From cb848422ab67077567fa7ee3a3b2f2d9367a8a65 Mon Sep 17 00:00:00 2001 From: Dean Rasheed Date: Sat, 19 Sep 2026 09:32:21 +0100 Subject: [PATCH v3] Fix concurrent delete handling in MERGE ... WHEN NOT MATCHED BY SOURCE. When executing a WHEN NOT MATCHED BY SOURCE action in MERGE, if the tuple from the target table was concurrently deleted, the retry code would incorrectly execute any WHEN NOT MATCHED BY TARGET action for the row instead, giving incorrect results. Fix in ExecMergeMatched() -- when handling a TM_Deleted failure status, it should only set *matched to false (telling the caller to execute any WHEN NOT MATCHED BY TARGET actions) if the failed action was a WHEN MATCHED action. For a failed WHEN NOT MATCHED BY SOURCE action, the source tuple did not exist, and the target tuple has just been deleted, so there is nothing to do. Back-patch to v17, where support for WHEN NOT MATCHED BY SOURCE actions was introduced. Reported-by: Jeff Davis Author: Tender Wang Reviewed-by: Dean Rasheed Discussion: https://postgr.es/m/ccdab5ba02c65af195b5a6d2d744a01d9de47cd3.camel@j-davis.com Backpatch-through: 17 --- src/backend/executor/nodeModifyTable.c | 35 ++-- src/test/isolation/expected/merge-delete.out | 158 +++++++++++++++++++ src/test/isolation/specs/merge-delete.spec | 37 +++++ 3 files changed, 220 insertions(+), 10 deletions(-) diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c index 2632431ea05..558ceece9bb 100644 --- a/src/backend/executor/nodeModifyTable.c +++ b/src/backend/executor/nodeModifyTable.c @@ -3261,10 +3261,11 @@ ExecMerge(ModifyTableContext *context, ResultRelInfo *resultRelInfo, * Otherwise, we execute the qualifying action and return its RETURNING * result, if any, or NULL. * - * On entry, "*matched" is assumed to be true. If a concurrent update or - * delete is detected that causes the join quals to no longer pass, we set it - * to false, indicating that the caller should process any NOT MATCHED [BY - * TARGET] actions. + * On entry, "*matched" is assumed to be true. If the join quals originally + * passed (MATCHED case) and a concurrent update or delete is detected that + * causes the join quals to no longer pass, we set "*matched" to false, + * indicating that the caller should process any NOT MATCHED [BY TARGET] + * actions. * * After a concurrent update, we restart from the first action to look for a * new qualifying action to execute. If the join quals originally passed, and @@ -3561,10 +3562,16 @@ lmerge_matched: errmsg("could not serialize access due to concurrent delete"))); /* - * If the tuple was already deleted, set matched to false to - * let caller handle it under NOT MATCHED [BY TARGET] clauses. + * The target tuple was concurrently deleted by some other + * transaction. If this was a MATCHED action, the source row + * still exists, so set *matched to false, to let the caller + * handle it using any NOT MATCHED [BY TARGET] actions. + * Otherwise, for a NOT MATCHED BY SOURCE action, neither the + * source row nor the target row now exists, so there is no + * futher action to execute. */ - *matched = false; + if (relaction->mas_action->matchKind == MERGE_WHEN_MATCHED) + *matched = false; goto out; case TM_Updated: @@ -3717,10 +3724,18 @@ lmerge_matched: case TM_Deleted: /* - * tuple already deleted; tell caller to run NOT - * MATCHED [BY TARGET] actions + * The target tuple was concurrently deleted by + * some other transaction. If this was a MATCHED + * action, the source row still exists, so set + * *matched to false, to let the caller handle it + * using any NOT MATCHED [BY TARGET] actions. + * Otherwise, for a NOT MATCHED BY SOURCE action, + * neither the source row nor the target row now + * exists, so there is no futher action to + * execute. */ - *matched = false; + if (was_matched) + *matched = false; goto out; case TM_SelfModified: diff --git a/src/test/isolation/expected/merge-delete.out b/src/test/isolation/expected/merge-delete.out index 897b9351355..c0e3b2b5e7f 100644 --- a/src/test/isolation/expected/merge-delete.out +++ b/src/test/isolation/expected/merge-delete.out @@ -234,3 +234,161 @@ key|val (1 row) step c2: COMMIT; + +starting permutation: delete merge_wnmbs_src2 c1 select2 c2 +step delete: DELETE FROM target t WHERE t.key = 1; +step merge_wnmbs_src2: + MERGE INTO target t + USING (SELECT 2 AS key, 'merge2' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; + +step c1: COMMIT; +step merge_wnmbs_src2: <... completed> +merge_action|key|val +------------+---+------ +INSERT | 2|merge2 +(1 row) + +step select2: SELECT * FROM target; +key|val +---+------ + 2|merge2 +(1 row) + +step c2: COMMIT; + +starting permutation: delete_pa merge_wnmbs_src2_pa c1 select2_pa c2 +step delete_pa: DELETE FROM target_pa t WHERE t.key = 1; +step merge_wnmbs_src2_pa: + MERGE INTO target_pa t + USING (SELECT 2 AS key, 'merge2_pa' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; + +step c1: COMMIT; +step merge_wnmbs_src2_pa: <... completed> +merge_action|key|val +------------+---+--------- +INSERT | 2|merge2_pa +(1 row) + +step select2_pa: SELECT * FROM target_pa; +key|val +---+--------- + 2|merge2_pa +(1 row) + +step c2: COMMIT; + +starting permutation: delete_tg merge_wnmbs_src2_tg c1 select2_tg c2 +s1: NOTICE: Delete: (1,setup1) +step delete_tg: DELETE FROM target_tg t WHERE t.key = 1; +step merge_wnmbs_src2_tg: + MERGE INTO target_tg t + USING (SELECT 2 AS key, 'merge2_tg' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; + +step c1: COMMIT; +s2: NOTICE: Insert: (2,merge2_tg) +step merge_wnmbs_src2_tg: <... completed> +merge_action|key|val +------------+---+--------- +INSERT | 2|merge2_tg +(1 row) + +step select2_tg: SELECT * FROM target_tg; +key|val +---+--------- + 2|merge2_tg +(1 row) + +step c2: COMMIT; + +starting permutation: update delete merge_wnmbs_src2 c1 select2 c2 +step update: UPDATE target t SET val = t.val || ' update1' WHERE t.key = 1; +step delete: DELETE FROM target t WHERE t.key = 1; +step merge_wnmbs_src2: + MERGE INTO target t + USING (SELECT 2 AS key, 'merge2' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; + +step c1: COMMIT; +step merge_wnmbs_src2: <... completed> +merge_action|key|val +------------+---+------ +INSERT | 2|merge2 +(1 row) + +step select2: SELECT * FROM target; +key|val +---+------ + 2|merge2 +(1 row) + +step c2: COMMIT; + +starting permutation: update_pa delete_pa merge_wnmbs_src2_pa c1 select2_pa c2 +step update_pa: UPDATE target_pa t SET val = t.val || ' update1' WHERE t.key = 1; +step delete_pa: DELETE FROM target_pa t WHERE t.key = 1; +step merge_wnmbs_src2_pa: + MERGE INTO target_pa t + USING (SELECT 2 AS key, 'merge2_pa' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; + +step c1: COMMIT; +step merge_wnmbs_src2_pa: <... completed> +merge_action|key|val +------------+---+--------- +INSERT | 2|merge2_pa +(1 row) + +step select2_pa: SELECT * FROM target_pa; +key|val +---+--------- + 2|merge2_pa +(1 row) + +step c2: COMMIT; + +starting permutation: update_tg delete_tg merge_wnmbs_src2_tg c1 select2_tg c2 +s1: NOTICE: Update: (1,setup1) -> (1,"setup1 update1") +step update_tg: UPDATE target_tg t SET val = t.val || ' update1' WHERE t.key = 1; +s1: NOTICE: Delete: (1,"setup1 update1") +step delete_tg: DELETE FROM target_tg t WHERE t.key = 1; +step merge_wnmbs_src2_tg: + MERGE INTO target_tg t + USING (SELECT 2 AS key, 'merge2_tg' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; + +step c1: COMMIT; +s2: NOTICE: Insert: (2,merge2_tg) +step merge_wnmbs_src2_tg: <... completed> +merge_action|key|val +------------+---+--------- +INSERT | 2|merge2_tg +(1 row) + +step select2_tg: SELECT * FROM target_tg; +key|val +---+--------- + 2|merge2_tg +(1 row) + +step c2: COMMIT; diff --git a/src/test/isolation/specs/merge-delete.spec b/src/test/isolation/specs/merge-delete.spec index ba5f70e53dc..833ce1fea65 100644 --- a/src/test/isolation/specs/merge-delete.spec +++ b/src/test/isolation/specs/merge-delete.spec @@ -50,6 +50,9 @@ setup step "delete" { DELETE FROM target t WHERE t.key = 1; } step "delete_pa" { DELETE FROM target_pa t WHERE t.key = 1; } step "delete_tg" { DELETE FROM target_tg t WHERE t.key = 1; } +step "update" { UPDATE target t SET val = t.val || ' update1' WHERE t.key = 1; } +step "update_pa" { UPDATE target_pa t SET val = t.val || ' update1' WHERE t.key = 1; } +step "update_tg" { UPDATE target_tg t SET val = t.val || ' update1' WHERE t.key = 1; } step "c1" { COMMIT; } session "s2" @@ -65,6 +68,30 @@ step "merge2_pa" { MERGE INTO target_pa t USING (SELECT 1 as key, 'merge2_pa' as step "merge2_tg" { MERGE INTO target_tg t USING (SELECT 1 as key, 'merge2_tg' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set key = t.key + 1, val = t.val || ' updated by ' || s.val; } step "merge_delete2" { MERGE INTO target t USING (SELECT 1 as key, 'merge_delete2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN DELETE; } step "merge_delete2_tg" { MERGE INTO target_tg t USING (SELECT 1 as key, 'merge_delete2_tg' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN DELETE; } +step "merge_wnmbs_src2" { + MERGE INTO target t + USING (SELECT 2 AS key, 'merge2' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; +} +step "merge_wnmbs_src2_pa" { + MERGE INTO target_pa t + USING (SELECT 2 AS key, 'merge2_pa' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; +} +step "merge_wnmbs_src2_tg" { + MERGE INTO target_tg t + USING (SELECT 2 AS key, 'merge2_tg' AS val) s ON t.key = s.key + WHEN MATCHED THEN UPDATE SET key = t.key + 1, val = t.val || ' match updated by ' || s.val + WHEN NOT MATCHED BY SOURCE THEN UPDATE SET key = t.key + 1, val = t.val || ' not matched by source' + WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) + RETURNING merge_action(), t.*; +} step "select2" { SELECT * FROM target; } step "select2_pa" { SELECT * FROM target_pa; } step "select2_tg" { SELECT * FROM target_tg; } @@ -94,3 +121,13 @@ permutation "delete_pa" "merge2_pa" "c1" "select2_pa" "c2" permutation "delete_tg" "merge2_tg" "c1" "select2_tg" "c2" permutation "delete" "merge_delete2" "c1" "select2" "c2" permutation "delete_tg" "merge_delete2_tg" "c1" "select2_tg" "c2" + +# Concurrent DELETE vs MERGE ... WHEN NOT MATCHED BY SOURCE +permutation "delete" "merge_wnmbs_src2" "c1" "select2" "c2" +permutation "delete_pa" "merge_wnmbs_src2_pa" "c1" "select2_pa" "c2" +permutation "delete_tg" "merge_wnmbs_src2_tg" "c1" "select2_tg" "c2" + +# Concurrent UPDATE then DELETE vs MERGE ... WHEN NOT MATCHED BY SOURCE +permutation "update" "delete" "merge_wnmbs_src2" "c1" "select2" "c2" +permutation "update_pa" "delete_pa" "merge_wnmbs_src2_pa" "c1" "select2_pa" "c2" +permutation "update_tg" "delete_tg" "merge_wnmbs_src2_tg" "c1" "select2_tg" "c2" -- 2.51.0