From fe9e658f4d7fbc12d2b6a74c4ee90c73e53d68ef Mon Sep 17 00:00:00 2001 From: Dean Rasheed Date: Mon, 30 Jan 2023 10:04:57 +0000 Subject: [PATCH] Ensure that MERGE recomputes GENERATED expressions properly. This fixes a bug that, under some circumstances, would cause MERGE to fail to properly recompute expressions for GENERATED STORED columns. Formerly, ExecInitModifyTable() did not call ExecInitStoredGenerated() for a MERGE command, which meant that the generated expressions information was not computed until later, when the first merge action was executed. However, if the first merge action to execute was an UPDATE, then ExecInitStoredGenerated() could decide to skip some some generated columns, if the columns on which they depended were not updated, which was a problem if the MERGE also contained an INSERT action, for which no generated columns should be skipped. So fix by having ExecInitModifyTable() call ExecInitStoredGenerated() for MERGE, and assume that it isn't safe to skip any generated columns in a MERGE. Possibly that could be relaxed, by allowing some generated columns to be skipped for a MERGE without an INSERT action, but it's not clear that it's worth the effort. Noticed while investigating bug #17759. Back-patch to v15, where MERGE was added. Dean Rasheed, reviewed by Tom Lane. Discussion: https://postgr.es/m/17759-e76d9bece1b5421c%40postgresql.org https://postgr.es/m/CAEZATCXb_ezoMCcL0tzKwRGA1x0oeE%3DawTaysRfTPq%2B3wNJn8g%40mail.gmail.com --- src/backend/executor/nodeModifyTable.c | 4 ++-- src/test/regress/expected/generated.out | 20 ++++++++++++++++++++ src/test/regress/sql/generated.sql | 15 +++++++++++++++ 3 files changed, 37 insertions(+), 2 deletions(-) diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c index f419c47065a..1ac65172e44 100644 --- a/src/backend/executor/nodeModifyTable.c +++ b/src/backend/executor/nodeModifyTable.c @@ -4141,12 +4141,12 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags) } /* - * For INSERT and UPDATE, prepare to evaluate any generated columns. + * For INSERT/UPDATE/MERGE, prepare to evaluate any generated columns. * We must do this now, even if we never insert or update any rows, * because we have to fill resultRelInfo->ri_extraUpdatedCols for * possible use by the trigger machinery. */ - if (operation == CMD_INSERT || operation == CMD_UPDATE) + if (operation == CMD_INSERT || operation == CMD_UPDATE || operation == CMD_MERGE) ExecInitStoredGenerated(resultRelInfo, estate, operation); } diff --git a/src/test/regress/expected/generated.out b/src/test/regress/expected/generated.out index 9867748c0f5..11940c851f2 100644 --- a/src/test/regress/expected/generated.out +++ b/src/test/regress/expected/generated.out @@ -192,6 +192,26 @@ SELECT * FROM gtest1 ORDER BY a; 3 | 6 (1 row) +-- test MERGE +CREATE TABLE gtestm ( + id int PRIMARY KEY, + f1 int, + f2 int, + f3 int GENERATED ALWAYS AS (f1 * 2) STORED, + f4 int GENERATED ALWAYS AS (f2 * 2) STORED +); +INSERT INTO gtestm VALUES (1, 5, 100); +MERGE INTO gtestm t USING (VALUES (1, 10), (2, 20)) v(id, f1) ON t.id = v.id + WHEN MATCHED THEN UPDATE SET f1 = v.f1 + WHEN NOT MATCHED THEN INSERT VALUES (v.id, v.f1, 200); +SELECT * FROM gtestm ORDER BY id; + id | f1 | f2 | f3 | f4 +----+----+-----+----+----- + 1 | 10 | 100 | 20 | 200 + 2 | 20 | 200 | 40 | 400 +(2 rows) + +DROP TABLE gtestm; -- views CREATE VIEW gtest1v AS SELECT * FROM gtest1; SELECT * FROM gtest1v; diff --git a/src/test/regress/sql/generated.sql b/src/test/regress/sql/generated.sql index 92d373b6384..87ec8421162 100644 --- a/src/test/regress/sql/generated.sql +++ b/src/test/regress/sql/generated.sql @@ -81,6 +81,21 @@ SELECT * FROM gtest1 ORDER BY a; DELETE FROM gtest1 WHERE b = 2; SELECT * FROM gtest1 ORDER BY a; +-- test MERGE +CREATE TABLE gtestm ( + id int PRIMARY KEY, + f1 int, + f2 int, + f3 int GENERATED ALWAYS AS (f1 * 2) STORED, + f4 int GENERATED ALWAYS AS (f2 * 2) STORED +); +INSERT INTO gtestm VALUES (1, 5, 100); +MERGE INTO gtestm t USING (VALUES (1, 10), (2, 20)) v(id, f1) ON t.id = v.id + WHEN MATCHED THEN UPDATE SET f1 = v.f1 + WHEN NOT MATCHED THEN INSERT VALUES (v.id, v.f1, 200); +SELECT * FROM gtestm ORDER BY id; +DROP TABLE gtestm; + -- views CREATE VIEW gtest1v AS SELECT * FROM gtest1; SELECT * FROM gtest1v;