Fix logical decoding error when system table w/ toast is repeatedly rewritten.
Repeatedly rewriting a mapped catalog table with VACUUM FULL or CLUSTER could cause logical decoding to fail with: ERROR, "could not map filenode \"%s\" to relation OID" To trigger the problem the rewritten catalog had to have live tuples with toasted columns. The problem was triggered as during catalog table rewrites the heap_insert() check that prevents logical decoding information to be emitted for system catalogs, failed to treat the new heap's toast table as a system catalog (because the new heap is not recognized as a catalog table via RelationIsLogicallyLogged()). The relmapper, in contrast to the normal catalog contents, does not contain historical information. After a single rewrite of a mapped table the new relation is known to the relmapper, but if the table is rewritten twice before logical decoding occurs, the relfilenode cannot be mapped to a relation anymore. Which then leads us to error out. This only happens for toast tables, because the main table contents aren't re-inserted with heap_insert(). The fix is simple, add a new heap_insert() flag that prevents logical decoding information from being emitted, and accept during decoding that there might not be tuple data for toast tables. Unfortunately that does not fix pre-existing logical decoding errors. Doing so would require not throwing an error when a filenode cannot be mapped to a relation during decoding, and that seems too likely to hide bugs. If it's crucial to fix decoding for an existing slot, temporarily changing the ERROR in ReorderBufferCommit() to a WARNING appears to be the best fix. Author: Andres Freund Discussion: https://postgr.es/m/20180914021046.oi7dm4ra3ot2g2kt@alap3.anarazel.de Backpatch: 9.4-, where logical decoding was introduced
This commit is contained in:
Andres Freund
parent
ef493055b6
commit
e9edc1ba0b
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@ -1,6 +1,61 @@
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-- predictability
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SET synchronous_commit = on;
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DROP TABLE IF EXISTS replication_example;
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-- Ensure there's tables with toast datums. To do so, we dynamically
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-- create a function returning a large textblob. We want tables of
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-- different kinds: mapped catalog table, unmapped catalog table,
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-- shared catalog table and usertable.
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CREATE FUNCTION exec(text) returns void language plpgsql volatile
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AS $f$
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BEGIN
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EXECUTE $1;
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END;
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$f$;
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CREATE ROLE justforcomments NOLOGIN;
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SELECT exec(
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format($outer$CREATE FUNCTION iamalongfunction() RETURNS TEXT IMMUTABLE LANGUAGE SQL AS $f$SELECT text %L$f$$outer$,
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(SELECT repeat(string_agg(to_char(g.i, 'FM0000'), ''), 50) FROM generate_series(1, 500) g(i))));
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exec
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------
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(1 row)
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SELECT exec(
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format($outer$COMMENT ON FUNCTION iamalongfunction() IS %L$outer$,
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iamalongfunction()));
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exec
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------
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(1 row)
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SELECT exec(
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format($outer$COMMENT ON ROLE JUSTFORCOMMENTS IS %L$outer$,
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iamalongfunction()));
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exec
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------
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(1 row)
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CREATE TABLE iamalargetable AS SELECT iamalongfunction() longfunctionoutput;
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-- verify toast usage
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SELECT pg_relation_size((SELECT reltoastrelid FROM pg_class WHERE oid = 'pg_proc'::regclass)) > 0;
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?column?
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----------
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t
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(1 row)
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SELECT pg_relation_size((SELECT reltoastrelid FROM pg_class WHERE oid = 'pg_description'::regclass)) > 0;
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?column?
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----------
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t
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(1 row)
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SELECT pg_relation_size((SELECT reltoastrelid FROM pg_class WHERE oid = 'pg_shdescription'::regclass)) > 0;
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?column?
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----------
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t
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(1 row)
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SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
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?column?
