Here's a patch I propose to apply to fix this bug (See
<https://www.postgresql.org/message-id/flat/759e997e-e1ca-91cd-84db-f4ae963fada1%40dunslane.net#b1cf11c3eb1f450bed97c79ad473909f>)
cheers
andrew
--
Andrew Dunstan
EDB: https://www.enterprisedb.com
>From 5780fd5bf6878dcf8888d48289d80ca74c6d5b64 Mon Sep 17 00:00:00 2001
From: Andrew Dunstan <and...@dunslane.net>
Date: Thu, 17 Jun 2021 08:19:28 -0400
Subject: [PATCH] Don't set a fast default for anything but a plain table
MIME-Version: 1.0
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The fast default code added in Release 11 omitted to check that the
table a fast default was being added to was a plain table. Thus one
could be added to a foreign table, which predicably blows up. Here we
perform that check, and in addition if we encounter a missing value for
an attribute of something other than a plain table we ignore it.
Fixes bug #17056
Backpatch to release 11,
Reviewed by: Andres Freund and Álvaro Herrera
---
src/backend/catalog/heap.c | 10 +++++++++-
src/backend/commands/tablecmds.c | 5 +++--
src/backend/utils/cache/relcache.c | 9 +++++++++
src/test/regress/expected/fast_default.out | 19 +++++++++++++++++++
src/test/regress/sql/fast_default.sql | 14 ++++++++++++++
5 files changed, 54 insertions(+), 3 deletions(-)
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index afa830d924..1293dc04ca 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -2161,6 +2161,13 @@ SetAttrMissing(Oid relid, char *attname, char *value)
/* lock the table the attribute belongs to */
tablerel = table_open(relid, AccessExclusiveLock);
+ /* Don't do anything unless it's a plain table */
+ if (tablerel->rd_rel->relkind != RELKIND_RELATION)
+ {
+ table_close(tablerel, AccessExclusiveLock);
+ return;
+ }
+
/* Lock the attribute row and get the data */
attrrel = table_open(AttributeRelationId, RowExclusiveLock);
atttup = SearchSysCacheAttName(relid, attname);
@@ -2287,7 +2294,8 @@ StoreAttrDefault(Relation rel, AttrNumber attnum,
valuesAtt[Anum_pg_attribute_atthasdef - 1] = true;
replacesAtt[Anum_pg_attribute_atthasdef - 1] = true;
- if (add_column_mode && !attgenerated)
+ if (rel->rd_rel->relkind == RELKIND_RELATION && add_column_mode &&
+ !attgenerated)
{
expr2 = expression_planner(expr2);
estate = CreateExecutorState();
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 028e8ac46b..2eef07e452 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -12215,9 +12215,10 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
/*
* Here we go --- change the recorded column type and collation. (Note
* heapTup is a copy of the syscache entry, so okay to scribble on.) First
- * fix up the missing value if any.
+ * fix up the missing value if any. There shouldn't be any missing values
+ * for anything except plain tables, but if there are, ignore them.
*/
- if (attTup->atthasmissing)
+ if (rel->rd_rel->relkind == RELKIND_RELATION && attTup->atthasmissing)
{
Datum missingval;
bool missingNull;
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index fd05615e76..1d15671177 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -559,6 +559,15 @@ RelationBuildTupleDesc(Relation relation)
elog(ERROR, "invalid attribute number %d for relation \"%s\"",
attp->attnum, RelationGetRelationName(relation));
+ /*
+ * Fix atthasmissing flag - it's only for plain tables. Others
+ * should not have missing values set, but there may be some left from
+ * before when we placed that check, so this code defensively ignores
+ * such values.
+ */
+ if (relation->rd_rel->relkind != RELKIND_RELATION)
+ attp->atthasmissing = false;
+
memcpy(TupleDescAttr(relation->rd_att, attnum - 1),
attp,
ATTRIBUTE_FIXED_PART_SIZE);
diff --git a/src/test/regress/expected/fast_default.out b/src/test/regress/expected/fast_default.out
index 10bc5ff757..91f25717b5 100644
--- a/src/test/regress/expected/fast_default.out
+++ b/src/test/regress/expected/fast_default.out
@@ -797,7 +797,26 @@ SELECT * FROM t WHERE a IS NULL;
(1 row)
ROLLBACK;
+-- verify that a default set on a non-plain table doesn't set a missing
+-- value on the attribute
+CREATE FOREIGN DATA WRAPPER dummy;
+CREATE SERVER s0 FOREIGN DATA WRAPPER dummy;
+CREATE FOREIGN TABLE ft1 (c1 integer NOT NULL) SERVER s0;
+ALTER FOREIGN TABLE ft1 ADD COLUMN c8 integer DEFAULT 0;
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10);
+SELECT count(*)
+ FROM pg_attribute
+ WHERE attrelid = 'ft1'::regclass AND
+ (attmissingval IS NOT NULL OR atthasmissing);
+ count
+-------
+ 0
+(1 row)
+
-- cleanup
+DROP FOREIGN TABLE ft1;
+DROP SERVER s0;
+DROP FOREIGN DATA WRAPPER dummy;
DROP TABLE vtype;
DROP TABLE vtype2;
DROP TABLE follower;
diff --git a/src/test/regress/sql/fast_default.sql b/src/test/regress/sql/fast_default.sql
index 4589b9e58d..16a3b7ca51 100644
--- a/src/test/regress/sql/fast_default.sql
+++ b/src/test/regress/sql/fast_default.sql
@@ -524,8 +524,22 @@ SET LOCAL enable_seqscan = false;
SELECT * FROM t WHERE a IS NULL;
ROLLBACK;
+-- verify that a default set on a non-plain table doesn't set a missing
+-- value on the attribute
+CREATE FOREIGN DATA WRAPPER dummy;
+CREATE SERVER s0 FOREIGN DATA WRAPPER dummy;
+CREATE FOREIGN TABLE ft1 (c1 integer NOT NULL) SERVER s0;
+ALTER FOREIGN TABLE ft1 ADD COLUMN c8 integer DEFAULT 0;
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10);
+SELECT count(*)
+ FROM pg_attribute
+ WHERE attrelid = 'ft1'::regclass AND
+ (attmissingval IS NOT NULL OR atthasmissing);
-- cleanup
+DROP FOREIGN TABLE ft1;
+DROP SERVER s0;
+DROP FOREIGN DATA WRAPPER dummy;
DROP TABLE vtype;
DROP TABLE vtype2;
DROP TABLE follower;
--
2.25.4
