY and cancel the wait (or
crash the server), then mess up the state before doing DETACH FINALIZE:
when they cancel the wait, the lock will be released.

I think the right fix is to disallow any action on a partition which is
pending detach other than DETACH FINALIZE.  (Didn't do that here.)

Here's a rebase to current sources; there are no changes from v5.

-- 
Álvaro Herrera       Valdivia, Chile
"No hay ausente sin culpa ni presente sin disculpa" (Prov. francés)
>From d042b99ad3368ba0b658ac9260450ed8e39accea Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvhe...@alvh.no-ip.org>
Date: Mon, 13 Jul 2020 20:15:30 -0400
Subject: [PATCH v6 1/2] Let ALTER TABLE exec routines deal with the relation

This means that ATExecCmd relies on AlteredRelationInfo->rel instead of
keeping the relation as a local variable; this is useful if the
subcommand needs to modify the relation internally.  For example, a
subcommand that internally commits its transaction needs this.
---
 src/backend/commands/tablecmds.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b2457a6924..b990063d38 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -156,6 +156,8 @@ typedef struct AlteredTableInfo
 	Oid			relid;			/* Relation to work on */
 	char		relkind;		/* Its relkind */
 	TupleDesc	oldDesc;		/* Pre-modification tuple descriptor */
+	/* Transiently set during Phase 2, normally set to NULL */
+	Relation	rel;
 	/* Information saved by Phase 1 for Phase 2: */
 	List	   *subcmds[AT_NUM_PASSES]; /* Lists of AlterTableCmd */
 	/* Information saved by Phases 1/2 for Phase 3: */
@@ -353,7 +355,7 @@ static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 					  AlterTableUtilityContext *context);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
 							  AlterTableUtilityContext *context);
-static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
+static void ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 					  AlterTableCmd *cmd, LOCKMODE lockmode, int cur_pass,
 					  AlterTableUtilityContext *context);
 static AlterTableCmd *ATParseTransformCmd(List **wqueue, AlteredTableInfo *tab,
@@ -4513,7 +4515,6 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
 		{
 			AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
 			List	   *subcmds = tab->subcmds[pass];
-			Relation	rel;
 			ListCell   *lcmd;
 
 			if (subcmds == NIL)
@@ -4522,10 +4523,10 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
 			/*
 			 * Appropriate lock was obtained by phase 1, needn't get it again
 			 */
-			rel = relation_open(tab->relid, NoLock);
+			tab->rel = relation_open(tab->relid, NoLock);
 
 			foreach(lcmd, subcmds)
-				ATExecCmd(wqueue, tab, rel,
+				ATExecCmd(wqueue, tab,
 						  castNode(AlterTableCmd, lfirst(lcmd)),
 						  lockmode, pass, context);
 
@@ -4537,7 +4538,11 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
 			if (pass == AT_PASS_ALTER_TYPE)
 				ATPostAlterTypeCleanup(wqueue, tab, lockmode);
 
-			relation_close(rel, NoLock);
+			if (tab->rel)
+			{
+				relation_close(tab->rel, NoLock);
+				tab->rel = NULL;
+			}
 		}
 	}
 
@@ -4563,11 +4568,12 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
  * ATExecCmd: dispatch a subcommand to appropriate execution routine
  */
 static void
-ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
+ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 		  AlterTableCmd *cmd, LOCKMODE lockmode, int cur_pass,
 		  AlterTableUtilityContext *context)
 {
 	ObjectAddress address = InvalidObjectAddress;
+	Relation	rel = tab->rel;
 
 	switch (cmd->subtype)
 	{
@@ -5670,6 +5676,7 @@ ATGetQueueEntry(List **wqueue, Relation rel)
 	 */
 	tab = (AlteredTableInfo *) palloc0(sizeof(AlteredTableInfo));
 	tab->relid = relid;
+	tab->rel = NULL;			/* set later */
 	tab->relkind = rel->rd_rel->relkind;
 	tab->oldDesc = CreateTupleDescCopyConstr(RelationGetDescr(rel));
 	tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
-- 
2.20.1

>From 7cc4cc8aa0f7897a51dac3bcc3fc2b6f13b0c3f9 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvhe...@alvh.no-ip.org>
Date: Mon, 3 Aug 2020 19:21:09 -0400
Subject: [PATCH v6 2/2] ALTER TABLE ... DETACH CONCURRENTLY

---
 doc/src/sgml/catalogs.sgml                    |  10 +
 doc/src/sgml/ref/alter_table.sgml             |  25 +-
 src/backend/catalog/heap.c                    |  13 +-
 src/backend/catalog/index.c                   |   4 +-
 src/backend/catalog/partition.c               |  28 +-
 src/backend/catalog/pg_inherits.c             |  51 +-
 src/backend/commands/indexcmds.c              |   7 +-
 src/backend/commands/tablecmds.c              | 568 ++++++++++++++----
 src/backend/commands/trigger.c                |   5 +-
 src/backend/executor/execPartition.c          |  29 +-
 src/backend/nodes/copyfuncs.c                 |   1 +
 src/backend/nodes/equalfuncs.c                |   1 +
 src/backend/optimizer/util/plancat.c          |  11 +-
 src/backend/parser/gram.y                     |  23 +-
 src/backend/partitioning/partbounds.c         |   6 +-
 src/backend/partitioning/partdesc.c           |  21 +-
 src/backend/tcop/utility.c                    |  19 +
 src/backend/utils/cache/partcache.c           |  15 +-
 src/bin/psql/describe.c                       |  40 +-
 src/include/catalog/pg_inherits.h             |   7 +-
 src/include/nodes/parsenodes.h                |   2 +
 src/include/parser/kwlist.h                   |   1 +
 src/include/partitioning/partdesc.h           |   5 +-
 src/include/utils/snapmgr.h                   |   1 +
 .../detach-partition-concurrently-1.out       | 301 ++++++++++
 .../detach-partition-concurrently-2.out       |  66 ++
 src/test/isolation/isolation_schedule         |   2 +
 .../detach-partition-concurrently-1.spec      |  90 +++
 .../detach-partition-concurrently-2.spec      |  41 ++
 src/test/modules/delay_execution/Makefile     |   3 +-
 .../expected/partition-removal-1.out          |  79 +++
 .../specs/partition-removal-1.spec            |  45 ++
 32 files changed, 1347 insertions(+), 173 deletions(-)
 create mode 100644 src/test/isolation/expected/detach-partition-concurrently-1.out
 create mode 100644 src/test/isolation/expected/detach-partition-concurrently-2.out
 create mode 100644 src/test/isolation/specs/detach-partition-concurrently-1.spec
 create mode 100644 src/test/isolation/specs/detach-partition-concurrently-2.spec
 create mode 100644 src/test/modules/delay_execution/expected/partition-removal-1.out
 create mode 100644 src/test/modules/delay_execution/specs/partition-removal-1.spec

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index db29905e91..95293788d4 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -4485,6 +4485,16 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
        when using declarative partitioning.
       </para></entry>
      </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>inhdetached</structfield> <type>bool</type>
+      </para>
+      <para>
+       Set to true for a partition that is in the process of being detached;
+       false otherwise.
+      </para></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index c25ef5abd6..09673dcf1c 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -36,7 +36,9 @@ ALTER TABLE ALL IN TABLESPACE <replaceable class="parameter">name</replaceable>
 ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ATTACH PARTITION <replaceable class="parameter">partition_name</replaceable> { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT }
 ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
-    DETACH PARTITION <replaceable class="parameter">partition_name</replaceable>
+    DETACH PARTITION <replaceable class="parameter">partition_name</replaceable> [ CONCURRENTLY ]
+ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+    DETACH PARTITION <replaceable class="parameter">partition_name</replaceable> FINALIZE
 
 <phrase>where <replaceable class="parameter">action</replaceable> is one of:</phrase>
 
@@ -938,7 +940,8 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
    </varlistentry>
 
    <varlistentry>
-    <term><literal>DETACH PARTITION</literal> <replaceable class="parameter">partition_name</replaceable></term>
+    <term><literal>DETACH PARTITION</literal> <replaceable class="parameter">partition_name</replaceable> [ { CONCURRENTLY | FINALIZE } ]</term>
+
     <listitem>
      <para>
       This form detaches the specified partition of the target table.  The detached
@@ -947,6 +950,24 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       attached to the target table's indexes are detached.  Any triggers that
       were created as clones of those in the target table are removed.
      </para>
+     <para>
+      If <literal>CONCURRENTLY</literal> is specified, this process runs in two
+      transactions in order to avoid blocking other sessions that might be accessing
+      the partitioned table.  During the first transaction, a
+      <literal>SHARE UPDATE EXCLUSIVE</literal> lock is taken on both parent table and
+      partition, and its partition is marked detached; at that point, the transaction
+      is committed and all transactions using the partitioned table are waited for.
+      Once all those transactions are gone, the second stage acquires
+      <literal>ACCESS EXCLUSIVE</literal> on the partition, and the detach process
+      completes.
+      <literal>CONCURRENTLY</literal> is not allowed if the
+      partitioned table contains a default partition.
+     </para>
+     <para>
+      If <literal>FINALIZE</literal> is specified, a previous
+      <literal>DETACH CONCURRENTLY</literal> invocation that was cancelled or
+      interrupted is completed.
+     </para>
     </listitem>
    </varlistentry>
 
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 9abc4a1f55..1a05f2a2fe 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -2555,10 +2555,12 @@ StoreConstraints(Relation rel, List *cooked_constraints, bool is_internal)
  * Returns a list of CookedConstraint nodes that shows the cooked form of
  * the default and constraint expressions added to the relation.
  *
- * NB: caller should have opened rel with AccessExclusiveLock, and should
- * hold that lock till end of transaction.  Also, we assume the caller has
- * done a CommandCounterIncrement if necessary to make the relation's catalog
- * tuples visible.
+ * NB: caller should have opened rel with some self-conflicting lock mode,
+ * and should hold that lock till end of transaction; for normal cases that'll
+ * be AccessExclusiveLock, but if caller knows that the constraint is already
+ * enforced by some other means, it can be ShareUpdateExclusiveLock.  Also, we
+ * assume the caller has done a CommandCounterIncrement if necessary to make
+ * the relation's catalog tuples visible.
  */
 List *
 AddRelationNewConstraints(Relation rel,
@@ -3827,7 +3829,8 @@ StorePartitionBound(Relation rel, Relation parent, PartitionBoundSpec *bound)
 	 * relcache entry for that partition every time a partition is added or
 	 * removed.
 	 */
-	defaultPartOid = get_default_oid_from_partdesc(RelationGetPartitionDesc(parent));
+	defaultPartOid =
+		get_default_oid_from_partdesc(RelationGetPartitionDesc(parent, false));
 	if (OidIsValid(defaultPartOid))
 		CacheInvalidateRelcacheByRelid(defaultPartOid);
 
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 4ef61b5efd..28f04a0700 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -1836,7 +1836,7 @@ index_concurrently_swap(Oid newIndexId, Oid oldIndexId, const char *oldName)
 		List	   *ancestors = get_partition_ancestors(oldIndexId);
 		Oid			parentIndexRelid = linitial_oid(ancestors);
 
-		DeleteInheritsTuple(oldIndexId, parentIndexRelid);
+		DeleteInheritsTuple(oldIndexId, parentIndexRelid, false, NULL);
 		StoreSingleInheritance(newIndexId, parentIndexRelid, 1);
 
 		list_free(ancestors);
@@ -2486,7 +2486,7 @@ index_drop(Oid indexId, bool concurrent, bool concurrent_lock_mode)
 	/*
 	 * fix INHERITS relation
 	 */
-	DeleteInheritsTuple(indexId, InvalidOid);
+	DeleteInheritsTuple(indexId, InvalidOid, false, NULL);
 
 	/*
 	 * We are presently too lazy to attempt to compute the new correct value
diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index af7754d6ab..4327a0b150 100644
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -32,7 +32,7 @@
 #include "utils/rel.h"
 #include "utils/syscache.h"
 
-static Oid	get_partition_parent_worker(Relation inhRel, Oid relid);
+static Oid	get_partition_parent_worker(Relation inhRel, Oid relid, bool *detached);
 static void get_partition_ancestors_worker(Relation inhRel, Oid relid,
 										   List **ancestors);
 
@@ -42,6 +42,9 @@ static void get_partition_ancestors_worker(Relation inhRel, Oid relid,
  *
  * Returns inheritance parent of a partition by scanning pg_inherits
  *
+ * If the partition is in the process of being detached, InvalidOid is
+ * returned and no error is thrown.
+ *
  * Note: Because this function assumes that the relation whose OID is passed
  * as an argument will have precisely one parent, it should only be called
  * when it is known that the relation is a partition.
@@ -51,12 +54,15 @@ get_partition_parent(Oid relid)
 {
 	Relation	catalogRelation;
 	Oid			result;
+	bool		detached;
 
 	catalogRelation = table_open(InheritsRelationId, AccessShareLock);
 
-	result = get_partition_parent_worker(catalogRelation, relid);
+	result = get_partition_parent_worker(catalogRelation, relid, &detached);
 