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----------
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@ -76,6 +131,23 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
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COMMIT
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(15 rows)
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-- trigger repeated rewrites of a system catalog with a toast table,
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-- that previously was buggy: 20180914021046.oi7dm4ra3ot2g2kt@alap3.anarazel.de
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VACUUM FULL pg_proc; VACUUM FULL pg_description; VACUUM FULL pg_shdescription; VACUUM FULL iamalargetable;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn3) VALUES (8, 6, 1);
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VACUUM FULL pg_proc; VACUUM FULL pg_description; VACUUM FULL pg_shdescription; VACUUM FULL iamalargetable;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn3) VALUES (9, 7, 1);
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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.replication_example: INSERT: id[integer]:9 somedata[integer]:8 text[character varying]:null testcolumn1[integer]:6 testcolumn2[integer]:null testcolumn3[integer]:1
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COMMIT
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BEGIN
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table public.replication_example: INSERT: id[integer]:10 somedata[integer]:9 text[character varying]:null testcolumn1[integer]:7 testcolumn2[integer]:null testcolumn3[integer]:1
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COMMIT
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(6 rows)
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SELECT pg_drop_replication_slot('regression_slot');
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pg_drop_replication_slot
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--------------------------
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@ -83,3 +155,6 @@ SELECT pg_drop_replication_slot('regression_slot');
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(1 row)
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DROP TABLE IF EXISTS replication_example;
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DROP FUNCTION iamalongfunction();
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DROP FUNCTION exec(text);
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DROP ROLE justforcomments;
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@ -3,6 +3,35 @@ SET synchronous_commit = on;
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DROP TABLE IF EXISTS replication_example;
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-- Ensure there's tables with toast datums. To do so, we dynamically
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-- create a function returning a large textblob. We want tables of
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-- different kinds: mapped catalog table, unmapped catalog table,
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-- shared catalog table and usertable.
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CREATE FUNCTION exec(text) returns void language plpgsql volatile
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AS $f$
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BEGIN
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EXECUTE $1;
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END;
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$f$;
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CREATE ROLE justforcomments NOLOGIN;
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SELECT exec(
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format($outer$CREATE FUNCTION iamalongfunction() RETURNS TEXT IMMUTABLE LANGUAGE SQL AS $f$SELECT text %L$f$$outer$,
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(SELECT repeat(string_agg(to_char(g.i, 'FM0000'), ''), 50) FROM generate_series(1, 500) g(i))));
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SELECT exec(
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format($outer$COMMENT ON FUNCTION iamalongfunction() IS %L$outer$,
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iamalongfunction()));
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SELECT exec(
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format($outer$COMMENT ON ROLE JUSTFORCOMMENTS IS %L$outer$,
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iamalongfunction()));
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CREATE TABLE iamalargetable AS SELECT iamalongfunction() longfunctionoutput;
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-- verify toast usage
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SELECT pg_relation_size((SELECT reltoastrelid FROM pg_class WHERE oid = 'pg_proc'::regclass)) > 0;
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SELECT pg_relation_size((SELECT reltoastrelid FROM pg_class WHERE oid = 'pg_description'::regclass)) > 0;
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SELECT pg_relation_size((SELECT reltoastrelid FROM pg_class WHERE oid = 'pg_shdescription'::regclass)) > 0;
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SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
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CREATE TABLE replication_example(id SERIAL PRIMARY KEY, somedata int, text varchar(120));
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INSERT INTO replication_example(somedata) VALUES (1);
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@ -57,6 +86,17 @@ COMMIT;
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CHECKPOINT;
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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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SELECT pg_drop_replication_slot('regression_slot');
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-- trigger repeated rewrites of a system catalog with a toast table,
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-- that previously was buggy: 20180914021046.oi7dm4ra3ot2g2kt@alap3.anarazel.de
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VACUUM FULL pg_proc; VACUUM FULL pg_description; VACUUM FULL pg_shdescription; VACUUM FULL iamalargetable;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn3) VALUES (8, 6, 1);
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VACUUM FULL pg_proc; VACUUM FULL pg_description; VACUUM FULL pg_shdescription; VACUUM FULL iamalargetable;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn3) VALUES (9, 7, 1);
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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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SELECT pg_drop_replication_slot('regression_slot');
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DROP TABLE IF EXISTS replication_example;
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DROP FUNCTION iamalongfunction();
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DROP FUNCTION exec(text);
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DROP ROLE justforcomments;
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@ -2435,6 +2435,11 @@ ReleaseBulkInsertStatePin(BulkInsertState bistate)
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* Speculatively inserted tuples behave as "value locks" of short duration,
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* used to implement INSERT .. ON CONFLICT.
