From 18bdeab3d74e539835d59c9a86da8f4ccf2243be Mon Sep 17 00:00:00 2001 From: Fujii Masao Date: Thu, 3 Apr 2025 18:41:44 +0900 Subject: [PATCH v4] Allow "COPY table TO" command to copy rows from materialized views. Previously, "COPY table TO" command worked only with plain tables and did not support materialized views, even when they were populated and had physical storage. To copy rows from materialized views, "COPY (query) TO" command had to be used, instead. This commit extends "COPY table TO" to support populated materialized views directly, improving usability and performance, as "COPY table TO" is generally faster than "COPY (query) TO". Note that copying from unpopulated materialized views will still result in an error. Author: jian he Reviewed-by: Kirill Reshke Reviewed-by: David G. Johnston Reviewed-by: Vignesh C Reviewed-by: Fujii Masao Discussion: https://postgr.es/m/CACJufxHVxnyRYy67hiPePNCPwVBMzhTQ6FaL9_Te5On9udG=yg@mail.gmail.com --- doc/src/sgml/ref/copy.sgml | 20 ++++++++++---------- src/backend/commands/copyto.c | 13 ++++++++----- src/test/regress/expected/copy.out | 12 ++++++++++++ src/test/regress/sql/copy.sql | 9 +++++++++ 4 files changed, 39 insertions(+), 15 deletions(-) diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml index df093da97c5..d6859276bed 100644 --- a/doc/src/sgml/ref/copy.sgml +++ b/doc/src/sgml/ref/copy.sgml @@ -520,16 +520,16 @@ COPY count Notes - COPY TO can be used only with plain - tables, not views, and does not copy rows from child tables - or child partitions. For example, COPY table TO copies - the same rows as SELECT * FROM ONLY table. - The syntax COPY (SELECT * FROM table) TO ... can be used to - dump all of the rows in an inheritance hierarchy, partitioned table, - or view. + COPY TO can be used with plain + tables and populated materialized views. + For example, + COPY table + TO copies the same rows as + SELECT * FROM ONLY table. + However it doesn't directly support other relation types, + such as partitioned tables, inheritance child tables, or views. + To copy all rows from such relations, use COPY (SELECT * FROM + table) TO. diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c index 84a3f3879a8..f87e405351d 100644 --- a/src/backend/commands/copyto.c +++ b/src/backend/commands/copyto.c @@ -653,11 +653,14 @@ BeginCopyTo(ParseState *pstate, RelationGetRelationName(rel)), errhint("Try the COPY (SELECT ...) TO variant."))); else if (rel->rd_rel->relkind == RELKIND_MATVIEW) - ereport(ERROR, - (errcode(ERRCODE_WRONG_OBJECT_TYPE), - errmsg("cannot copy from materialized view \"%s\"", - RelationGetRelationName(rel)), - errhint("Try the COPY (SELECT ...) TO variant."))); + { + if (!RelationIsPopulated(rel)) + ereport(ERROR, + errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("cannot copy from unpopulated materialized view \"%s\"", + RelationGetRelationName(rel)), + errhint("Use the REFRESH MATERIALIZED VIEW command.")); + } else if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), diff --git a/src/test/regress/expected/copy.out b/src/test/regress/expected/copy.out index 06bae8c61ae..8d5a06563c4 100644 --- a/src/test/regress/expected/copy.out +++ b/src/test/regress/expected/copy.out @@ -338,3 +338,15 @@ create foreign table copytest_foreign_table (a int) server copytest_server; copy copytest_foreign_table from stdin (freeze); ERROR: cannot perform COPY FREEZE on a foreign table rollback; +-- Tests for COPY TO with materialized views. +-- COPY TO should fail for an unpopulated materialized view +-- but succeed for a populated one. +CREATE MATERIALIZED VIEW copytest_mv AS SELECT 1 AS id WITH NO DATA; +COPY copytest_mv(id) TO stdout WITH (header); +ERROR: cannot copy from unpopulated materialized view "copytest_mv" +HINT: Use the REFRESH MATERIALIZED VIEW command. +REFRESH MATERIALIZED VIEW copytest_mv; +COPY copytest_mv(id) TO stdout WITH (header); +id +1 +DROP MATERIALIZED VIEW copytest_mv; diff --git a/src/test/regress/sql/copy.sql b/src/test/regress/sql/copy.sql index 3009bdfdf89..f0b88a23db8 100644 --- a/src/test/regress/sql/copy.sql +++ b/src/test/regress/sql/copy.sql @@ -366,3 +366,12 @@ copy copytest_foreign_table from stdin (freeze); 1 \. rollback; + +-- Tests for COPY TO with materialized views. +-- COPY TO should fail for an unpopulated materialized view +-- but succeed for a populated one. +CREATE MATERIALIZED VIEW copytest_mv AS SELECT 1 AS id WITH NO DATA; +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; -- 2.48.1