-	if (!OidIsValid(result))
+	if (detached)
+		result = InvalidOid;
+	else if (!OidIsValid(result))
 		elog(ERROR, "could not find tuple for parent of relation %u", relid);
 
 	table_close(catalogRelation, AccessShareLock);
@@ -70,13 +76,15 @@ get_partition_parent(Oid relid)
  *		given relation
  */
 static Oid
-get_partition_parent_worker(Relation inhRel, Oid relid)
+get_partition_parent_worker(Relation inhRel, Oid relid, bool *detached)
 {
 	SysScanDesc scan;
 	ScanKeyData key[2];
 	Oid			result = InvalidOid;
 	HeapTuple	tuple;
 
+	*detached = false;
+
 	ScanKeyInit(&key[0],
 				Anum_pg_inherits_inhrelid,
 				BTEqualStrategyNumber, F_OIDEQ,
@@ -93,7 +101,14 @@ get_partition_parent_worker(Relation inhRel, Oid relid)
 	{
 		Form_pg_inherits form = (Form_pg_inherits) GETSTRUCT(tuple);
 
-		result = form->inhparent;
+		/* A partition being detached has no parent */
+		if (form->inhdetached)
+		{
+			*detached = true;
+			result = InvalidOid;
+		}
+		else
+			result = form->inhparent;
 	}
 
 	systable_endscan(scan);
@@ -134,9 +149,10 @@ static void
 get_partition_ancestors_worker(Relation inhRel, Oid relid, List **ancestors)
 {
 	Oid			parentOid;
+	bool		detached;
 
 	/* Recursion ends at the topmost level, ie., when there's no parent */
-	parentOid = get_partition_parent_worker(inhRel, relid);
+	parentOid = get_partition_parent_worker(inhRel, relid, &detached);
 	if (parentOid == InvalidOid)
 		return;
 
diff --git a/src/backend/catalog/pg_inherits.c b/src/backend/catalog/pg_inherits.c
index 5ab7902827..3fd0880ca0 100644
--- a/src/backend/catalog/pg_inherits.c
+++ b/src/backend/catalog/pg_inherits.c
@@ -52,7 +52,8 @@ typedef struct SeenRelsEntry
  * against possible DROPs of child relations.
  */
 List *
-find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
+find_inheritance_children(Oid parentrelId, bool include_detached,
+						  LOCKMODE lockmode)
 {
 	List	   *list = NIL;
 	Relation	relation;
@@ -91,7 +92,13 @@ find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
 
 	while ((inheritsTuple = systable_getnext(scan)) != NULL)
 	{
+		/* skip detached at caller's request */
+		if (((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetached &&
+			!include_detached)
+			continue;
+
 		inhrelid = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhrelid;
+
 		if (numoids >= maxoids)
 		{
 			maxoids *= 2;
@@ -160,6 +167,9 @@ find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
  * given rel; caller should already have locked it).  If lockmode is NoLock
  * then no locks are acquired, but caller must beware of race conditions
  * against possible DROPs of child relations.
+ *
+ * NB - No current callers of this routine are interested in children being
+ * concurrently detached, so there's no provision to include them.
  */
 List *
 find_all_inheritors(Oid parentrelId, LOCKMODE lockmode, List **numparents)
@@ -199,7 +209,8 @@ find_all_inheritors(Oid parentrelId, LOCKMODE lockmode, List **numparents)
 		ListCell   *lc;
 
 		/* Get the direct children of this rel */
-		currentchildren = find_inheritance_children(currentrel, lockmode);
+		currentchildren = find_inheritance_children(currentrel, false,
+													lockmode);
 
 		/*
 		 * Add to the queue only those children not already seen. This avoids
@@ -430,6 +441,7 @@ StoreSingleInheritance(Oid relationId, Oid parentOid, int32 seqNumber)
 	values[Anum_pg_inherits_inhrelid - 1] = ObjectIdGetDatum(relationId);
 	values[Anum_pg_inherits_inhparent - 1] = ObjectIdGetDatum(parentOid);
 	values[Anum_pg_inherits_inhseqno - 1] = Int32GetDatum(seqNumber);
+	values[Anum_pg_inherits_inhdetached - 1] = BoolGetDatum(false);
 
 	memset(nulls, 0, sizeof(nulls));
 
@@ -449,10 +461,21 @@ StoreSingleInheritance(Oid relationId, Oid parentOid, int32 seqNumber)
  * as InvalidOid, in which case all tuples matching inhrelid are deleted;
  * otherwise only delete tuples with the specified inhparent.
  *
+ * 'detached' is the expected state of the inhdetached flag.  If the catalog
+ * row does not match that state, an error is raised.  When used on
+ * partitions, the partition name must be passed, for possible error messages.
+ *
+ * If allow_detached is passed false, then an error is raised if the child is
+ * already marked detached.  A name must be supplied in that case, for the
+ * error message.  This should only be used with table partitions.
+ * XXX the name bit is pretty weird and problematic for non-partition cases;
+ * what if the flag check fails?
+ *
  * Returns whether at least one row was deleted.
  */
 bool
-DeleteInheritsTuple(Oid inhrelid, Oid inhparent)
+DeleteInheritsTuple(Oid inhrelid, Oid inhparent, bool detached,
+					const char *childname)
 {
 	bool		found = false;
 	Relation	catalogRelation;
@@ -479,6 +502,28 @@ DeleteInheritsTuple(Oid inhrelid, Oid inhparent)
 		parent = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhparent;
 		if (!OidIsValid(inhparent) || parent == inhparent)
 		{
+			bool	inhdetached;
+
+			inhdetached = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetached;
+
+			/*
+			 * Raise error depending on state.  This should only happen for
+			 * partitions, but we have no way to cross-check.
+			 */
+			if (inhdetached && !detached)
+				ereport(ERROR,
+						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+						 errmsg("cannot detach partition \"%s\"",
+								childname),
+						 errdetail("The partition is being detached concurrently or has an unfinished detach."),
+						 errhint("Use ALTER TABLE ... DETACH PARTITION ... FINALIZE to complete the pending detach operation")));
+			if (!inhdetached && detached)
+				ereport(ERROR,
+						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+						 errmsg("cannot complete detaching partition \"%s\"",
+								childname),
+						 errdetail("There's no pending concurrent detach.")));
+
 			CatalogTupleDelete(catalogRelation, &inheritsTuple->t_self);
 			found = true;
 		}
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 8bc652ecd3..82670bac21 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -410,7 +410,7 @@ CompareOpclassOptions(Datum *opts1, Datum *opts2, int natts)
  * GetCurrentVirtualXIDs.  If, during any iteration, a particular vxid
  * doesn't show up in the output, we know we can forget about it.
  */
-static void
+void
 WaitForOlderSnapshots(TransactionId limitXmin, bool progress)
 {
 	int			n_old_snapshots;
@@ -1123,7 +1123,7 @@ DefineIndex(Oid relationId,
 	 */
 	if (partitioned && stmt->relation && !stmt->relation->inh)
 	{
-		PartitionDesc pd = RelationGetPartitionDesc(rel);
+		PartitionDesc pd = RelationGetPartitionDesc(rel, false);
 
 		if (pd->nparts != 0)
 			flags |= INDEX_CREATE_INVALID;
@@ -1180,7 +1180,7 @@ DefineIndex(Oid relationId,
 		 *
 		 * If we're called internally (no stmt->relation), recurse always.
 		 */
-		partdesc = RelationGetPartitionDesc(rel);
+		partdesc = RelationGetPartitionDesc(rel, false);
 		if ((!stmt->relation || stmt->relation->inh) && partdesc->nparts > 0)
 		{
 			int			nparts = partdesc->nparts;
@@ -4073,6 +4073,7 @@ IndexSetParentIndex(Relation partitionIdx, Oid parentOid)
 			values[Anum_pg_inherits_inhparent - 1] =
 				ObjectIdGetDatum(parentOid);
 			values[Anum_pg_inherits_inhseqno - 1] = Int32GetDatum(1);
+			values[Anum_pg_inherits_inhdetached - 1] = BoolGetDatum(false);
 			memset(isnull, false, sizeof(isnull));
 
 			tuple = heap_form_tuple(RelationGetDescr(pg_inherits),
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b990063d38..91ef4760f6 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -542,7 +542,8 @@ static PartitionSpec *transformPartitionSpec(Relation rel, PartitionSpec *partsp
 static void ComputePartitionAttrs(ParseState *pstate, Relation rel, List *partParams, AttrNumber *partattrs,
 								  List **partexprs, Oid *partopclass, Oid *partcollation, char strategy);
 static void CreateInheritance(Relation child_rel, Relation parent_rel);
-static void RemoveInheritance(Relation child_rel, Relation parent_rel);
+static void RemoveInheritance(Relation child_rel, Relation parent_rel,
+							  bool allow_detached);
 static ObjectAddress ATExecAttachPartition(List **wqueue, Relation rel,
 										   PartitionCmd *cmd,
 										   AlterTableUtilityContext *context);
@@ -551,8 +552,14 @@ static void QueuePartitionConstraintValidation(List **wqueue, Relation scanrel,
 											   List *partConstraint,
 											   bool validate_default);
 static void CloneRowTriggersToPartition(Relation parent, Relation partition);
+static void DetachAddConstraintIfNeeded(List **wqueue, Relation partRel);
 static void DropClonedTriggersFromPartition(Oid partitionId);
-static ObjectAddress ATExecDetachPartition(Relation rel, RangeVar *name);
+static ObjectAddress ATExecDetachPartition(List **wqueue, AlteredTableInfo *tab,
+										   Relation rel, RangeVar *name,
+										   bool concurrent);
+static void DetachPartitionFinalize(Relation rel, Relation partRel,
+									bool concurrent, Oid defaultPartOid, bool wait);
+static ObjectAddress ATExecDetachPartitionFinalize(Relation rel, RangeVar *name);
 static ObjectAddress ATExecAttachPartitionIdx(List **wqueue, Relation rel,
 											  RangeVar *name);
 static void validatePartitionedIndex(Relation partedIdx, Relation partedTbl);
@@ -987,7 +994,8 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 		 * lock the partition so as to avoid a deadlock.
 		 */
 		defaultPartOid =
-			get_default_oid_from_partdesc(RelationGetPartitionDesc(parent));
+			get_default_oid_from_partdesc(RelationGetPartitionDesc(parent,
+																   false));
 		if (OidIsValid(defaultPartOid))
 			defaultRel = table_open(defaultPartOid, AccessExclusiveLock);
 
@@ -3266,7 +3274,7 @@ renameatt_internal(Oid myrelid,
 		 * expected_parents will only be 0 if we are not already recursing.
 		 */
 		if (expected_parents == 0 &&
-			find_inheritance_children(myrelid, NoLock) != NIL)
+			find_inheritance_children(myrelid, false, NoLock) != NIL)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 					 errmsg("inherited column \"%s\" must be renamed in child tables too",
@@ -3465,7 +3473,7 @@ rename_constraint_internal(Oid myrelid,
 		else
 		{
 			if (expected_parents == 0 &&
-				find_inheritance_children(myrelid, NoLock) != NIL)
+				find_inheritance_children(myrelid, false, NoLock) != NIL)
 				ereport(ERROR,
 						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 						 errmsg("inherited constraint \"%s\" must be renamed in child tables too",
@@ -4084,7 +4092,14 @@ AlterTableGetLockLevel(List *cmds)
 				break;
 
 			case AT_DetachPartition:
-				cmd_lockmode = AccessExclusiveLock;
+				if (((PartitionCmd *) cmd->def)->concurrent)
+					cmd_lockmode = ShareUpdateExclusiveLock;
+				else
+					cmd_lockmode = AccessExclusiveLock;
+				break;
+
+			case AT_DetachPartitionFinalize:
+				cmd_lockmode = ShareUpdateExclusiveLock;
 				break;
 
 			case AT_CheckNotNull:
@@ -4475,6 +4490,11 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			/* No command-specific prep needed */
 			pass = AT_PASS_MISC;
 			break;
+		case AT_DetachPartitionFinalize:
+			ATSimplePermissions(rel, ATT_TABLE);
+			/* No command-specific prep needed */
+			pass = AT_PASS_MISC;
+			break;
 		default:				/* oops */
 			elog(ERROR, "unrecognized alter table type: %d",
 				 (int) cmd->subtype);
@@ -4860,7 +4880,12 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 			Assert(cmd != NULL);
 			/* ATPrepCmd ensures it must be a table */
 			Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
-			ATExecDetachPartition(rel, ((PartitionCmd *) cmd->def)->name);
+			ATExecDetachPartition(wqueue, tab, rel,
+								  ((PartitionCmd *) cmd->def)->name,
+								  ((PartitionCmd *) cmd->def)->concurrent);
+			break;
+		case AT_DetachPartitionFinalize:
+			ATExecDetachPartitionFinalize(rel, ((PartitionCmd *) cmd->def)->name);
 			break;
 		case AT_AlterCollationRefreshVersion:
 			/* ATPrepCmd ensured it must be an index */
@@ -6292,7 +6317,7 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	 */
 	if (colDef->identity &&
 		recurse &&
-		find_inheritance_children(myrelid, NoLock) != NIL)
+		find_inheritance_children(myrelid, false, NoLock) != NIL)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 				 errmsg("cannot recursively add identity column to table that has child tables")));
@@ -6525,7 +6550,8 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	 * routines, we have to do this one level of recursion at a time; we can't
 	 * use find_all_inheritors to do it in one pass.
 	 */
-	children = find_inheritance_children(RelationGetRelid(rel), lockmode);
+	children =
+		find_inheritance_children(RelationGetRelid(rel), false, lockmode);
 