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*
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* HEAP_INSERT_NO_LOGICAL force-disables the emitting of logical decoding
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* information for the tuple. This should solely be used during table rewrites
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* where RelationIsLogicallyLogged(relation) is not yet accurate for the new
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* relation.
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*
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* Note that most of these options will be applied when inserting into the
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* heap's TOAST table, too, if the tuple requires any out-of-line data. Only
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* HEAP_INSERT_SPECULATIVE is explicitly ignored, as the toast data does not
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@ -2563,7 +2568,8 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
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* page write, so make sure it's included even if we take a full-page
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* image. (XXX We could alternatively store a pointer into the FPW).
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*/
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if (RelationIsLogicallyLogged(relation))
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if (RelationIsLogicallyLogged(relation) &&
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!(options & HEAP_INSERT_NO_LOGICAL))
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{
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xlrec.flags |= XLH_INSERT_CONTAINS_NEW_TUPLE;
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bufflags |= REGBUF_KEEP_DATA;
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@ -2728,6 +2734,9 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
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bool need_tuple_data = RelationIsLogicallyLogged(relation);
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bool need_cids = RelationIsAccessibleInLogicalDecoding(relation);
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/* currently not needed (thus unsupported) for heap_multi_insert() */
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AssertArg(!(options & HEAP_INSERT_NO_LOGICAL));
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needwal = !(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation);
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saveFreeSpace = RelationGetTargetPageFreeSpace(relation,
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HEAP_DEFAULT_FILLFACTOR);
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@ -652,10 +652,23 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
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heaptup = tup;
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}
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else if (HeapTupleHasExternal(tup) || tup->t_len > TOAST_TUPLE_THRESHOLD)
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{
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int options = HEAP_INSERT_SKIP_FSM;
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if (!state->rs_use_wal)
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options |= HEAP_INSERT_SKIP_WAL;
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/*
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* The new relfilenode's relcache entrye doesn't have the necessary
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* information to determine whether a relation should emit data for
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* logical decoding. Force it to off if necessary.
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*/
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if (!RelationIsLogicallyLogged(state->rs_old_rel))
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options |= HEAP_INSERT_NO_LOGICAL;
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heaptup = toast_insert_or_update(state->rs_new_rel, tup, NULL,
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HEAP_INSERT_SKIP_FSM |
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(state->rs_use_wal ?
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0 : HEAP_INSERT_SKIP_WAL));
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options);
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}
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else
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heaptup = tup;
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@ -1527,8 +1527,16 @@ ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
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change->data.tp.relnode.relNode);
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/*
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* Catalog tuple without data, emitted while catalog was
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* in the process of being rewritten.
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* Mapped catalog tuple without data, emitted while
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* catalog table was in the process of being rewritten. We
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* can fail to look up the relfilenode, because the the
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* relmapper has no "historic" view, in contrast to normal
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* the normal catalog during decoding. Thus repeated
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* rewrites can cause a lookup failure. That's OK because
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* we do not decode catalog changes anyway. Normally such
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* tuples would be skipped over below, but we can't
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* identify whether the table should be logically logged
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* without mapping the relfilenode to the oid.
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*/
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if (reloid == InvalidOid &&
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change->data.tp.newtuple == NULL &&
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@ -1590,10 +1598,17 @@ ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
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* transaction's changes. Otherwise it will get
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* freed/reused while restoring spooled data from
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* disk.
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*
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* But skip doing so if there's no tuple-data. That
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* happens if a non-mapped system catalog with a toast
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* table is rewritten.
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*/
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dlist_delete(&change->node);
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ReorderBufferToastAppendChunk(rb, txn, relation,
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change);
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if (change->data.tp.newtuple != NULL)
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{
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dlist_delete(&change->node);
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ReorderBufferToastAppendChunk(rb, txn, relation,
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change);
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}
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}
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change_done:
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@ -29,6 +29,7 @@
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#define HEAP_INSERT_SKIP_FSM 0x0002
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#define HEAP_INSERT_FROZEN 0x0004
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#define HEAP_INSERT_SPECULATIVE 0x0008
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#define HEAP_INSERT_NO_LOGICAL 0x0010
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typedef struct BulkInsertStateData *BulkInsertState;
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