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Commit8c67d29

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Relax overly strict assertion
Ever since its birth, ReorderBufferBuildTupleCidHash() has contained anassertion that a catalog tuple cannot change Cmax after acquiring one. Butthat's wrong: if a subtransaction executes DDL that affects that catalogtuple, and later aborts and another DDL affects the same tuple, it willchange Cmax. Relax the assertion to merely verify that the Cmax remainsvalid and monotonically increasing, instead.Add a test that tickles the relevant code.Diagnosed by, and initial patch submitted by: Arseny SherCo-authored-by: Arseny SherDiscussion:https://postgr.es/m/874l9p8hyw.fsf@ars-thinkpad
1 parentd357a16 commit8c67d29

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3 files changed

+40
-5
lines changed

3 files changed

+40
-5
lines changed

‎contrib/test_decoding/expected/ddl.out

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@@ -409,6 +409,24 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
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COMMIT
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(6 rows)
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-- check that DDL in aborted subtransactions handled correctly
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CREATE TABLE tr_sub_ddl(data int);
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BEGIN;
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SAVEPOINT a;
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ALTER TABLE tr_sub_ddl ALTER COLUMN data TYPE text;
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INSERT INTO tr_sub_ddl VALUES ('blah-blah');
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ROLLBACK TO SAVEPOINT a;
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ALTER TABLE tr_sub_ddl ALTER COLUMN data TYPE bigint;
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INSERT INTO tr_sub_ddl VALUES(43);
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COMMIT;
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SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
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data
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--------------------------------------------------
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BEGIN
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table public.tr_sub_ddl: INSERT: data[bigint]:43
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COMMIT
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(3 rows)
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/*
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* Check whether treating a table as a catalog table works somewhat
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*/

‎contrib/test_decoding/sql/ddl.sql

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@@ -234,6 +234,19 @@ INSERT INTO tr_sub(path) VALUES ('5-top-1-#1');
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COMMIT;
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SELECT dataFROM pg_logical_slot_get_changes('regression_slot',NULL,NULL,'include-xids','0','skip-empty-xacts','1');
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-- check that DDL in aborted subtransactions handled correctly
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CREATETABLEtr_sub_ddl(dataint);
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BEGIN;
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SAVEPOINT a;
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ALTERTABLE tr_sub_ddl ALTER COLUMN data TYPEtext;
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INSERT INTO tr_sub_ddlVALUES ('blah-blah');
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ROLLBACK TO SAVEPOINT a;
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ALTERTABLE tr_sub_ddl ALTER COLUMN data TYPEbigint;
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INSERT INTO tr_sub_ddlVALUES(43);
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COMMIT;
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SELECT dataFROM pg_logical_slot_get_changes('regression_slot',NULL,NULL,'include-xids','0','skip-empty-xacts','1');
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‎src/backend/replication/logical/reorderbuffer.c

Lines changed: 9 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1326,15 +1326,19 @@ ReorderBufferBuildTupleCidHash(ReorderBuffer *rb, ReorderBufferTXN *txn)
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}
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else
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{
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/*
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* Maybe we already saw this tuple before in this transaction,
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* but if so it must have the same cmin.
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*/
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Assert(ent->cmin==change->data.tuplecid.cmin);
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Assert(ent->cmax==InvalidCommandId||
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ent->cmax==change->data.tuplecid.cmax);
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/*
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* if the tuple got valid in this transaction and now got deleted
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* we already have a valid cmin stored. The cmax will be
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* InvalidCommandId though.
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* cmax may be initially invalid, but once set it can only grow,
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* and never become invalid again.
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*/
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Assert((ent->cmax==InvalidCommandId)||
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((change->data.tuplecid.cmax!=InvalidCommandId)&&
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(change->data.tuplecid.cmax>ent->cmax)));
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ent->cmax=change->data.tuplecid.cmax;
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}
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}

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