 	/*
 	 * If we are told not to recurse, there had better not be any child
@@ -6679,7 +6705,7 @@ ATPrepDropNotNull(Relation rel, bool recurse, bool recursing)
 	 */
 	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
 	{
-		PartitionDesc partdesc = RelationGetPartitionDesc(rel);
+		PartitionDesc partdesc = RelationGetPartitionDesc(rel, false);
 
 		Assert(partdesc != NULL);
 		if (partdesc->nparts > 0 && !recurse && !recursing)
@@ -6779,17 +6805,22 @@ ATExecDropNotNull(Relation rel, const char *colName, LOCKMODE lockmode)
 	if (rel->rd_rel->relispartition)
 	{
 		Oid			parentId = get_partition_parent(RelationGetRelid(rel));
-		Relation	parent = table_open(parentId, AccessShareLock);
-		TupleDesc	tupDesc = RelationGetDescr(parent);
+		Relation	parent;
+		TupleDesc	tupDesc;
 		AttrNumber	parent_attnum;
 
-		parent_attnum = get_attnum(parentId, colName);
-		if (TupleDescAttr(tupDesc, parent_attnum - 1)->attnotnull)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
-					 errmsg("column \"%s\" is marked NOT NULL in parent table",
-							colName)));
-		table_close(parent, AccessShareLock);
+		if (parentId != InvalidOid)
+		{
+			parent = table_open(parentId, AccessShareLock);
+			tupDesc = RelationGetDescr(parent);
+			parent_attnum = get_attnum(parentId, colName);
+			if (TupleDescAttr(tupDesc, parent_attnum - 1)->attnotnull)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+						 errmsg("column \"%s\" is marked NOT NULL in parent table",
+								colName)));
+			table_close(parent, AccessShareLock);
+		}
 	}
 
 	/*
@@ -7388,7 +7419,7 @@ ATPrepDropExpression(Relation rel, AlterTableCmd *cmd, bool recurse, bool recurs
 	 * resulting state can be properly dumped and restored.
 	 */
 	if (!recurse &&
-		find_inheritance_children(RelationGetRelid(rel), lockmode))
+		find_inheritance_children(RelationGetRelid(rel), false, lockmode))
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("ALTER TABLE / DROP EXPRESSION must be applied to child tables too")));
@@ -7971,7 +8002,8 @@ ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
 	 * routines, we have to do this one level of recursion at a time; we can't
 	 * use find_all_inheritors to do it in one pass.
 	 */
-	children = find_inheritance_children(RelationGetRelid(rel), lockmode);
+	children =
+		find_inheritance_children(RelationGetRelid(rel), false, lockmode);
 
 	if (children)
 	{
@@ -8435,7 +8467,8 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	 * routines, we have to do this one level of recursion at a time; we can't
 	 * use find_all_inheritors to do it in one pass.
 	 */
-	children = find_inheritance_children(RelationGetRelid(rel), lockmode);
+	children =
+		find_inheritance_children(RelationGetRelid(rel), false, lockmode);
 
 	/*
 	 * Check if ONLY was specified with ALTER TABLE.  If so, allow the
@@ -9050,7 +9083,7 @@ addFkRecurseReferenced(List **wqueue, Constraint *fkconstraint, Relation rel,
 	 */
 	if (pkrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
 	{
-		PartitionDesc pd = RelationGetPartitionDesc(pkrel);
+		PartitionDesc pd = RelationGetPartitionDesc(pkrel, false);
 
 		for (int i = 0; i < pd->nparts; i++)
 		{
@@ -9184,7 +9217,7 @@ addFkRecurseReferencing(List **wqueue, Constraint *fkconstraint, Relation rel,
 	}
 	else if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
 	{
-		PartitionDesc pd = RelationGetPartitionDesc(rel);
+		PartitionDesc pd = RelationGetPartitionDesc(rel, false);
 
 		/*
 		 * Recurse to take appropriate action on each partition; either we
@@ -10968,7 +11001,8 @@ ATExecDropConstraint(Relation rel, const char *constrName,
 	 * use find_all_inheritors to do it in one pass.
 	 */
 	if (!is_no_inherit_constraint)
-		children = find_inheritance_children(RelationGetRelid(rel), lockmode);
+		children =
+			find_inheritance_children(RelationGetRelid(rel), false, lockmode);
 	else
 		children = NIL;
 
@@ -11352,7 +11386,8 @@ ATPrepAlterColumnType(List **wqueue,
 		}
 	}
 	else if (!recursing &&
-			 find_inheritance_children(RelationGetRelid(rel), NoLock) != NIL)
+			 find_inheritance_children(RelationGetRelid(rel), false,
+									   NoLock) != NIL)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 				 errmsg("type of inherited column \"%s\" must be changed in child tables too",
@@ -14173,7 +14208,7 @@ ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode)
 	 */
 
 	/* Off to RemoveInheritance() where most of the work happens */
-	RemoveInheritance(rel, parent_rel);
+	RemoveInheritance(rel, parent_rel, false);
 
 	ObjectAddressSet(address, RelationRelationId,
 					 RelationGetRelid(parent_rel));
@@ -14184,12 +14219,70 @@ ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode)
 	return address;
 }
 
+/*
+ * MarkInheritDetached
+ *
+ * When a partition is detached from its parent concurrently, we don't
+ * remove the pg_inherits row until a second transaction; as a preparatory
+ * step, this function marks the entry as 'detached', so that other
+ * transactions know to ignore the partition.
+ */
+static void
+MarkInheritDetached(Relation child_rel, Relation parent_rel)
+{
+	Relation	catalogRelation;
+	SysScanDesc	scan;
+	ScanKeyData key;
+	HeapTuple	inheritsTuple;
+	bool		found = false;
+
+	/*
+	 * Find pg_inherits entries by inhrelid.
+	 */
+	catalogRelation = table_open(InheritsRelationId, RowExclusiveLock);
+	ScanKeyInit(&key,
+				Anum_pg_inherits_inhrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(RelationGetRelid(child_rel)));
+	scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
+							  true, NULL, 1, &key);
+
+	while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
+	{
+		HeapTuple	newtup;
+
+		if (((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhparent !=
+			RelationGetRelid(parent_rel))
+			elog(ERROR, "bad parent tuple found for partition %u",
+				 RelationGetRelid(child_rel));
+
+		newtup = heap_copytuple(inheritsTuple);
+		((Form_pg_inherits) GETSTRUCT(newtup))->inhdetached = true;
+
+		CatalogTupleUpdate(catalogRelation,
+						   &inheritsTuple->t_self,
+						   newtup);
+		found = true;
+	}
+
+	/* Done */
+	systable_endscan(scan);
+	table_close(catalogRelation, RowExclusiveLock);
+
+	if (!found)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_TABLE),
+				 errmsg("relation \"%s\" is not a partition of relation \"%s\"",
+						RelationGetRelationName(child_rel),
+						RelationGetRelationName(parent_rel))));
+}
+
 /*
  * RemoveInheritance
  *
  * Drop a parent from the child's parents. This just adjusts the attinhcount
  * and attislocal of the columns and removes the pg_inherit and pg_depend
- * entries.
+ * entries.  expect_detached is passed down to DeleteInheritsTuple, q.v..
  *
  * If attinhcount goes to 0 then attislocal gets set to true. If it goes back
  * up attislocal stays true, which means if a child is ever removed from a
@@ -14203,7 +14296,7 @@ ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode)
  * Common to ATExecDropInherit() and ATExecDetachPartition().
  */
 static void
-RemoveInheritance(Relation child_rel, Relation parent_rel)
+RemoveInheritance(Relation child_rel, Relation parent_rel, bool expect_detached)
 {
 	Relation	catalogRelation;
 	SysScanDesc scan;
@@ -14219,7 +14312,9 @@ RemoveInheritance(Relation child_rel, Relation parent_rel)
 		child_is_partition = true;
 
 	found = DeleteInheritsTuple(RelationGetRelid(child_rel),
-								RelationGetRelid(parent_rel));
+								RelationGetRelid(parent_rel),
+								expect_detached,
+								RelationGetRelationName(child_rel));
 	if (!found)
 	{
 		if (child_is_partition)
@@ -16327,7 +16422,7 @@ QueuePartitionConstraintValidation(List **wqueue, Relation scanrel,
 	}
 	else if (scanrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
 	{
-		PartitionDesc partdesc = RelationGetPartitionDesc(scanrel);
+		PartitionDesc partdesc = RelationGetPartitionDesc(scanrel, false);
 		int			i;
 
 		for (i = 0; i < partdesc->nparts; i++)
@@ -16387,7 +16482,7 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd,
 	 * new partition will change its partition constraint.
 	 */
 	defaultPartOid =
-		get_default_oid_from_partdesc(RelationGetPartitionDesc(rel));
+		get_default_oid_from_partdesc(RelationGetPartitionDesc(rel, false));
 	if (OidIsValid(defaultPartOid))
 		LockRelationOid(defaultPartOid, AccessExclusiveLock);
 
@@ -16976,105 +17071,230 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
  * ALTER TABLE DETACH PARTITION
  *
  * Return the address of the relation that is no longer a partition of rel.
+ *
+ * If concurrent mode is requested, we run in two transactions.  A side-
+ * effect is that this command cannot run in a multi-part ALTER TABLE.
+ * Currently, that's enforced by the grammar.
+ *
+ * The strategy for concurrency is to first modify the partition catalog
+ * rows to make it visible to everyone that the partition is detached,
+ * lock the partition against writes, and commit the transaction; anyone
+ * who requests the partition descriptor from that point onwards has to
+ * ignore such a partition.  In a second transaction, we wait until all
+ * transactions that could have seen the partition as attached are gone,
+ * then we remove the rest of partition metadata (pg_inherits and
+ * pg_class.relpartbounds).
  */
 static ObjectAddress
-ATExecDetachPartition(Relation rel, RangeVar *name)
+ATExecDetachPartition(List **wqueue, AlteredTableInfo *tab, Relation rel,
+					  RangeVar *name, bool concurrent)
 {
-	Relation	partRel,
-				classRel;
-	HeapTuple	tuple,
-				newtuple;
-	Datum		new_val[Natts_pg_class];
-	bool		new_null[Natts_pg_class],
-				new_repl[Natts_pg_class];
+	Relation	partRel;
 	ObjectAddress address;
 	Oid			defaultPartOid;
-	List	   *indexes;
-	List	   *fks;
-	ListCell   *cell;
 
 	/*
 	 * We must lock the default partition, because detaching this partition
 	 * will change its partition constraint.
 	 */
 	defaultPartOid =
-		get_default_oid_from_partdesc(RelationGetPartitionDesc(rel));
-	if (OidIsValid(defaultPartOid))
-		LockRelationOid(defaultPartOid, AccessExclusiveLock);
-
-	partRel = table_openrv(name, ShareUpdateExclusiveLock);
-
-	/* Ensure that foreign keys still hold after this detach */
-	ATDetachCheckNoForeignKeyRefs(partRel);
-
-	/* All inheritance related checks are performed within the function */
-	RemoveInheritance(partRel, rel);
-
-	/* Update pg_class tuple */
-	classRel = table_open(RelationRelationId, RowExclusiveLock);
-	tuple = SearchSysCacheCopy1(RELOID,
-								ObjectIdGetDatum(RelationGetRelid(partRel)));
-	if (!HeapTupleIsValid(tuple))
-		elog(ERROR, "cache lookup failed for relation %u",
-			 RelationGetRelid(partRel));
-	Assert(((Form_pg_class) GETSTRUCT(tuple))->relispartition);
-
-	/* Clear relpartbound and reset relispartition */
-	memset(new_val, 0, sizeof(new_val));
-	memset(new_null, false, sizeof(new_null));
-	memset(new_repl, false, sizeof(new_repl));
-	new_val[Anum_pg_class_relpartbound - 1] = (Datum) 0;
-	new_null[Anum_pg_class_relpartbound - 1] = true;
-	new_repl[Anum_pg_class_relpartbound - 1] = true;
-	newtuple = heap_modify_tuple(tuple, RelationGetDescr(classRel),
-								 new_val, new_null, new_repl);
-
-	((Form_pg_class) GETSTRUCT(newtuple))->relispartition = false;
-	CatalogTupleUpdate(classRel, &newtuple->t_self, newtuple);
-	heap_freetuple(newtuple);
-
+		get_default_oid_from_partdesc(RelationGetPartitionDesc(rel, false));
 	if (OidIsValid(defaultPartOid))
 	{
 		/*
-		 * If the relation being detached is the default partition itself,
-		 * remove it from the parent's pg_partitioned_table entry.
+		 * Concurrent detaching when a default partition exists is not
+		 * supported. The main problem is that the default partition
+		 * constraint would change.  And there's a definitional problem: what
+		 * should happen to the tuples that are being inserted that belong to
+		 * the partition being detached?  Putting them on the partition being
+		 * detached would be wrong, since they'd become "lost" after the but
+		 * we cannot put them in the default partition either until we alter
+		 * its partition constraint.
 		 *
-		 * If not, we must invalidate default partition's relcache entry, as
-		 * in StorePartitionBound: its partition constraint depends on every
-		 * other partition's partition constraint.
+		 * I think we could solve this problem if we effected the constraint
+		 * change before committing the first transaction.  But the lock would
+		 * have to remain AEL and it would cause concurrent query planning to
+		 * be blocked, so changing it that way would be even worse.
 		 */
-		if (RelationGetRelid(partRel) == defaultPartOid)
-			update_default_partition_oid(RelationGetRelid(rel), InvalidOid);
-		else
-			CacheInvalidateRelcacheByRelid(defaultPartOid);
+		if (concurrent)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("cannot detach partitions concurrently when a default partition exists")));
+		LockRelationOid(defaultPartOid, AccessExclusiveLock);
 	}
 
