3 Commits (6eebfdc38b173edcd179f422cf7083383edb24bc)

Author	SHA1	Message	Date
Andres Freund	e9edc1ba0b	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	7 years ago
Andres Freund	d6fa44fce7	Add skip-empty-xacts option to test_decoding for use in the regression tests. ... The regression tests for contrib/test_decoding regularly failed on postgres instances that were very slow. Either because the hardware itself was slow or because very expensive debugging options like CLOBBER_CACHE_ALWAYS were used. The reason they failed was just that some additional transactions were decoded. Analyze and vacuum, triggered by autovac. To fix just add a option to test_decoding to only display transactions in which a change was actually displayed. That's not pretty because it removes information from the tests; but better than constantly failing tests in very likely harmless ways. Backpatch to 9.4 where logical decoding was introduced. Discussion: 20140629142511.GA26930@awork2.anarazel.de	12 years ago
Robert Haas	b89e151054	Introduce logical decoding. ... This feature, building on previous commits, allows the write-ahead log stream to be decoded into a series of logical changes; that is, inserts, updates, and deletes and the transactions which contain them. It is capable of handling decoding even across changes to the schema of the effected tables. The output format is controlled by a so-called "output plugin"; an example is included. To make use of this in a real replication system, the output plugin will need to be modified to produce output in the format appropriate to that system, and to perform filtering. Currently, information can be extracted from the logical decoding system only via SQL; future commits will add the ability to stream changes via walsender. Andres Freund, with review and other contributions from many other people, including Álvaro Herrera, Abhijit Menon-Sen, Peter Gheogegan, Kevin Grittner, Robert Haas, Heikki Linnakangas, Fujii Masao, Abhijit Menon-Sen, Michael Paquier, Simon Riggs, Craig Ringer, and Steve Singer.	12 years ago