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MirrorHub/synapse

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Improve performance of _get_state_groups_from_groups_txn (#7567) The query keeps showing up in my slow query log. This changes the plan under the top-level Sort node from ``` WindowAgg (cost=280335.88..292963.15 rows=561212 width=80) (actual time=138.651..160.562 rows=27112 loops=1) -> Sort (cost=280335.88..281738.91 rows=561212 width=84) (actual time=138.597..140.622 rows=27112 loops=1) Sort Key: state_groups_state.type, state_groups_state.state_key, state_groups_state.state_group Sort Method: quicksort Memory: 4581kB -> Nested Loop (cost=2.83..226745.22 rows=561212 width=84) (actual time=21.548..47.657 rows=27112 loops=1) -> HashAggregate (cost=2.27..3.28 rows=101 width=8) (actual time=21.526..21.535 rows=20 loops=1) Group Key: state.state_group -> CTE Scan on state (cost=0.00..2.02 rows=101 width=8) (actual time=21.280..21.493 rows=20 loops=1) -> Index Scan using state_groups_state_type_idx on state_groups_state (cost=0.56..2189.40 rows=5557 width=84) (actual time=0.005..0.991 rows=1356 loops=20) Index Cond: (state_group = state.state_group) ``` to ``` Nested Loop (cost=2.83..226745.22 rows=561212 width=84) (actual time=24.194..52.834 rows=27112 loops=1) -> HashAggregate (cost=2.27..3.28 rows=101 width=8) (actual time=24.130..24.138 rows=20 loops=1) Group Key: state.state_group -> CTE Scan on state (cost=0.00..2.02 rows=101 width=8) (actual time=23.887..24.113 rows=20 loops=1) -> Index Scan using state_groups_state_type_idx on state_groups_state (cost=0.56..2189.40 rows=5557 width=84) (actual time=0.016..1.159 rows=1356 loops=20) Index Cond: (state_group = state.state_group) ``` This cuts the execution time from ~190ms to ~130ms, i.e. a reduction of ~30%. The full plans are visualised at https://explain.depesz.com/s/WpbT and https://explain.depesz.com/s/KlEk Signed-off-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>

2020-06-01 16:23:43 +02:00

Improve query performance for fetching state from a PostgreSQL database.