-	/* detach indexes too */
-	indexes = RelationGetIndexList(partRel);
-	foreach(cell, indexes)
+	/*
+	 * In concurrent mode, the partition is locked with share-update-exclusive
+	 * in the first transaction.  This allows concurrent transactions to be
+	 * doing DML to the partition.
+	 */
+	partRel = table_openrv(name, concurrent ? ShareLock :
+						   AccessExclusiveLock);
+
+	/*
+	 * Check inheritance conditions and either delete the pg_inherits row
+	 * (in non-concurrent mode) or just set the inhisdetached flag.
+	 */
+	if (!concurrent)
+		RemoveInheritance(partRel, rel, false);
+	else
+		MarkInheritDetached(partRel, rel);
+
+	/*
+	 * Ensure that foreign keys still hold after this detach.  This keeps
+	 * locks on the referencing tables, which prevents concurrent transactions
+	 * from adding rows that we wouldn't see.  For this to work in concurrent
+	 * mode, it is critical that the partition appears as no longer attached
+	 * for the RI queries as soon as the first transaction commits.
+	 */
+	ATDetachCheckNoForeignKeyRefs(partRel);
+
+	/*
+	 * Concurrent mode has to work harder; first we add a new constraint to the
+	 * partition that matches the partition constraint, if there isn't a matching
+	 * one already.  The reason for this is that the planner may have made
+	 * optimizations that depend on the constraint.  XXX Isn't it sufficient to
+	 * invalidate the partition's relcache entry?
+	 *
+	 * Then we close our existing transaction, and in a new one wait for
+	 * all processes to catch up on the catalog updates we've done so far; at
+	 * that point we can complete the operation.
+	 */
+	if (concurrent)
 	{
-		Oid			idxid = lfirst_oid(cell);
-		Relation	idx;
-		Oid			constrOid;
+		Oid		partrelid,
+				parentrelid;
+		LOCKTAG		tag;
+		char   *parentrelname;
+		char   *partrelname;
 
-		if (!has_superclass(idxid))
-			continue;
+		/* Add constraint, if needed. XXX hopefully we can just remove this */
+		DetachAddConstraintIfNeeded(wqueue, partRel);
 
-		Assert((IndexGetRelation(get_partition_parent(idxid), false) ==
-				RelationGetRelid(rel)));
+		/*
+		 * We're almost done now; the only traces that remain are the
+		 * pg_inherits tuple and the partition's relpartbounds.  Before we can
+		 * remove those, we need to wait until all transactions that know that
+		 * this is a partition are gone.
+		 */
 
-		idx = index_open(idxid, AccessExclusiveLock);
-		IndexSetParentIndex(idx, InvalidOid);
+		/*
+		 * Remember relation OIDs to re-acquire them later; and relation names
+		 * too, for error messages if something is dropped in between.
+		 */
+		partrelid = RelationGetRelid(partRel);
+		parentrelid = RelationGetRelid(rel);
+		parentrelname = MemoryContextStrdup(PortalContext,
+											RelationGetRelationName(rel));
+		partrelname = MemoryContextStrdup(PortalContext,
+										  RelationGetRelationName(partRel));
 
-		/* If there's a constraint associated with the index, detach it too */
-		constrOid = get_relation_idx_constraint_oid(RelationGetRelid(partRel),
-													idxid);
-		if (OidIsValid(constrOid))
-			ConstraintSetParentConstraint(constrOid, InvalidOid, InvalidOid);
+		/* Invalidate relcache entries for the parent -- must be before close */
+		CacheInvalidateRelcache(rel);
+
+		table_close(partRel, NoLock);
+		table_close(rel, NoLock);
+		tab->rel = NULL;
+
+		/* Make updated catalog entry visible */
+		PopActiveSnapshot();
+		CommitTransactionCommand();
+
+		StartTransactionCommand();
+
+		/*
+		 * Now wait.  This ensures that all queries that were planned including
+		 * the partition are finished before we remove the rest of catalog
+		 * entries.  We don't need or indeed want to acquire this lock, though
+		 * -- that would block later queries.
+		 *
+		 * We don't need to concern ourselves with waiting for a lock on the
+		 * partition itself, since we will acquire AccessExclusiveLock below.
+		 */
+		SET_LOCKTAG_RELATION(tag, MyDatabaseId, parentrelid);
+		WaitForLockersMultiple(list_make1(&tag), AccessExclusiveLock, false);
+
+		/*
+		 * Now acquire locks in both relations again.  Note they may have been
+		 * removed in the meantime, so care is required.
+		 */
+		rel = try_relation_open(parentrelid, ShareUpdateExclusiveLock);
+		partRel = try_relation_open(partrelid, AccessExclusiveLock);
+
+		/* If the relations aren't there, something bad happened; bail out */
+		if (rel == NULL)
+		{
+			if (partRel != NULL)	/* shouldn't happen */
+				elog(WARNING, "dangling partition \"%s\" remains, can't fix",
+					 partrelname);
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("partitioned table \"%s\" was removed concurrently",
+							parentrelname)));
+		}
+		if (partRel == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("partition \"%s\" was removed concurrently", partrelname)));
+
+		tab->rel = rel;
 
-		index_close(idx, NoLock);
 	}
-	table_close(classRel, RowExclusiveLock);
+
+	/* Do the final part of detaching */
+	DetachPartitionFinalize(rel, partRel, concurrent, defaultPartOid, false);
+
+	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(partRel));
+
+	/* keep our lock until commit */
+	table_close(partRel, NoLock);
+
+	return address;
+}
+
+/*
+ * Second part of ALTER TABLE .. DETACH.
+ *
+ * This is separate so that it can be run independently when the second
+ * transaction of the concurrent algorithm fails (crash or abort).
+ */
+static void
+DetachPartitionFinalize(Relation rel, Relation partRel, bool concurrent,
+						Oid defaultPartOid, bool wait)
+{
+	Relation	classRel;
+	List	   *fks;
+	ListCell   *cell;
+	List	   *indexes;
+	Datum		new_val[Natts_pg_class];
+	bool		new_null[Natts_pg_class],
+				new_repl[Natts_pg_class];
+	HeapTuple	tuple,
+				newtuple;
+
+	/*
+	 * If asked to, wait until existing snapshots are gone.  This is important
+	 * if the second transaction of DETACH PARTITION CONCURRENTLY is canceled:
+	 * the user could immediately run DETACH FINALIZE without actually waiting
+	 * for existing transactions.  We must not complete the detach action until
+	 * all such queries are complete (otherwise we would present them with an
+	 * inconsistent view of catalogs).
+	 */
+	if (wait)
+	{
+		Snapshot	snap = GetActiveSnapshot();
+
+		WaitForOlderSnapshots(snap->xmin, false);
+	}
+
+	if (concurrent)
+	{
+		/*
+		 * We can remove the pg_inherits row now. (In the non-concurrent case,
+		 * this was already done).
+		 */
+		RemoveInheritance(partRel, rel, true);
+	}
 
 	/* Drop any triggers that were cloned on creation/attach. */
 	DropClonedTriggersFromPartition(RelationGetRelid(partRel));
@@ -17147,22 +17367,150 @@ ATExecDetachPartition(Relation rel, RangeVar *name)
 		ObjectAddressSet(constraint, ConstraintRelationId, constrOid);
 		performDeletion(&constraint, DROP_RESTRICT, 0);
 	}
-	CommandCounterIncrement();
+
+	/* Now we can detach indexes */
+	indexes = RelationGetIndexList(partRel);
+	foreach(cell, indexes)
+	{
+		Oid			idxid = lfirst_oid(cell);
+		Relation	idx;
+		Oid			constrOid;
+
+		if (!has_superclass(idxid))
+			continue;
+
+		Assert((IndexGetRelation(get_partition_parent(idxid), false) ==
+				RelationGetRelid(rel)));
+
+		idx = index_open(idxid, AccessExclusiveLock);
+		IndexSetParentIndex(idx, InvalidOid);
+
+		/* If there's a constraint associated with the index, detach it too */
+		constrOid = get_relation_idx_constraint_oid(RelationGetRelid(partRel),
+													idxid);
+		if (OidIsValid(constrOid))
+			ConstraintSetParentConstraint(constrOid, InvalidOid, InvalidOid);
+
+		index_close(idx, NoLock);
+	}
+
+	/* Update pg_class tuple */
+	classRel = table_open(RelationRelationId, RowExclusiveLock);
+	tuple = SearchSysCacheCopy1(RELOID,
+								ObjectIdGetDatum(RelationGetRelid(partRel)));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for relation %u",
+			 RelationGetRelid(partRel));
+	Assert(((Form_pg_class) GETSTRUCT(tuple))->relispartition);
+
+	/* Clear relpartbound and reset relispartition */
+	memset(new_val, 0, sizeof(new_val));
+	memset(new_null, false, sizeof(new_null));
+	memset(new_repl, false, sizeof(new_repl));
+	new_val[Anum_pg_class_relpartbound - 1] = (Datum) 0;
+	new_null[Anum_pg_class_relpartbound - 1] = true;
+	new_repl[Anum_pg_class_relpartbound - 1] = true;
+	newtuple = heap_modify_tuple(tuple, RelationGetDescr(classRel),
+								 new_val, new_null, new_repl);
+
+	((Form_pg_class) GETSTRUCT(newtuple))->relispartition = false;
+	CatalogTupleUpdate(classRel, &newtuple->t_self, newtuple);
+	heap_freetuple(newtuple);
+	table_close(classRel, RowExclusiveLock);
+
+	if (OidIsValid(defaultPartOid))
+	{
+		/*
+		 * If the relation being detached is the default partition itself,
+		 * remove it from the parent's pg_partitioned_table entry.
+		 *
+		 * If not, we must invalidate default partition's relcache entry, as
+		 * in StorePartitionBound: its partition constraint depends on every
+		 * other partition's partition constraint.
+		 */
+		if (RelationGetRelid(partRel) == defaultPartOid)
+			update_default_partition_oid(RelationGetRelid(rel), InvalidOid);
+		else
+			CacheInvalidateRelcacheByRelid(defaultPartOid);
+	}
 
 	/*
 	 * Invalidate the parent's relcache so that the partition is no longer
 	 * included in its partition descriptor.
 	 */
 	CacheInvalidateRelcache(rel);
+}
+
+/*
+ * ALTER TABLE ... DETACH PARTITION ... FINALIZE
+ *
+ * To use when a DETACH PARTITION command previously did not run to
+ * completion; this completes the detaching process.
+ */
+static ObjectAddress
+ATExecDetachPartitionFinalize(Relation rel, RangeVar *name)
+{
+	Relation    partRel;
+	ObjectAddress address;
+
+	partRel = table_openrv(name, AccessExclusiveLock);
+
+	DetachPartitionFinalize(rel, partRel, true, InvalidOid, true);
 
 	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(partRel));
 
-	/* keep our lock until commit */
 	table_close(partRel, NoLock);
 
 	return address;
 }
 
+/*
+ * DetachAddConstraintIfNeeded
+ *		Subroutine for ATExecDetachPartition.  Create a constraint that
+ *		takes the place of the partition constraint, but avoid creating
+ *		a dupe if an equivalent constraint already exists.
+ */
+static void
+DetachAddConstraintIfNeeded(List **wqueue, Relation partRel)
+{
+	AlteredTableInfo *tab;
+	Expr	   *constraintExpr;
+	TupleDesc	td = RelationGetDescr(partRel);
+	Constraint *n;
+
+	constraintExpr = make_ands_explicit(RelationGetPartitionQual(partRel));
+
+	/* If an identical constraint exists, we don't need to create one */
+	if (td->constr && td->constr->num_check > 0)
+	{
+		for (int i = 0; i < td->constr->num_check; i++)
+		{
+			Node	*thisconstr;
+
+			thisconstr = stringToNode(td->constr->check[i].ccbin);
+
+			if (equal(constraintExpr, thisconstr))
+				return;
+		}
+	}
+
+	tab = ATGetQueueEntry(wqueue, partRel);
+
+	/* Add constraint on partition, equivalent to the partition constraint */
+	n = makeNode(Constraint);
+	n->contype = CONSTR_CHECK;
+	n->conname = NULL;
+	n->location = -1;
+	n->is_no_inherit = false;
+	n->raw_expr = NULL;
+	n->cooked_expr = nodeToString(constraintExpr);
+	n->initially_valid = true;
+	n->skip_validation = true;
+	/* It's a re-add, since it nominally already exists */
+	ATAddCheckConstraint(wqueue, tab, partRel, n,
+						 true, false, true, ShareUpdateExclusiveLock);
+}
+
 /*
  * DropClonedTriggersFromPartition
  *		subroutine for ATExecDetachPartition to remove any triggers that were
@@ -17358,7 +17706,7 @@ ATExecAttachPartitionIdx(List **wqueue, Relation parentIdx, RangeVar *name)
 							   RelationGetRelationName(partIdx))));
 
