Jan Wieck <j...@wi3ck.info> wrote: > The problem is a cache introduced in commit 45ba4247 that improves
That's a bit off; 45ba424f seems to be what you mean. > foreign key lookups during bulk updates when the FK value does not > change. When restoring a schema dump from a database with many (say > 100,000) foreign keys, this cache is growing very big and every ALTER > TABLE command is causing a InvalidateConstraintCacheCallBack(), which > does a sequential hash table scan. > > The patch uses a heuristic method of detecting when the hash table > should be destroyed and recreated. InvalidateConstraintCacheCallBack() > adds the current size of the hash table to a counter. When that sum > reaches 1,000,000, the hash table is flushed. This improves the schema > restore of a database with 100,000 foreign keys by factor 3. > > According to my tests the patch does not interfere with the bulk > updates, the original feature was supposed to improve. In the real-world customer case that caused you to look into this, I thought 45ba424f drove schema-only restore time from 2 hours to about 25 hours, and that this patch takes it back down to 2 hours. Am I remembering right? And this came about because it added 20-some hours to a pg_upgrade run? If there are no objections, I will push this as a bug fix back to 9.3, where the performance regression was introduced. -- Kevin Grittner EDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
