Set join_collapse_limit default value to the same as used in PostgreSQL 14 #1525
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…QL 14 The default value of join_collapse_limit was 20. When this value is set and the query contains about 20 joins (see added test), Postgres query optimizer cannot build a plan during hours and consumes a lot of memory, because the planner checks a lot of possible ways to join the tables. When join_collapse_limit is 8, the query plan is built in reasonable time.
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I suggest join_collapse_limit=8 to reduce the difference from PostgreSQL 14, but you can consider slightly larger values. In the table below there are time and memory consumption to process the query from the test.
Query processing time was got using |
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The default value of join_collapse_limit was 20. When this value is set and
the query contains about 20 joins (see added test), Postgres query optimizer
cannot build a plan during hours and consumes a lot of memory, because the
planner checks a lot of possible ways to join the tables.
When join_collapse_limit is 8, the query plan is built in reasonable time.