 		/* Make sure it indexes a partition of the other index's table */
-		partDesc = RelationGetPartitionDesc(parentTbl);
+		partDesc = RelationGetPartitionDesc(parentTbl, false);
 		found = false;
 		for (i = 0; i < partDesc->nparts; i++)
 		{
@@ -17512,7 +17860,7 @@ validatePartitionedIndex(Relation partedIdx, Relation partedTbl)
 	 * If we found as many inherited indexes as the partitioned table has
 	 * partitions, we're good; update pg_index to set indisvalid.
 	 */
-	if (tuples == RelationGetPartitionDesc(partedTbl)->nparts)
+	if (tuples == RelationGetPartitionDesc(partedTbl, false)->nparts)
 	{
 		Relation	idxRel;
 		HeapTuple	newtup;
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 8908847c6c..fb2cdbad6d 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -1119,7 +1119,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
 	 */
 	if (partition_recurse)
 	{
-		PartitionDesc partdesc = RelationGetPartitionDesc(rel);
+		PartitionDesc partdesc = RelationGetPartitionDesc(rel, false);
 		List	   *idxs = NIL;
 		List	   *childTbls = NIL;
 		ListCell   *l;
@@ -1141,7 +1141,8 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
 			ListCell   *l;
 			List	   *idxs = NIL;
 
-			idxs = find_inheritance_children(indexOid, ShareRowExclusiveLock);
+			idxs = find_inheritance_children(indexOid, false,
+											 ShareRowExclusiveLock);
 			foreach(l, idxs)
 				childTbls = lappend_oid(childTbls,
 										IndexGetRelation(lfirst_oid(l),
diff --git a/src/backend/executor/execPartition.c b/src/backend/executor/execPartition.c
index b8da4c5967..619aaffae4 100644
--- a/src/backend/executor/execPartition.c
+++ b/src/backend/executor/execPartition.c
@@ -569,6 +569,7 @@ ExecInitPartitionInfo(ModifyTableState *mtstate, EState *estate,
 					  int partidx)
 {
 	ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
+	Oid			partOid = dispatch->partdesc->oids[partidx];
 	Relation	partrel;
 	int			firstVarno = mtstate->resultRelInfo[0].ri_RangeTableIndex;
 	Relation	firstResultRel = mtstate->resultRelInfo[0].ri_RelationDesc;
@@ -579,7 +580,7 @@ ExecInitPartitionInfo(ModifyTableState *mtstate, EState *estate,
 
 	oldcxt = MemoryContextSwitchTo(proute->memcxt);
 
-	partrel = table_open(dispatch->partdesc->oids[partidx], RowExclusiveLock);
+	partrel = table_open(partOid, RowExclusiveLock);
 
 	leaf_part_rri = makeNode(ResultRelInfo);
 	InitResultRelInfo(leaf_part_rri,
@@ -1065,9 +1066,21 @@ ExecInitPartitionDispatchInfo(EState *estate,
 	int			dispatchidx;
 	MemoryContext oldcxt;
 
+	/*
+	 * For data modification, it is better that executor does not include
+	 * partitions being detached, except in snapshot-isolation mode.  This
+	 * means that a read-committed transaction immediately gets a "no
+	 * partition for tuple" error when a tuple is inserted into a partition
+	 * that's being detached concurrently, but a transaction in repeatable-
+	 * read mode can still use the partition.  Note that because partition
+	 * detach uses ShareLock on the partition (which conflicts with DML),
+	 * we're certain that the detach won't be able to complete until any
+	 * inserting transaction is done.
+	 */
 	if (estate->es_partition_directory == NULL)
 		estate->es_partition_directory =
-			CreatePartitionDirectory(estate->es_query_cxt);
+			CreatePartitionDirectory(estate->es_query_cxt,
+									 IsolationUsesXactSnapshot());
 
 	oldcxt = MemoryContextSwitchTo(proute->memcxt);
 
@@ -1645,9 +1658,10 @@ ExecCreatePartitionPruneState(PlanState *planstate,
 	ListCell   *lc;
 	int			i;
 
+	/* Executor must always include detached partitions */
 	if (estate->es_partition_directory == NULL)
 		estate->es_partition_directory =
-			CreatePartitionDirectory(estate->es_query_cxt);
+			CreatePartitionDirectory(estate->es_query_cxt, true);
 
 	n_part_hierarchies = list_length(partitionpruneinfo->prune_infos);
 	Assert(n_part_hierarchies > 0);
@@ -1713,9 +1727,12 @@ ExecCreatePartitionPruneState(PlanState *planstate,
 												partrel);
 
 			/*
-			 * Initialize the subplan_map and subpart_map.  Since detaching a
-			 * partition requires AccessExclusiveLock, no partitions can have
-			 * disappeared, nor can the bounds for any partition have changed.
+			 * Initialize the subplan_map and subpart_map.
+			 *
+			 * Because we request detached partitions to be included, and
+			 * detaching waits for old transactions, it is safe to assume that
+			 * no partitions have disappeared since this query was planned.
+			 *
 			 * However, new partitions may have been added.
 			 */
 			Assert(partdesc->nparts >= pinfo->nparts);
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 65bbc18ecb..1cd2931a74 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -4713,6 +4713,7 @@ _copyPartitionCmd(const PartitionCmd *from)
 
 	COPY_NODE_FIELD(name);
 	COPY_NODE_FIELD(bound);
+	COPY_SCALAR_FIELD(concurrent);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index c2d73626fc..250a23b347 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2972,6 +2972,7 @@ _equalPartitionCmd(const PartitionCmd *a, const PartitionCmd *b)
 {
 	COMPARE_NODE_FIELD(name);
 	COMPARE_NODE_FIELD(bound);
+	COMPARE_SCALAR_FIELD(concurrent);
 
 	return true;
 }
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 177e6e336a..87b21dcbdc 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -2136,10 +2136,17 @@ set_relation_partition_info(PlannerInfo *root, RelOptInfo *rel,
 {
 	PartitionDesc partdesc;
 
-	/* Create the PartitionDirectory infrastructure if we didn't already */
+	/*
+	 * Create the PartitionDirectory infrastructure if we didn't already.
+	 * In snapshot-isolation transactions, we always include detached
+	 * partitions, because otherwise they become invisible too soon.
+	 */
 	if (root->glob->partition_directory == NULL)
+	{
 		root->glob->partition_directory =
-			CreatePartitionDirectory(CurrentMemoryContext);
+			CreatePartitionDirectory(CurrentMemoryContext,
+									 IsolationUsesXactSnapshot());
+	}
 
 	partdesc = PartitionDirectoryLookup(root->glob->partition_directory,
 										relation);
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index dd72a9fc3c..6d2dc11b23 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -646,7 +646,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	EXCLUDE EXCLUDING EXCLUSIVE EXECUTE EXISTS EXPLAIN EXPRESSION
 	EXTENSION EXTERNAL EXTRACT
 
-	FALSE_P FAMILY FETCH FILTER FIRST_P FLOAT_P FOLLOWING FOR
+	FALSE_P FAMILY FETCH FILTER FINALIZE FIRST_P FLOAT_P FOLLOWING FOR
 	FORCE FOREIGN FORWARD FREEZE FROM FULL FUNCTION FUNCTIONS
 
 	GENERATED GLOBAL GRANT GRANTED GREATEST GROUP_P GROUPING GROUPS
@@ -2096,12 +2096,13 @@ partition_cmd:
 					n->subtype = AT_AttachPartition;
 					cmd->name = $3;
 					cmd->bound = $4;
+					cmd->concurrent = false;
 					n->def = (Node *) cmd;
 
 					$$ = (Node *) n;
 				}
-			/* ALTER TABLE <name> DETACH PARTITION <partition_name> */
-			| DETACH PARTITION qualified_name
+			/* ALTER TABLE <name> DETACH PARTITION <partition_name> [CONCURRENTLY] */
+			| DETACH PARTITION qualified_name opt_concurrently
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					PartitionCmd *cmd = makeNode(PartitionCmd);
@@ -2109,8 +2110,21 @@ partition_cmd:
 					n->subtype = AT_DetachPartition;
 					cmd->name = $3;
 					cmd->bound = NULL;
+					cmd->concurrent = $4;
 					n->def = (Node *) cmd;
 
+					$$ = (Node *) n;
+				}
+			| DETACH PARTITION qualified_name FINALIZE
+				{
+					AlterTableCmd *n = makeNode(AlterTableCmd);
+					PartitionCmd *cmd = makeNode(PartitionCmd);
+
+					n->subtype = AT_DetachPartitionFinalize;
+					cmd->name = $3;
+					cmd->bound = NULL;
+					cmd->concurrent = false;
+					n->def = (Node *) cmd;
 					$$ = (Node *) n;
 				}
 		;
@@ -2125,6 +2139,7 @@ index_partition_cmd:
 					n->subtype = AT_AttachPartition;
 					cmd->name = $3;
 					cmd->bound = NULL;
+					cmd->concurrent = false;
 					n->def = (Node *) cmd;
 
 					$$ = (Node *) n;
@@ -15337,6 +15352,7 @@ unreserved_keyword:
 			| EXTERNAL
 			| FAMILY
 			| FILTER
+			| FINALIZE
 			| FIRST_P
 			| FOLLOWING
 			| FORCE
@@ -15877,6 +15893,7 @@ bare_label_keyword:
 			| EXTRACT
 			| FALSE_P
 			| FAMILY
+			| FINALIZE
 			| FIRST_P
 			| FLOAT_P
 			| FOLLOWING
diff --git a/src/backend/partitioning/partbounds.c b/src/backend/partitioning/partbounds.c
index e5f3482d52..2b2b1dc1ad 100644
--- a/src/backend/partitioning/partbounds.c
+++ b/src/backend/partitioning/partbounds.c
@@ -2798,7 +2798,7 @@ check_new_partition_bound(char *relname, Relation parent,
 						  PartitionBoundSpec *spec, ParseState *pstate)
 {
 	PartitionKey key = RelationGetPartitionKey(parent);
-	PartitionDesc partdesc = RelationGetPartitionDesc(parent);
+	PartitionDesc partdesc = RelationGetPartitionDesc(parent, true);
 	PartitionBoundInfo boundinfo = partdesc->boundinfo;
 	int			with = -1;
 	bool		overlap = false;
@@ -3990,7 +3990,7 @@ get_qual_for_list(Relation parent, PartitionBoundSpec *spec)
 	{
 		int			i;
 		int			ndatums = 0;
-		PartitionDesc pdesc = RelationGetPartitionDesc(parent);
+		PartitionDesc pdesc = RelationGetPartitionDesc(parent, true);	/* XXX correct? */
 		PartitionBoundInfo boundinfo = pdesc->boundinfo;
 
 		if (boundinfo)
@@ -4190,7 +4190,7 @@ get_qual_for_range(Relation parent, PartitionBoundSpec *spec,
 	if (spec->is_default)
 	{
 		List	   *or_expr_args = NIL;
-		PartitionDesc pdesc = RelationGetPartitionDesc(parent);
+		PartitionDesc pdesc = RelationGetPartitionDesc(parent, true);	/* XXX correct? */
 		Oid		   *inhoids = pdesc->oids;
 		int			nparts = pdesc->nparts,
 					i;
diff --git a/src/backend/partitioning/partdesc.c b/src/backend/partitioning/partdesc.c
index f852b6e99d..58570fecfd 100644
--- a/src/backend/partitioning/partdesc.c
+++ b/src/backend/partitioning/partdesc.c
@@ -37,6 +37,7 @@ typedef struct PartitionDirectoryData
 {
 	MemoryContext pdir_mcxt;
 	HTAB	   *pdir_hash;
+	bool		include_detached;
 }			PartitionDirectoryData;
 
 typedef struct PartitionDirectoryEntry
@@ -46,7 +47,7 @@ typedef struct PartitionDirectoryEntry
 	PartitionDesc pd;
 } PartitionDirectoryEntry;
 
-static void RelationBuildPartitionDesc(Relation rel);
+static void RelationBuildPartitionDesc(Relation rel, bool include_detached);
 
