From 350cdcd5e6dd505454435af8d7640a4b5042fcfd 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 1ead37a7291..a04038555ef 100644 --- a/contrib/test_decoding/expected/ddl.out +++ b/contrib/test_decoding/expected/ddl.out @@ -338,6 +338,24 @@ 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 7f3446e70d4..ae9835fe869 100644 --- a/contrib/test_decoding/sql/ddl.sql +++ b/contrib/test_decoding/sql/ddl.sql @@ -215,6 +215,19 @@ 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 42d44816241..fbc2b6fe1ee 100644 --- a/src/backend/replication/logical/reorderbuffer.c +++ b/src/backend/replication/logical/reorderbuffer.c @@ -1326,15 +1326,19 @@ 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; } }