Shortcut performance can be low because of to_jsonb and jsonb_agg #194
Description
Shortcuts generates queries that have a performance penalty.
Both tables in the example below have a column that is a jsonb that can be large (few kb).
What do you think ?
select
With jsonb_agg
EXPLAIN (ANALYZE, BUFFERS, MEMORY)
SELECT coalesce(jsonb_agg(result), '[]') AS result FROM (SELECT to_jsonb("cache_article".*) AS result FROM "cache_article" LIMIT 10000) AS "sq_cache_article";Aggregate (cost=2673.82..2673.83 rows=1 width=32) (actual time=411.650..411.654 rows=1 loops=1)
Buffers: shared hit=2481
-> Limit (cost=0.00..2648.81 rows=10000 width=32) (actual time=0.145..105.108 rows=10000 loops=1)
Buffers: shared hit=2481
-> Seq Scan on cache_article (cost=0.00..25499.34 rows=96267 width=32) (actual time=0.144..103.799 rows=10000 loops=1)
Buffers: shared hit=2481
Planning:
Buffers: shared hit=103
Memory: used=19kB allocated=64kB
Planning Time: 0.828 ms
Execution Time: 424.653 ms
With to_jsonb
EXPLAIN (ANALYZE, BUFFERS, MEMORY)
SELECT to_jsonb("cache_article".*) AS result FROM "cache_article" LIMIT 10000;Limit (cost=0.00..2648.81 rows=10000 width=32) (actual time=0.172..144.909 rows=10000 loops=1)
Buffers: shared hit=2481
-> Seq Scan on cache_article (cost=0.00..25499.34 rows=96267 width=32) (actual time=0.171..143.755 rows=10000 loops=1)
Buffers: shared hit=2481
Planning:
Buffers: shared hit=94
Memory: used=8kB allocated=40kB
Planning Time: 0.759 ms
Execution Time: 145.645 ms
Execution Time: 94.797 ms
Without
EXPLAIN (ANALYZE, BUFFERS, MEMORY)
SELECT "cache_article".* AS result FROM "cache_article" LIMIT 10000;Limit (cost=0.00..2623.81 rows=10000 width=998) (actual time=0.033..14.960 rows=10000 loops=1)
Buffers: shared hit=2079
-> Seq Scan on cache_article (cost=0.00..25258.67 rows=96267 width=998) (actual time=0.031..14.139 rows=10000 loops=1)
Buffers: shared hit=2079
Planning:
Buffers: shared hit=94
Memory: used=9kB allocated=64kB
Planning Time: 0.758 ms
Execution Time: 15.479 ms
selectOne
With to_jsonb
EXPLAIN (ANALYSE, BUFFERS) SELECT to_jsonb("cache".*) AS result
FROM "cache"
WHERE (
"full_path" = '/doc/20002463' AND
"operation_id" = 'get-doc'
) LIMIT 1Limit (cost=0.55..8.57 rows=1 width=32) (actual time=109.022..109.024 rows=1 loops=1)
Buffers: shared hit=74
-> Index Scan using cache_pkey on cache (cost=0.55..8.57 rows=1 width=32) (actual time=109.020..109.020 rows=1 loops=1)
Index Cond: (((operation_id)::text = 'get-doc'::text) AND (full_path = '/doc/20002463'::text))
Buffers: shared hit=74
Planning:
Buffers: shared hit=180
Planning Time: 1.731 ms
Execution Time: 113.602 ms
Without
EXPLAIN (ANALYSE, BUFFERS) SELECT *
FROM "cache"
WHERE (
"full_path" = '/doc/20002463' AND
"operation_id" = 'get-doc'
) LIMIT 1Limit (cost=0.55..8.57 rows=1 width=1085) (actual time=0.076..0.077 rows=1 loops=1)
Buffers: shared hit=5
-> Index Scan using cache_pkey on cache (cost=0.55..8.57 rows=1 width=1085) (actual time=0.074..0.075 rows=1 loops=1)
Index Cond: (((operation_id)::text = 'get-doc'::text) AND (full_path = '/doc/20002463'::text))
Buffers: shared hit=5
Planning:
Buffers: shared hit=180
Planning Time: 1.189 ms
Execution Time: 0.167 ms