From f5f9a760a3bc2be95f8716e476150ce128efa22b Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Tue, 12 Feb 2019 18:42:37 -0300 Subject: [PATCH] Relax overly strict assertion Ever since its birth, ReorderBufferBuildTupleCidHash() has contained an assertion that a catalog tuple cannot change Cmax after acquiring one. But that's wrong: if a subtransaction executes DDL that affects that catalog tuple, and later aborts and another DDL affects the same tuple, it will change Cmax. Relax the assertion to merely verify that the Cmax remains valid and monotonically increasing, instead. Add a test that tickles the relevant code. Diagnosed by, and initial patch submitted by: Arseny Sher Co-authored-by: Arseny Sher Discussion: https://postgr.es/m/874l9p8hyw.fsf@ars-thinkpad --- contrib/test_decoding/expected/ddl.out | 18 ++++++++++++++++++ contrib/test_decoding/sql/ddl.sql | 13 +++++++++++++ .../replication/logical/reorderbuffer.c | 14 +++++++++----- 3 files changed, 40 insertions(+), 5 deletions(-) diff --git a/contrib/test_decoding/expected/ddl.out b/contrib/test_decoding/expected/ddl.out index 1e22c1eefc1..a5292c358aa 100644 --- a/contrib/test_decoding/expected/ddl.out +++ b/contrib/test_decoding/expected/ddl.out @@ -405,6 +405,24 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc COMMIT (6 rows) +-- check that DDL in aborted subtransactions handled correctly +CREATE TABLE tr_sub_ddl(data int); +BEGIN; +SAVEPOINT a; +ALTER TABLE tr_sub_ddl ALTER COLUMN data TYPE text; +INSERT INTO tr_sub_ddl VALUES ('blah-blah'); +ROLLBACK TO SAVEPOINT a; +ALTER TABLE tr_sub_ddl ALTER COLUMN data TYPE bigint; +INSERT INTO tr_sub_ddl VALUES(43); +COMMIT; +SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1'); + data +-------------------------------------------------- + BEGIN + table public.tr_sub_ddl: INSERT: data[bigint]:43 + COMMIT +(3 rows) + /* * Check whether treating a table as a catalog table works somewhat */ diff --git a/contrib/test_decoding/sql/ddl.sql b/contrib/test_decoding/sql/ddl.sql index 057dae056be..6a3e33e0810 100644 --- a/contrib/test_decoding/sql/ddl.sql +++ b/contrib/test_decoding/sql/ddl.sql @@ -235,6 +235,19 @@ INSERT INTO tr_sub(path) VALUES ('5-top-1-#1'); COMMIT; +SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1'); + +-- check that DDL in aborted subtransactions handled correctly +CREATE TABLE tr_sub_ddl(data int); +BEGIN; +SAVEPOINT a; +ALTER TABLE tr_sub_ddl ALTER COLUMN data TYPE text; +INSERT INTO tr_sub_ddl VALUES ('blah-blah'); +ROLLBACK TO SAVEPOINT a; +ALTER TABLE tr_sub_ddl ALTER COLUMN data TYPE bigint; +INSERT INTO tr_sub_ddl VALUES(43); +COMMIT; + SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1'); diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c index 518703141fa..392757001f9 100644 --- a/src/backend/replication/logical/reorderbuffer.c +++ b/src/backend/replication/logical/reorderbuffer.c @@ -1334,15 +1334,19 @@ ReorderBufferBuildTupleCidHash(ReorderBuffer *rb, ReorderBufferTXN *txn) } else { + /* + * Maybe we already saw this tuple before in this transaction, + * but if so it must have the same cmin. + */ Assert(ent->cmin == change->data.tuplecid.cmin); - Assert(ent->cmax == InvalidCommandId || - ent->cmax == change->data.tuplecid.cmax); /* - * if the tuple got valid in this transaction and now got deleted - * we already have a valid cmin stored. The cmax will be - * InvalidCommandId though. + * cmax may be initially invalid, but once set it can only grow, + * and never become invalid again. */ + Assert((ent->cmax == InvalidCommandId) || + ((change->data.tuplecid.cmax != InvalidCommandId) && + (change->data.tuplecid.cmax > ent->cmax))); ent->cmax = change->data.tuplecid.cmax; } }