hi. In the V10 patch, there will be some regression if the partition column ordering is different from the root partitioned table.
because in V10 CopyThisRelTo
+ while (table_scan_getnextslot(scandesc, ForwardScanDirection, slot))
+ {
+ if (map != NULL)
+ {
+ original_slot = slot;
+ root_slot = MakeSingleTupleTableSlot(rootdesc, &TTSOpsBufferHeapTuple);
+ slot = execute_attr_map_slot(map, slot, root_slot);
+ }
+ else
+ slot_getallattrs(slot);
+
+ if (original_slot != NULL)
+ ExecDropSingleTupleTableSlot(original_slot);
+}
as you can see, for each slot in the partition, i called
MakeSingleTupleTableSlot to get the dumpy root_slot
and ExecDropSingleTupleTableSlot too.
that will cause overhead.
we can call produce root_slot before the main while loop.
like the following:
+ if (root_rel != NULL)
+ {
+ rootdesc = RelationGetDescr(root_rel);
+ root_slot = table_slot_create(root_rel, NULL);
+ map = build_attrmap_by_name_if_req(rootdesc, tupdesc, false);
+ }
....
+ while (table_scan_getnextslot(scandesc, ForwardScanDirection, slot))
+ {
+ TupleTableSlot *copyslot;
+ if (map != NULL)
+ copyslot = execute_attr_map_slot(map, slot, root_slot);
+ else
+ {
+ slot_getallattrs(slot);
+ copyslot = slot;
+ }
+
please check CopyThisRelTo in v11. so, with v11, there is no
regression for case when
partition column ordering differs from partitioned.
I have tested 30 partitions, 10 columns, all the column ordering
is different with the root partitioned table.
copy pp to '/tmp/2.txt'
is still faster than
copy (select * from pp) to '/tmp/1.txt';
(359.463 ms versus 376.371 ms)
I am using -Dbuildtype=release
PostgreSQL 18beta1_release_build on x86_64-linux, compiled by gcc-14.1.0, 64-bit
you may see the attached test file.
copy_par_regress_test-7.sql
Description: application/sql
From fca7b87718264cb5ea52f3b4462f4d6e52d58cdc Mon Sep 17 00:00:00 2001 From: jian he <jian.universal...@gmail.com> Date: Thu, 5 Jun 2025 08:44:13 +0800 Subject: [PATCH v11 1/1] support COPY partitioned_table TO this is for implementatoin of ``COPY (partitioned_table) TO``. it will be faster than ``COPY (select * from partitioned_table) TO``. reivewed by: vignesh C <vignes...@gmail.com> reivewed by: David Rowley <dgrowle...@gmail.com> reivewed by: Melih Mutlu <m.melihmu...@gmail.com> reivewed by: Kirill Reshke <reshkekir...@gmail.com> discussion: https://postgr.es/m/CACJufxEZt+G19Ors3bQUq-42-61__C=y5k2wk=sHEFRusu7=i...@mail.gmail.com commitfest entry: https://commitfest.postgresql.org/patch/5467/ --- doc/src/sgml/ref/copy.sgml | 6 +- src/backend/commands/copyto.c | 146 +++++++++++++++++++++++------ src/test/regress/expected/copy.out | 18 ++++ src/test/regress/sql/copy.sql | 15 +++ 4 files changed, 153 insertions(+), 32 deletions(-) diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml index 8433344e5b6..d750a2fef7c 100644 --- a/doc/src/sgml/ref/copy.sgml +++ b/doc/src/sgml/ref/copy.sgml @@ -521,13 +521,13 @@ COPY <replaceable class="parameter">count</replaceable> <para> <command>COPY TO</command> can be used with plain - tables and populated materialized views. - For example, + tables, populated materialized views and partitioned tables. + For example, if <replaceable class="parameter">table</replaceable> is not partitioned table, <literal>COPY <replaceable class="parameter">table</replaceable> TO</literal> copies the same rows as <literal>SELECT * FROM ONLY <replaceable class="parameter">table</replaceable></literal>. However it doesn't directly support other relation types, - such as partitioned tables, inheritance child tables, or views. + such as inheritance child tables, or views. To copy all rows from such relations, use <literal>COPY (SELECT * FROM <replaceable class="parameter">table</replaceable>) TO</literal>. </para> diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c index ea6f18f2c80..a718ad02960 100644 --- a/src/backend/commands/copyto.c +++ b/src/backend/commands/copyto.c @@ -19,6 +19,8 @@ #include <sys/stat.h> #include "access/tableam.h" +#include "access/table.h" +#include "catalog/pg_inherits.h" #include "commands/copyapi.h" #include "commands/progress.h" #include "executor/execdesc.h" @@ -82,6 +84,7 @@ typedef struct CopyToStateData List *attnumlist; /* integer list of attnums to copy */ char *filename; /* filename, or NULL for STDOUT */ bool is_program; /* is 'filename' a program to popen? */ + List *partitions; /* oid list of partition oid for copy to */ copy_data_dest_cb data_dest_cb; /* function for writing data */ CopyFormatOptions opts; @@ -116,6 +119,8 @@ static void CopyOneRowTo(CopyToState cstate, TupleTableSlot *slot); static void CopyAttributeOutText(CopyToState cstate, const char *string); static void CopyAttributeOutCSV(CopyToState cstate, const char *string, bool use_quote); +static void CopyThisRelTo(CopyToState cstate, Relation rel, + Relation root_rel, uint64 *processed); /* built-in format-specific routines */ static void CopyToTextLikeStart(CopyToState cstate, TupleDesc tupDesc); @@ -643,6 +648,8 @@ BeginCopyTo(ParseState *pstate, PROGRESS_COPY_COMMAND_TO, 0 }; + List *children = NIL; + List *scan_oids = NIL; if (rel != NULL && rel->rd_rel->relkind != RELKIND_RELATION) { @@ -673,11 +680,35 @@ BeginCopyTo(ParseState *pstate, errmsg("cannot copy from sequence \"%s\"", RelationGetRelationName(rel)))); else if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE) - ereport(ERROR, - (errcode(ERRCODE_WRONG_OBJECT_TYPE), - errmsg("cannot copy from partitioned table \"%s\"", - RelationGetRelationName(rel)), - errhint("Try the COPY (SELECT ...) TO variant."))); + { + children = find_all_inheritors(RelationGetRelid(rel), + AccessShareLock, + NULL); + + foreach_oid(childreloid, children) + { + char relkind = get_rel_relkind(childreloid); + + if (relkind == RELKIND_FOREIGN_TABLE) + { + char *relation_name; + + relation_name = get_rel_name(childreloid); + ereport(ERROR, + errcode(ERRCODE_WRONG_OBJECT_TYPE), + errmsg("cannot copy from foreign table \"%s\"", relation_name), + errdetail("Partition \"%s\" is a foreign table in the partitioned table \"%s.%s\"", + relation_name, RelationGetRelationName(rel), + get_namespace_name(rel->rd_rel->relnamespace)), + errhint("Try the COPY (SELECT ...) TO variant.")); + } + + if (RELKIND_HAS_PARTITIONS(relkind)) + continue; + + scan_oids = lappend_oid(scan_oids, childreloid); + } + } else ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), @@ -713,6 +744,7 @@ BeginCopyTo(ParseState *pstate, cstate->rel = rel; tupDesc = RelationGetDescr(cstate->rel); + cstate->partitions = list_copy(scan_oids); } else { @@ -722,6 +754,7 @@ BeginCopyTo(ParseState *pstate, DestReceiver *dest; cstate->rel = NULL; + cstate->partitions = NIL; /* * Run parse analysis and rewrite. Note this also acquires sufficient @@ -1030,7 +1063,7 @@ DoCopyTo(CopyToState cstate) TupleDesc tupDesc; int num_phys_attrs; ListCell *cur; - uint64 processed; + uint64 processed = 0; if (fe_copy) SendCopyBegin(cstate); @@ -1068,36 +1101,25 @@ DoCopyTo(CopyToState cstate) cstate->routine->CopyToStart(cstate, tupDesc); - if (cstate->rel) + /* + * if COPY TO source table is a partitioned table, then open each + * partition and process each individual partition. + */ + if (cstate->rel && cstate->rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE) { - TupleTableSlot *slot; - TableScanDesc scandesc; - - scandesc = table_beginscan(cstate->rel, GetActiveSnapshot(), 0, NULL); - slot = table_slot_create(cstate->rel, NULL); - - processed = 0; - while (table_scan_getnextslot(scandesc, ForwardScanDirection, slot)) + foreach_oid(scan_oid, cstate->partitions) { - CHECK_FOR_INTERRUPTS(); + Relation scan_rel; - /* Deconstruct the tuple ... */ - slot_getallattrs(slot); + scan_rel = table_open(scan_oid, AccessShareLock); - /* Format and send the data */ - CopyOneRowTo(cstate, slot); + CopyThisRelTo(cstate, scan_rel, cstate->rel, &processed); - /* - * Increment the number of processed tuples, and report the - * progress. - */ - pgstat_progress_update_param(PROGRESS_COPY_TUPLES_PROCESSED, - ++processed); + table_close(scan_rel, AccessShareLock); } - - ExecDropSingleTupleTableSlot(slot); - table_endscan(scandesc); } + else