 
 /*
@@ -61,13 +62,14 @@ static void RelationBuildPartitionDesc(Relation rel);
  * that the data doesn't become stale.
  */
 PartitionDesc
-RelationGetPartitionDesc(Relation rel)
+RelationGetPartitionDesc(Relation rel, bool include_detached)
 {
 	if (rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
 		return NULL;
 
-	if (unlikely(rel->rd_partdesc == NULL))
-		RelationBuildPartitionDesc(rel);
+	if (unlikely(rel->rd_partdesc == NULL ||
+				 rel->rd_partdesc->includes_detached != include_detached))
+		RelationBuildPartitionDesc(rel, include_detached);
 
 	return rel->rd_partdesc;
 }
@@ -88,7 +90,7 @@ RelationGetPartitionDesc(Relation rel)
  * permanently.
  */
 static void
-RelationBuildPartitionDesc(Relation rel)
+RelationBuildPartitionDesc(Relation rel, bool include_detached)
 {
 	PartitionDesc partdesc;
 	PartitionBoundInfo boundinfo = NULL;
@@ -110,7 +112,8 @@ RelationBuildPartitionDesc(Relation rel)
 	 * concurrently, whatever this function returns will be accurate as of
 	 * some well-defined point in time.
 	 */
-	inhoids = find_inheritance_children(RelationGetRelid(rel), NoLock);
+	inhoids = find_inheritance_children(RelationGetRelid(rel), include_detached,
+										NoLock);
 	nparts = list_length(inhoids);
 
 	/* Allocate working arrays for OIDs, leaf flags, and boundspecs. */
@@ -238,6 +241,7 @@ RelationBuildPartitionDesc(Relation rel)
 		partdesc->boundinfo = partition_bounds_copy(boundinfo, key);
 		partdesc->oids = (Oid *) palloc(nparts * sizeof(Oid));
 		partdesc->is_leaf = (bool *) palloc(nparts * sizeof(bool));
+		partdesc->includes_detached = include_detached;
 
 		/*
 		 * Assign OIDs from the original array into mapped indexes of the
@@ -280,7 +284,7 @@ RelationBuildPartitionDesc(Relation rel)
  *		Create a new partition directory object.
  */
 PartitionDirectory
-CreatePartitionDirectory(MemoryContext mcxt)
+CreatePartitionDirectory(MemoryContext mcxt, bool include_detached)
 {
 	MemoryContext oldcontext = MemoryContextSwitchTo(mcxt);
 	PartitionDirectory pdir;
@@ -295,6 +299,7 @@ CreatePartitionDirectory(MemoryContext mcxt)
 
 	pdir->pdir_hash = hash_create("partition directory", 256, &ctl,
 								  HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+	pdir->include_detached = include_detached;
 
 	MemoryContextSwitchTo(oldcontext);
 	return pdir;
@@ -327,7 +332,7 @@ PartitionDirectoryLookup(PartitionDirectory pdir, Relation rel)
 		 */
 		RelationIncrementReferenceCount(rel);
 		pde->rel = rel;
-		pde->pd = RelationGetPartitionDesc(rel);
+		pde->pd = RelationGetPartitionDesc(rel, pdir->include_detached);
 		Assert(pde->pd != NULL);
 	}
 	return pde->pd;
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 05bb698cf4..729274b330 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1236,6 +1236,25 @@ ProcessUtilitySlow(ParseState *pstate,
 					AlterTableStmt *atstmt = (AlterTableStmt *) parsetree;
 					Oid			relid;
 					LOCKMODE	lockmode;
+					ListCell   *cell;
+
+					/*
+					 * Disallow ALTER TABLE .. DETACH CONCURRENTLY in a
+					 * transaction block or function.  (Perhaps it could be
+					 * allowed in a procedure, but don't hold your breath.)
+					 */
+					foreach(cell, atstmt->cmds)
+					{
+						AlterTableCmd *cmd = (AlterTableCmd *) lfirst(cell);
+
+						/* Disallow DETACH CONCURRENTLY in a transaction block */
+						if (cmd->subtype == AT_DetachPartition)
+						{
+							if (((PartitionCmd *) cmd->def)->concurrent)
+								PreventInTransactionBlock(isTopLevel,
+														  "ALTER TABLE ... DETACH CONCURRENTLY");
+						}
+					}
 
 					/*
 					 * Figure out lock mode, and acquire lock.  This also does
diff --git a/src/backend/utils/cache/partcache.c b/src/backend/utils/cache/partcache.c
index a6388d980e..74d85b89fb 100644
--- a/src/backend/utils/cache/partcache.c
+++ b/src/backend/utils/cache/partcache.c
@@ -341,6 +341,7 @@ generate_partition_qual(Relation rel)
 	bool		isnull;
 	List	   *my_qual = NIL,
 			   *result = NIL;
+	Oid			parentrelid;
 	Relation	parent;
 
 	/* Guard against stack overflow due to overly deep partition tree */
@@ -350,9 +351,19 @@ generate_partition_qual(Relation rel)
 	if (rel->rd_partcheckvalid)
 		return copyObject(rel->rd_partcheck);
 
+	/*
+	 * Obtain parent relid; if it's invalid, then the partition is being
+	 * detached
+	 */
+	parentrelid = get_partition_parent(RelationGetRelid(rel));
+	if (parentrelid == InvalidOid)
+	{
+		rel->rd_partcheckvalid = true;
+		return NIL;
+	}
+
 	/* Grab at least an AccessShareLock on the parent table */
-	parent = relation_open(get_partition_parent(RelationGetRelid(rel)),
-						   AccessShareLock);
+	parent = relation_open(parentrelid, AccessShareLock);
 
 	/* Get pg_class.relpartbound */
 	tuple = SearchSysCache1(RELOID, RelationGetRelid(rel));
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 20af5a92b4..a8d64014f0 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -2117,7 +2117,12 @@ describeOneTableDetails(const char *schemaname,
 
 		printfPQExpBuffer(&buf,
 						  "SELECT inhparent::pg_catalog.regclass,\n"
-						  "  pg_catalog.pg_get_expr(c.relpartbound, c.oid)");
+						  "  pg_catalog.pg_get_expr(c.relpartbound, c.oid),\n  ");
+
+		appendPQExpBuffer(&buf,
+						  pset.sversion >= 140000 ? "inhdetached" :
+						  "false as inhdetached");
+
 		/* If verbose, also request the partition constraint definition */
 		if (verbose)
 			appendPQExpBufferStr(&buf,
@@ -2135,17 +2140,19 @@ describeOneTableDetails(const char *schemaname,
 		{
 			char	   *parent_name = PQgetvalue(result, 0, 0);
 			char	   *partdef = PQgetvalue(result, 0, 1);
+			char	   *detached = PQgetvalue(result, 0, 2);
 
-			printfPQExpBuffer(&tmpbuf, _("Partition of: %s %s"), parent_name,
-							  partdef);
+			printfPQExpBuffer(&tmpbuf, _("Partition of: %s %s%s"), parent_name,
+							  partdef,
+							  strcmp(detached, "t") == 0 ? " DETACHED" : "");
 			printTableAddFooter(&cont, tmpbuf.data);
 
 			if (verbose)
 			{
 				char	   *partconstraintdef = NULL;
 
-				if (!PQgetisnull(result, 0, 2))
-					partconstraintdef = PQgetvalue(result, 0, 2);
+				if (!PQgetisnull(result, 0, 3))
+					partconstraintdef = PQgetvalue(result, 0, 3);
 				/* If there isn't any constraint, show that explicitly */
 				if (partconstraintdef == NULL || partconstraintdef[0] == '\0')
 					printfPQExpBuffer(&tmpbuf, _("No partition constraint"));
@@ -3197,9 +3204,18 @@ describeOneTableDetails(const char *schemaname,
 		}
 
 		/* print child tables (with additional info if partitions) */
-		if (pset.sversion >= 100000)
+		if (pset.sversion >= 140000)
 			printfPQExpBuffer(&buf,
-							  "SELECT c.oid::pg_catalog.regclass, c.relkind,"
+							  "SELECT c.oid::pg_catalog.regclass, c.relkind, inhdetached,"
+							  " pg_catalog.pg_get_expr(c.relpartbound, c.oid)\n"
+							  "FROM pg_catalog.pg_class c, pg_catalog.pg_inherits i\n"
+							  "WHERE c.oid = i.inhrelid AND i.inhparent = '%s'\n"
+							  "ORDER BY pg_catalog.pg_get_expr(c.relpartbound, c.oid) = 'DEFAULT',"
+							  " c.oid::pg_catalog.regclass::pg_catalog.text;",
+							  oid);
+		else if (pset.sversion >= 100000)
+			printfPQExpBuffer(&buf,
+							  "SELECT c.oid::pg_catalog.regclass, c.relkind, false AS inhdetached,"
 							  " pg_catalog.pg_get_expr(c.relpartbound, c.oid)\n"
 							  "FROM pg_catalog.pg_class c, pg_catalog.pg_inherits i\n"
 							  "WHERE c.oid = i.inhrelid AND i.inhparent = '%s'\n"
@@ -3208,14 +3224,14 @@ describeOneTableDetails(const char *schemaname,
 							  oid);
 		else if (pset.sversion >= 80300)
 			printfPQExpBuffer(&buf,
-							  "SELECT c.oid::pg_catalog.regclass, c.relkind, NULL\n"
+							  "SELECT c.oid::pg_catalog.regclass, c.relkind, false AS inhdetached, NULL\n"
 							  "FROM pg_catalog.pg_class c, pg_catalog.pg_inherits i\n"
 							  "WHERE c.oid = i.inhrelid AND i.inhparent = '%s'\n"
 							  "ORDER BY c.oid::pg_catalog.regclass::pg_catalog.text;",
 							  oid);
 		else
 			printfPQExpBuffer(&buf,
-							  "SELECT c.oid::pg_catalog.regclass, c.relkind, NULL\n"
+							  "SELECT c.oid::pg_catalog.regclass, c.relkind, false AS inhdetached, NULL\n"
 							  "FROM pg_catalog.pg_class c, pg_catalog.pg_inherits i\n"
 							  "WHERE c.oid = i.inhrelid AND i.inhparent = '%s'\n"
 							  "ORDER BY c.relname;",
@@ -3265,11 +3281,13 @@ describeOneTableDetails(const char *schemaname,
 				else
 					printfPQExpBuffer(&buf, "%*s  %s",
 									  ctw, "", PQgetvalue(result, i, 0));
-				if (!PQgetisnull(result, i, 2))
-					appendPQExpBuffer(&buf, " %s", PQgetvalue(result, i, 2));
+				if (!PQgetisnull(result, i, 3))
+					appendPQExpBuffer(&buf, " %s", PQgetvalue(result, i, 3));
 				if (child_relkind == RELKIND_PARTITIONED_TABLE ||
 					child_relkind == RELKIND_PARTITIONED_INDEX)
 					appendPQExpBufferStr(&buf, ", PARTITIONED");
+				if (strcmp(PQgetvalue(result, i, 2), "t") == 0)
+					appendPQExpBuffer(&buf, " (DETACHED)");
 				if (i < tuples - 1)
 					appendPQExpBufferChar(&buf, ',');
 
diff --git a/src/include/catalog/pg_inherits.h b/src/include/catalog/pg_inherits.h
index 2b71cad9a2..155596907c 100644
--- a/src/include/catalog/pg_inherits.h
+++ b/src/include/catalog/pg_inherits.h
@@ -34,6 +34,7 @@ CATALOG(pg_inherits,2611,InheritsRelationId)
 	Oid			inhrelid BKI_LOOKUP(pg_class);
 	Oid			inhparent BKI_LOOKUP(pg_class);
 	int32		inhseqno;
+	bool		inhdetached;
 } FormData_pg_inherits;
 
 /* ----------------
@@ -49,7 +50,8 @@ DECLARE_INDEX(pg_inherits_parent_index, 2187, on pg_inherits using btree(inhpare
 #define InheritsParentIndexId  2187
 
 
-extern List *find_inheritance_children(Oid parentrelId, LOCKMODE lockmode);
+extern List *find_inheritance_children(Oid parentrelId, bool include_detached,
+									   LOCKMODE lockmode);
 extern List *find_all_inheritors(Oid parentrelId, LOCKMODE lockmode,
 								 List **parents);
 extern bool has_subclass(Oid relationId);
@@ -57,6 +59,7 @@ extern bool has_superclass(Oid relationId);
 extern bool typeInheritsFrom(Oid subclassTypeId, Oid superclassTypeId);
 extern void StoreSingleInheritance(Oid relationId, Oid parentOid,
 								   int32 seqNumber);
-extern bool DeleteInheritsTuple(Oid inhrelid, Oid inhparent);
+extern bool DeleteInheritsTuple(Oid inhrelid, Oid inhparent, bool allow_detached,
+								const char *childname);
 
 #endif							/* PG_INHERITS_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 236832a2ca..f97105ed3a 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -860,6 +860,7 @@ typedef struct PartitionCmd
 	NodeTag		type;
 	RangeVar   *name;			/* name of partition to attach/detach */
 	PartitionBoundSpec *bound;	/* FOR VALUES, if attaching */
+	bool		concurrent;
 } PartitionCmd;
 
