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e9edc1ba0b
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
103 lines
3.9 KiB
PL/PgSQL
103 lines
3.9 KiB
PL/PgSQL
-- 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$,
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(SELECT repeat(string_agg(to_char(g.i, 'FM0000'), ''), 50) FROM generate_series(1, 500) g(i))));
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SELECT exec(
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format($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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SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
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BEGIN;
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INSERT INTO replication_example(somedata) VALUES (2);
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ALTER TABLE replication_example ADD COLUMN testcolumn1 int;
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INSERT INTO replication_example(somedata, testcolumn1) VALUES (3, 1);
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COMMIT;
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BEGIN;
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INSERT INTO replication_example(somedata) VALUES (3);
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ALTER TABLE replication_example ADD COLUMN testcolumn2 int;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn2) VALUES (4, 2, 1);
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COMMIT;
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VACUUM FULL pg_am;
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VACUUM FULL pg_amop;
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VACUUM FULL pg_proc;
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VACUUM FULL pg_opclass;
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VACUUM FULL pg_type;
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VACUUM FULL pg_index;
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VACUUM FULL pg_database;
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-- repeated rewrites that fail
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BEGIN;
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CLUSTER pg_class USING pg_class_oid_index;
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CLUSTER pg_class USING pg_class_oid_index;
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ROLLBACK;
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-- repeated rewrites that succeed
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BEGIN;
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CLUSTER pg_class USING pg_class_oid_index;
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CLUSTER pg_class USING pg_class_oid_index;
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CLUSTER pg_class USING pg_class_oid_index;
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COMMIT;
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-- repeated rewrites in different transactions
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VACUUM FULL pg_class;
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VACUUM FULL pg_class;
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INSERT INTO replication_example(somedata, testcolumn1) VALUES (5, 3);
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BEGIN;
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INSERT INTO replication_example(somedata, testcolumn1) VALUES (6, 4);
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ALTER TABLE replication_example ADD COLUMN testcolumn3 int;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn3) VALUES (7, 5, 1);
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COMMIT;
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-- make old files go away
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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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-- 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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