if (cstate->rel) + CopyThisRelTo(cstate, cstate->rel, NULL, &processed); else { /* run the plan --- the dest receiver will send tuples */ @@ -1115,6 +1137,72 @@ DoCopyTo(CopyToState cstate) return processed; } +/* + * rel: the relation from which the actual data will be copied. + * root_rel: if not NULL, it indicates that we are copying partitioned relation + * data to the destination, and "rel" is the partition of "root_rel". + * processed: number of tuples processed. +*/ +static void +CopyThisRelTo(CopyToState cstate, Relation rel, Relation root_rel, + uint64 *processed) +{ + TupleTableSlot *slot; + TableScanDesc scandesc; + AttrMap *map = NULL; + TupleTableSlot *root_slot = NULL; + TupleDesc tupdesc; + TupleDesc rootdesc; + + tupdesc = RelationGetDescr(rel); + scandesc = table_beginscan(rel, GetActiveSnapshot(), 0, NULL); + slot = table_slot_create(rel, NULL); + + /* + * A partition's rowtype might differ from the root table's. Since we are + * export partitioned table data here, we must convert it back to the root + * table's rowtype. + */ + if (root_rel != NULL) + { + rootdesc = RelationGetDescr(root_rel); + root_slot = table_slot_create(root_rel, NULL); + map = build_attrmap_by_name_if_req(rootdesc, tupdesc, false); + } + + while (table_scan_getnextslot(scandesc, ForwardScanDirection, slot)) + { + TupleTableSlot *copyslot; + + CHECK_FOR_INTERRUPTS(); + + /* Deconstruct the tuple ... */ + if (map != NULL) + copyslot = execute_attr_map_slot(map, slot, root_slot); + else + { + slot_getallattrs(slot); + copyslot = slot; + } + + /* Format and send the data */ + CopyOneRowTo(cstate, copyslot); + + /* + * Increment the number of processed tuples, and report the + * progress. + */ + pgstat_progress_update_param(PROGRESS_COPY_TUPLES_PROCESSED, + ++(*processed)); + } + + ExecDropSingleTupleTableSlot(slot); + + if (root_slot != NULL) + ExecDropSingleTupleTableSlot(root_slot); + table_endscan(scandesc); +} + /* * Emit one row during DoCopyTo(). */ diff --git a/src/test/regress/expected/copy.out b/src/test/regress/expected/copy.out index 8d5a06563c4..05e5649c1bc 100644 --- a/src/test/regress/expected/copy.out +++ b/src/test/regress/expected/copy.out @@ -350,3 +350,21 @@ COPY copytest_mv(id) TO stdout WITH (header); id 1 DROP MATERIALIZED VIEW copytest_mv; +-- Tests for COPY TO with partitioned tables. +CREATE TABLE pp (id int,val int) PARTITION BY RANGE (id); +CREATE TABLE pp_1 (val int, id int) PARTITION BY RANGE (id); +CREATE TABLE pp_2 (val int, id int) PARTITION BY RANGE (id); +ALTER TABLE pp ATTACH PARTITION pp_1 FOR VALUES FROM (1) TO (5); +ALTER TABLE pp ATTACH PARTITION pp_2 FOR VALUES FROM (5) TO (10); +CREATE TABLE pp_15 PARTITION OF pp_1 FOR VALUES FROM (1) TO (5); +CREATE TABLE pp_510 PARTITION OF pp_2 FOR VALUES FROM (5) TO (10); +INSERT INTO pp SELECT g, 10 + g FROM generate_series(1,6) g; +COPY pp TO stdout(header); +id val +1 11 +2 12 +3 13 +4 14 +5 15 +6 16 +DROP TABLE PP; diff --git a/src/test/regress/sql/copy.sql b/src/test/regress/sql/copy.sql index f0b88a23db8..fd2627deefa 100644 --- a/src/test/regress/sql/copy.sql +++ b/src/test/regress/sql/copy.sql @@ -375,3 +375,18 @@ COPY copytest_mv(id) TO stdout WITH (header); REFRESH MATERIALIZED VIEW copytest_mv; COPY copytest_mv(id) TO stdout WITH (header); DROP MATERIALIZED VIEW copytest_mv; + +-- Tests for COPY TO with partitioned tables. +CREATE TABLE pp (id int,val int) PARTITION BY RANGE (id); +CREATE TABLE pp_1 (val int, id int) PARTITION BY RANGE (id); +CREATE TABLE pp_2 (val int, id int) PARTITION BY RANGE (id); +ALTER TABLE pp ATTACH PARTITION pp_1 FOR VALUES FROM (1) TO (5); +ALTER TABLE pp ATTACH PARTITION pp_2 FOR VALUES FROM (5) TO (10); + +CREATE TABLE pp_15 PARTITION OF pp_1 FOR VALUES FROM (1) TO (5); +CREATE TABLE pp_510 PARTITION OF pp_2 FOR VALUES FROM (5) TO (10); + +INSERT INTO pp SELECT g, 10 + g FROM generate_series(1,6) g; + +COPY pp TO stdout(header); +DROP TABLE PP; \ No newline at end of file -- 2.34.1
