We have a performance problem accessing one of our tables, I think because the statistics are out of date. The table is fairly large, on the order of 100M rows or so. The general structure of the table is as follows:
Column | Type | Modifiers -------------------+--------------------------+------------------------------------------------ id | bigint | not null default nextval('foo_id_seq'::regclass) record_id | text | account_id | bigint | not null With indexes: "foo_pkey" PRIMARY KEY, btree (id) "uq_account_id_record_id" UNIQUE CONSTRAINT, btree (account_id, record_id) This table is almost always queried using a combination of (account_id, record_id) and is generally pretty fast. However, under certain loads, the query becomes slower and slower as time goes on. The workload that causes this to happen is when data for a new account_id is being inserted into the table. This will happen in rapid succession and may insert millions of rows over the course of several hours. The pattern that I notice when this happens is that the CPU on DB will be pegged much higher than usual, and the query to lookup records for the (account_id, record_id) combo will steadily rise from <1ms to more then 2 or 3 seconds over time. The fix I have employed to restore the speed of the query after I notice it is happening is to manually issue a VACUUM ANALYZE on the table. After the analyze is done, the query returns to its normal speed. I am looking for suggestions for how to tune, or perhaps automatically detect this pattern, so that I don't have to manually intervene whenever this happens. Here are my autovacuum settings: name | setting | unit -------------------------------------+-----------+------ autovacuum | on | autovacuum_analyze_scale_factor | 0.05 | autovacuum_analyze_threshold | 50 | autovacuum_freeze_max_age | 200000000 | autovacuum_max_workers | 3 | autovacuum_multixact_freeze_max_age | 400000000 | autovacuum_naptime | 30 | s autovacuum_vacuum_cost_delay | 20 | ms autovacuum_vacuum_cost_limit | -1 | autovacuum_vacuum_scale_factor | 0.1 | autovacuum_vacuum_threshold | 50 | autovacuum_work_mem | -1 | kB We're using 9.4.4 (RDS)