 /****************************************************************************
@@ -1896,6 +1897,7 @@ typedef enum AlterTableType
 	AT_GenericOptions,			/* OPTIONS (...) */
 	AT_AttachPartition,			/* ATTACH PARTITION */
 	AT_DetachPartition,			/* DETACH PARTITION */
+	AT_DetachPartitionFinalize,	/* DETACH PARTITION FINALIZE */
 	AT_AddIdentity,				/* ADD IDENTITY */
 	AT_SetIdentity,				/* SET identity column options */
 	AT_DropIdentity,			/* DROP IDENTITY */
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 28083aaac9..7da248a385 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -165,6 +165,7 @@ PG_KEYWORD("false", FALSE_P, RESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("family", FAMILY, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("fetch", FETCH, RESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("filter", FILTER, UNRESERVED_KEYWORD, AS_LABEL)
+PG_KEYWORD("finalize", FINALIZE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("first", FIRST_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("float", FLOAT_P, COL_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("following", FOLLOWING, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/partitioning/partdesc.h b/src/include/partitioning/partdesc.h
index ff113199e5..7f03ff4271 100644
--- a/src/include/partitioning/partdesc.h
+++ b/src/include/partitioning/partdesc.h
@@ -21,6 +21,7 @@
 typedef struct PartitionDescData
 {
 	int			nparts;			/* Number of partitions */
+	bool		includes_detached;	/* Does it include detached partitions */
 	Oid		   *oids;			/* Array of 'nparts' elements containing
 								 * partition OIDs in order of the their bounds */
 	bool	   *is_leaf;		/* Array of 'nparts' elements storing whether
@@ -30,9 +31,9 @@ typedef struct PartitionDescData
 } PartitionDescData;
 
 
-extern PartitionDesc RelationGetPartitionDesc(Relation rel);
+extern PartitionDesc RelationGetPartitionDesc(Relation rel, bool include_detached);
 
-extern PartitionDirectory CreatePartitionDirectory(MemoryContext mcxt);
+extern PartitionDirectory CreatePartitionDirectory(MemoryContext mcxt, bool include_detached);
 extern PartitionDesc PartitionDirectoryLookup(PartitionDirectory, Relation);
 extern void DestroyPartitionDirectory(PartitionDirectory pdir);
 
diff --git a/src/include/utils/snapmgr.h b/src/include/utils/snapmgr.h
index 2c8b881a09..901eccec25 100644
--- a/src/include/utils/snapmgr.h
+++ b/src/include/utils/snapmgr.h
@@ -133,6 +133,7 @@ extern void AtEOXact_Snapshot(bool isCommit, bool resetXmin);
 extern void ImportSnapshot(const char *idstr);
 extern bool XactHasExportedSnapshots(void);
 extern void DeleteAllExportedSnapshotFiles(void);
+extern void WaitForOlderSnapshots(TransactionId limitXmin, bool progress);
 extern bool ThereAreNoPriorRegisteredSnapshots(void);
 extern bool TransactionIdLimitedForOldSnapshots(TransactionId recentXmin,
 												Relation relation,
diff --git a/src/test/isolation/expected/detach-partition-concurrently-1.out b/src/test/isolation/expected/detach-partition-concurrently-1.out
new file mode 100644
index 0000000000..8d15beac60
--- /dev/null
+++ b/src/test/isolation/expected/detach-partition-concurrently-1.out
@@ -0,0 +1,301 @@
+Parsed test spec with 3 sessions
+
+starting permutation: s1b s1s s2detach s1s s1c s1s
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+
+starting permutation: s1b s1s s2detach s1s s3s s3i s1c s3i s2drop s1s
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+step s3s: SELECT * FROM d_listp;
+a              
+
+1              
+step s3i: SELECT relpartbound IS NULL FROM pg_class where relname = 'd_listp2';
+?column?       
+
+f              
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s3i: SELECT relpartbound IS NULL FROM pg_class where relname = 'd_listp2';
+?column?       
+
+t              
+step s2drop: DROP TABLE d_listp2;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+
+starting permutation: s1b s1s s2detach s1ins s1s s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1ins: INSERT INTO d_listp VALUES (1);
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+1              
+step s1c: COMMIT;
+step s2detach: <... completed>
+
+starting permutation: s1b s1s s1ins2 s2detach s1ins s1s s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1ins2: INSERT INTO d_listp VALUES (2);
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1ins: INSERT INTO d_listp VALUES (1);
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+1              
+2              
+2              
+step s1c: COMMIT;
+step s2detach: <... completed>
+
+starting permutation: s1brr s1s s2detach s1ins s1s s1c
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1ins: INSERT INTO d_listp VALUES (1);
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+1              
+2              
+step s1c: COMMIT;
+step s2detach: <... completed>
+
+starting permutation: s1brr s1s s2detach s1s s1c
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1c: COMMIT;
+step s2detach: <... completed>
+
+starting permutation: s1b s1ins2 s2detach s3ins2 s1c s3debugtest
+step s1b: BEGIN;
+step s1ins2: INSERT INTO d_listp VALUES (2);
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s3ins2: INSERT INTO d_listp VALUES (2); <waiting ...>
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s3ins2: <... completed>
+step s3debugtest: SELECT tableoid::regclass FROM d_listp; SELECT * from d_listp2;
+tableoid       
+
+d_listp1       
+a              
+
+2              
+2              
+2              
+
+starting permutation: s1brr s1prep s1s s2detach s1s s1exec1 s3s s1dealloc s1c
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1prep: PREPARE f(int) AS INSERT INTO d_listp VALUES ($1);
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1exec1: EXECUTE f(1);
+step s3s: SELECT * FROM d_listp;
+a              
+
+1              
+step s1dealloc: DEALLOCATE f;
+step s1c: COMMIT;
+step s2detach: <... completed>
+
+starting permutation: s1brr s1prep s1exec2 s2detach s1s s1exec2 s3s s1c s1dealloc
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1prep: PREPARE f(int) AS INSERT INTO d_listp VALUES ($1);
+step s1exec2: EXECUTE f(2);
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+2              
+step s1exec2: EXECUTE f(2);
+step s3s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s1dealloc: DEALLOCATE f;
+
+starting permutation: s1brr s1prep s1s s2detach s1s s1exec2 s1c s1dealloc
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1prep: PREPARE f(int) AS INSERT INTO d_listp VALUES ($1);
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1exec2: EXECUTE f(2);
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s1dealloc: DEALLOCATE f;
+
+starting permutation: s1brr s1prep s2detach s1s s1exec2 s1c s1dealloc
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1prep: PREPARE f(int) AS INSERT INTO d_listp VALUES ($1);
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1exec2: EXECUTE f(2);
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s1dealloc: DEALLOCATE f;
+
+starting permutation: s1brr s1prep1 s2detach s1s s1exec2 s1c s1dealloc
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1prep1: PREPARE f(int) AS INSERT INTO d_listp VALUES (1);
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1exec2: EXECUTE f(2);
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s1dealloc: DEALLOCATE f;
+
+starting permutation: s1brr s1prep2 s2detach s1s s1exec2 s1c s1dealloc
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1prep2: PREPARE f(int) AS INSERT INTO d_listp VALUES (2);
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s1exec2: EXECUTE f(2);
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s1dealloc: DEALLOCATE f;
+
+starting permutation: s1b s1s s2detach s3drop1 s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s3drop1: DROP TABLE d_listp; <waiting ...>
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s3drop1: <... completed>
+error in steps s1c s2detach s3drop1: ERROR:  partitioned table "d_listp" was removed concurrently
+
+starting permutation: s1b s1s s2detach s3drop2 s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s3drop2: DROP TABLE d_listp2; <waiting ...>
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s3drop2: <... completed>
+error in steps s1c s2detach s3drop2: ERROR:  partition "d_listp2" was removed concurrently
+
+starting permutation: s1b s1s s2detach s3detach s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s3detach: ALTER TABLE d_listp DETACH PARTITION d_listp2; <waiting ...>
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s3detach: <... completed>
+error in steps s1c s2detach s3detach: ERROR:  cannot detach partition "d_listp2"
+
+starting permutation: s1b s1s s2detach s3rename s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_listp;
+a              
+
+1              
+2              
+step s2detach: ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; <waiting ...>
+step s3rename: ALTER TABLE d_listp2 RENAME TO d_listp_foobar; <waiting ...>
+step s1c: COMMIT;
+step s2detach: <... completed>
+step s3rename: <... completed>
diff --git a/src/test/isolation/expected/detach-partition-concurrently-2.out b/src/test/isolation/expected/detach-partition-concurrently-2.out
new file mode 100644
index 0000000000..85be707b40
--- /dev/null
+++ b/src/test/isolation/expected/detach-partition-concurrently-2.out
@@ -0,0 +1,66 @@
+Parsed test spec with 3 sessions
+
+starting permutation: s1b s1s s2d s3i1 s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_lp_fk;
+a              
+
+1              
+2              
+step s2d: ALTER TABLE d_lp_fk DETACH PARTITION d_lp_fk_1 CONCURRENTLY; <waiting ...>
+step s3i1: INSERT INTO d_lp_fk_r VALUES (1);
+ERROR:  insert or update on table "d_lp_fk_r" violates foreign key constraint "d_lp_fk_r_a_fkey"
+step s1c: COMMIT;
+step s2d: <... completed>
+
+starting permutation: s1b s1s s2d s3i2 s3i2 s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_lp_fk;
+a              
+
+1              
+2              
+step s2d: ALTER TABLE d_lp_fk DETACH PARTITION d_lp_fk_1 CONCURRENTLY; <waiting ...>
+step s3i2: INSERT INTO d_lp_fk_r VALUES (2);
+step s3i2: INSERT INTO d_lp_fk_r VALUES (2);
+step s1c: COMMIT;
+step s2d: <... completed>
+
+starting permutation: s1b s1s s3i1 s2d s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_lp_fk;
+a              
+
+1              
+2              
+step s3i1: INSERT INTO d_lp_fk_r VALUES (1);
+step s2d: ALTER TABLE d_lp_fk DETACH PARTITION d_lp_fk_1 CONCURRENTLY;
+ERROR:  removing partition "d_lp_fk_1" violates foreign key constraint "d_lp_fk_r_a_fkey1"
+step s1c: COMMIT;
+
+starting permutation: s1b s1s s3i2 s2d s1c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_lp_fk;
+a              
+
+1              
+2              
+step s3i2: INSERT INTO d_lp_fk_r VALUES (2);
+step s2d: ALTER TABLE d_lp_fk DETACH PARTITION d_lp_fk_1 CONCURRENTLY; <waiting ...>
+step s1c: COMMIT;
+step s2d: <... completed>
+
+starting permutation: s1b s1s s3b s2d s3i1 s1c s3c
+step s1b: BEGIN;
+step s1s: SELECT * FROM d_lp_fk;
+a              
+
+1              
+2              
+step s3b: BEGIN;
+step s2d: ALTER TABLE d_lp_fk DETACH PARTITION d_lp_fk_1 CONCURRENTLY; <waiting ...>
+step s3i1: INSERT INTO d_lp_fk_r VALUES (1);
+ERROR:  insert or update on table "d_lp_fk_r" violates foreign key constraint "d_lp_fk_r_a_fkey"
+step s1c: COMMIT;
+step s2d: <... completed>
+step s3c: COMMIT;
diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule
index 5d6b79e66e..69928dc540 100644
--- a/src/test/isolation/isolation_schedule
+++ b/src/test/isolation/isolation_schedule
@@ -24,6 +24,8 @@ test: deadlock-hard
 test: deadlock-soft
 test: deadlock-soft-2
 test: deadlock-parallel
+test: detach-partition-concurrently-1
+test: detach-partition-concurrently-2
 test: fk-contention
 test: fk-deadlock
 test: fk-deadlock2
diff --git a/src/test/isolation/specs/detach-partition-concurrently-1.spec b/src/test/isolation/specs/detach-partition-concurrently-1.spec
new file mode 100644
index 0000000000..1e9bea8198
--- /dev/null
+++ b/src/test/isolation/specs/detach-partition-concurrently-1.spec
@@ -0,0 +1,90 @@
+# Test that detach partition concurrently makes the partition invisible at the
+# correct time.
+
+setup
+{
+  DROP TABLE IF EXISTS d_listp, d_listp1, d_listp2;
+  CREATE TABLE d_listp (a int) PARTITION BY LIST(a);
+  CREATE TABLE d_listp1 PARTITION OF d_listp FOR VALUES IN (1);
+  CREATE TABLE d_listp2 PARTITION OF d_listp FOR VALUES IN (2);
+  INSERT INTO d_listp VALUES (1),(2);
+}
+
+teardown {
+    DROP TABLE IF EXISTS d_listp, d_listp2, d_listp_foobar;
+}
+
+session "s1"
+step "s1b"		{ BEGIN; }
+step "s1brr"	{ BEGIN ISOLATION LEVEL REPEATABLE READ; }
+step "s1s"		{ SELECT * FROM d_listp; }
+step "s1ins"	{ INSERT INTO d_listp VALUES (1); }
+step "s1ins2"	{ INSERT INTO d_listp VALUES (2); }
+step "s1prep"	{ PREPARE f(int) AS INSERT INTO d_listp VALUES ($1); }
+step "s1prep1"	{ PREPARE f(int) AS INSERT INTO d_listp VALUES (1); }
+step "s1prep2"	{ PREPARE f(int) AS INSERT INTO d_listp VALUES (2); }
+step "s1exec1"	{ EXECUTE f(1); }
+step "s1exec2"	{ EXECUTE f(2); }
+step "s1dealloc" { DEALLOCATE f; }
+step "s1c"		{ COMMIT; }
+
+session "s2"
+step "s2detach"		{ ALTER TABLE d_listp DETACH PARTITION d_listp2 CONCURRENTLY; }
+step "s2drop"	{ DROP TABLE d_listp2; }
+
+session "s3"
+step "s3s"		{ SELECT * FROM d_listp; }
+step "s3i"		{ SELECT relpartbound IS NULL FROM pg_class where relname = 'd_listp2'; }
+step "s3ins2"		{ INSERT INTO d_listp VALUES (2); }
+step "s3drop1"	{ DROP TABLE d_listp; }
+step "s3drop2"	{ DROP TABLE d_listp2; }
+step "s3detach"	{ ALTER TABLE d_listp DETACH PARTITION d_listp2; }
+step "s3rename"	{ ALTER TABLE d_listp2 RENAME TO d_listp_foobar; }
+# XXX remove this step
+step "s3debugtest" { SELECT tableoid::regclass FROM d_listp; SELECT * from d_listp2; }
+
+# The transaction that detaches hangs until it sees any older transaction
+# terminate, as does anybody else.
+permutation "s1b" "s1s" "s2detach" "s1s" "s1c" "s1s"
+
+# relpartbound remains set until s1 commits
+# XXX this could be timing dependent :-(
+permutation "s1b" "s1s" "s2detach" "s1s" "s3s" "s3i" "s1c" "s3i" "s2drop" "s1s"
+
+# In read-committed mode, the partition disappears from view of concurrent
+# transactions immediately.  But if a write lock is held, then the detach
+# has to wait.
+permutation "s1b"   "s1s"          "s2detach" "s1ins" "s1s" "s1c"
+permutation "s1b"   "s1s" "s1ins2" "s2detach" "s1ins" "s1s" "s1c"
+
+# In repeatable-read mode, the partition remains visible until commit even
+# if the to-be-detached partition is not locked for write.
+permutation "s1brr" "s1s"          "s2detach" "s1ins" "s1s" "s1c"
+permutation "s1brr" "s1s"          "s2detach"         "s1s" "s1c"
+
+# Another process trying to acquire a write lock will be blocked behind the
+# detacher
+permutation "s1b" "s1ins2" "s2detach" "s3ins2" "s1c" "s3debugtest"
+
+# a prepared query is not blocked
+permutation "s1brr" "s1prep" "s1s" "s2detach" "s1s" "s1exec1" "s3s" "s1dealloc" "s1c"
+permutation "s1brr" "s1prep" "s1exec2" "s2detach" "s1s" "s1exec2" "s3s" "s1c" "s1dealloc"
+permutation "s1brr" "s1prep" "s1s" "s2detach" "s1s" "s1exec2" "s1c" "s1dealloc"
+permutation "s1brr" "s1prep" "s2detach" "s1s" "s1exec2" "s1c" "s1dealloc"
+permutation "s1brr" "s1prep1" "s2detach" "s1s" "s1exec2" "s1c" "s1dealloc"
+permutation "s1brr" "s1prep2" "s2detach" "s1s" "s1exec2" "s1c" "s1dealloc"
+
+
+# Note: the following tests are not very interesting in isolationtester because
+# the way this tool handles multiple sessions: it'll only run the drop/detach/
+# rename commands after s2 is blocked waiting.  It would be more useful to
+# run the DDL when s2 commits its first transaction instead.  Maybe these should
+# become TAP tests someday.
+
+# What happens if the partition or the parent table is dropped while waiting?
+permutation "s1b" "s1s" "s2detach" "s3drop1" "s1c"
+permutation "s1b" "s1s" "s2detach" "s3drop2" "s1c"
+# Also try a non-concurrent detach while the other one is waiting
+permutation "s1b" "s1s" "s2detach" "s3detach" "s1c"
+# and some other DDL
+permutation "s1b" "s1s" "s2detach" "s3rename" "s1c"
diff --git a/src/test/isolation/specs/detach-partition-concurrently-2.spec b/src/test/isolation/specs/detach-partition-concurrently-2.spec
new file mode 100644
index 0000000000..9281c80a69
--- /dev/null
+++ b/src/test/isolation/specs/detach-partition-concurrently-2.spec
@@ -0,0 +1,41 @@
+# Test that detach partition concurrently makes the partition safe
+# for foreign keys that reference it.
+
+setup
+{
+  DROP TABLE IF EXISTS d_lp_fk, d_lp_fk_1, d_lp_fk_2, d_lp_fk_r;
+
+  CREATE TABLE d_lp_fk (a int PRIMARY KEY) PARTITION BY LIST(a);
+  CREATE TABLE d_lp_fk_1 PARTITION OF d_lp_fk FOR VALUES IN (1);
+  CREATE TABLE d_lp_fk_2 PARTITION OF d_lp_fk FOR VALUES IN (2);
+  INSERT INTO d_lp_fk VALUES (1), (2);
+
+  CREATE TABLE d_lp_fk_r (a int references d_lp_fk);
+}
+
+teardown { DROP TABLE IF EXISTS d_lp_fk, d_lp_fk_1, d_lp_fk_2, d_lp_fk_r; }
+
+session "s1"
+step "s1b"		{ BEGIN; }
+step "s1s"		{ SELECT * FROM d_lp_fk; }
+step "s1c"		{ COMMIT; }
+
+session "s2"
+step "s2d"		{ ALTER TABLE d_lp_fk DETACH PARTITION d_lp_fk_1 CONCURRENTLY; }
+
+session "s3"
+step "s3b"		{ BEGIN; }
+step "s3i1"		{ INSERT INTO d_lp_fk_r VALUES (1); }
+step "s3i2"		{ INSERT INTO d_lp_fk_r VALUES (2); }
+step "s3c"		{ COMMIT; }
+
+# The transaction that detaches hangs until it sees any older transaction
+# terminate.
+permutation "s1b" "s1s" "s2d" "s3i1" "s1c"
+permutation "s1b" "s1s" "s2d" "s3i2" "s3i2" "s1c"
+
+permutation "s1b" "s1s" "s3i1" "s2d" "s1c"
+permutation "s1b" "s1s" "s3i2" "s2d" "s1c"
+
+# what if s3 has an uncommitted insertion?
+permutation "s1b" "s1s" "s3b" "s2d" "s3i1" "s1c" "s3c"
diff --git a/src/test/modules/delay_execution/Makefile b/src/test/modules/delay_execution/Makefile
index f270aebf3a..70f24e846d 100644
--- a/src/test/modules/delay_execution/Makefile
+++ b/src/test/modules/delay_execution/Makefile
@@ -7,7 +7,8 @@ OBJS = \
 	$(WIN32RES) \
 	delay_execution.o
 
-ISOLATION = partition-addition
+ISOLATION = partition-addition \
+	    partition-removal-1
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/src/test/modules/delay_execution/expected/partition-removal-1.out b/src/test/modules/delay_execution/expected/partition-removal-1.out
new file mode 100644
index 0000000000..00b93ecf65
--- /dev/null
+++ b/src/test/modules/delay_execution/expected/partition-removal-1.out
@@ -0,0 +1,79 @@
+Parsed test spec with 3 sessions
+
+starting permutation: s3lock s1b s1exec s2remp s3unlock s1c
+step s3lock: SELECT pg_advisory_lock(12543);
+pg_advisory_lock
+
+               
+step s1b: BEGIN;
+step s1exec: SELECT * FROM partrem WHERE a <> 1 AND a <> (SELECT 3); <waiting ...>
+step s2remp: ALTER TABLE partrem DETACH PARTITION partrem2 CONCURRENTLY; <waiting ...>
+step s3unlock: SELECT pg_advisory_unlock(12543);
+pg_advisory_unlock
+
+t              
+step s1exec: <... completed>
+a              b              
+
+2              JKL            
+step s1c: COMMIT;
+step s2remp: <... completed>
+
+starting permutation: s3lock s1brr s1exec s2remp s3unlock s1c
+step s3lock: SELECT pg_advisory_lock(12543);
+pg_advisory_lock
+
+               
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1exec: SELECT * FROM partrem WHERE a <> 1 AND a <> (SELECT 3); <waiting ...>
+step s2remp: ALTER TABLE partrem DETACH PARTITION partrem2 CONCURRENTLY; <waiting ...>
+step s3unlock: SELECT pg_advisory_unlock(12543);
+pg_advisory_unlock
+
+t              
+step s1exec: <... completed>
+a              b              
+
+2              JKL            
+step s1c: COMMIT;
+step s2remp: <... completed>
+
+starting permutation: s3lock s1b s1exec2 s2remp s3unlock s1c
+step s3lock: SELECT pg_advisory_lock(12543);
+pg_advisory_lock
+
+               
+step s1b: BEGIN;
+step s1exec2: SELECT * FROM partrem WHERE a <> (SELECT 2); <waiting ...>
+step s2remp: ALTER TABLE partrem DETACH PARTITION partrem2 CONCURRENTLY; <waiting ...>
+step s3unlock: SELECT pg_advisory_unlock(12543);
+pg_advisory_unlock
+
+t              
+step s1exec2: <... completed>
+a              b              
+
+1              ABC            
+3              DEF            
+step s1c: COMMIT;
+step s2remp: <... completed>
+
+starting permutation: s3lock s1brr s1exec2 s2remp s3unlock s1c
+step s3lock: SELECT pg_advisory_lock(12543);
+pg_advisory_lock
+
+               
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1exec2: SELECT * FROM partrem WHERE a <> (SELECT 2); <waiting ...>
+step s2remp: ALTER TABLE partrem DETACH PARTITION partrem2 CONCURRENTLY; <waiting ...>
+step s3unlock: SELECT pg_advisory_unlock(12543);
+pg_advisory_unlock
+
+t              
+step s1exec2: <... completed>
+a              b              
+
+1              ABC            
+3              DEF            
+step s1c: COMMIT;
+step s2remp: <... completed>
diff --git a/src/test/modules/delay_execution/specs/partition-removal-1.spec b/src/test/modules/delay_execution/specs/partition-removal-1.spec
new file mode 100644
index 0000000000..e8e99f15bf
--- /dev/null
+++ b/src/test/modules/delay_execution/specs/partition-removal-1.spec
@@ -0,0 +1,45 @@
+# Test removal of a partition with less-than-exclusive locking.
+
+setup
+{
+  CREATE TABLE partrem (a int, b text) PARTITION BY LIST(a);
+  CREATE TABLE partrem1 PARTITION OF partrem FOR VALUES IN (1);
+  CREATE TABLE partrem2 PARTITION OF partrem FOR VALUES IN (2);
+  CREATE TABLE partrem3 PARTITION OF partrem FOR VALUES IN (3);
+  INSERT INTO partrem VALUES (1, 'ABC');
+  INSERT INTO partrem VALUES (2, 'JKL');
+  INSERT INTO partrem VALUES (3, 'DEF');
+}
+
+teardown
+{
+  DROP TABLE IF EXISTS partrem, partrem2;
+}
+
+# The SELECT will be planned with all three partitions shown above,
+# of which we expect partrem1 to be pruned at planning and partrem3 at
+# execution. Then we'll block, and by the time the query is actually
+# executed, detach of partrem2 is already underway; however we expect
+# its rows to still appear in the result.
+
+session "s1"
+setup		{ LOAD 'delay_execution';
+		  SET delay_execution.post_planning_lock_id = 12543; }
+step "s1b"	{ BEGIN; }
+step "s1brr"	{ BEGIN ISOLATION LEVEL REPEATABLE READ; }
+step "s1exec"	{ SELECT * FROM partrem WHERE a <> 1 AND a <> (SELECT 3); }
+step "s1exec2"	{ SELECT * FROM partrem WHERE a <> (SELECT 2); }
+step "s1c"	{ COMMIT; }
+
+session "s2"
+step "s2remp"	{ ALTER TABLE partrem DETACH PARTITION partrem2 CONCURRENTLY; }
+
+session "s3"
+step "s3lock"	{ SELECT pg_advisory_lock(12543); }
+step "s3unlock"	{ SELECT pg_advisory_unlock(12543); }
+
+permutation "s3lock" "s1b" "s1exec" "s2remp" "s3unlock" "s1c"
+permutation "s3lock" "s1brr" "s1exec" "s2remp" "s3unlock" "s1c"
+
+permutation "s3lock" "s1b" "s1exec2" "s2remp" "s3unlock" "s1c"
+permutation "s3lock" "s1brr" "s1exec2" "s2remp" "s3unlock" "s1c"
-- 
2.20.1

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