[PostGIS] #5984: PostGIS selectivity is screwing up queries and forcing it to choose a spatial index when it's inappropriate

[PostGIS]

#5984: PostGIS selectivity is screwing up queries and forcing it to choose a
spatial index when it's inappropriate
-----------------------+---------------------------
  Reporter:  robe      |      Owner:  pramsey
      Type:  defect    |     Status:  new
  Priority:  critical  |  Milestone:  PostGIS 3.4.5
 Component:  postgis   |    Version:  3.5.x
Resolution:            |   Keywords:
-----------------------+---------------------------
Comment (by robe):

 Here is a better query to use, one that uses an id in the data set
 There you can see 42 rows had to be removed by a filter call

 {{{
 EXPLAIN ANALYZE SELECT wn.way_id FROM test_way_nodes AS wn INNER JOIN
 test_nodes AS n ON wn.node_id = n.id     WHERE wn.node_id = 12862767139
 AND ST_Contains(ST_GeomFromEWKT('SRID=4326;POLYGON((6.1198199
 52.612195500000006,6.1198199 53.2038323,7.09
 27397 53.2038323,7.0927397 52.612195500000006,6.1198199
 52.612195500000006))'), n.geom);
 QUERY PLAN

 --------------------
  Nested Loop  (cost=0.70..29.25 rows=1 width=8) (actual time=0.349..0.350
 rows=0 loops=1)
    ->  Index Scan using idx_test_way_nodes_node_id on test_way_nodes wn
 (cost=0.42..8.44 rows=1 width=16) (actual time=0.075..0.076 rows=1
 loops=1)
          Index Cond: (node_id = '12862767139'::bigint)
    ->  Index Scan using idx_test_nodes_geom on test_nodes n
 (cost=0.28..20.80 rows=1 width=8) (actual time=0.271..0.271 rows=0
 loops=1)
          Index Cond: (geom @
 '0103000020E61000000100000005000000D5A35F11B27A184013A1116C5C4E4A40D5A35F11B27A18402A2F432D179A4A40D529EA27F75E1C402A2F432D179A4A40D529EA27F75E1C4013A1116C5C4E4A40D5A35F11B27A184013A1116C5C4E4A40'::geometry)
          Filter: ((id = '12862767139'::bigint) AND
 st_contains('0103000020E61000000100000005000000D5A35F11B27A184013A1116C5C4E4A40D5A35F11B27A18402A2F432D179A4A40D529EA27F75E1C402A2F432D179A4A40D529EA27F75E1C4013A1116C5C4E4A40D5A35F11B27A184013A1116C5C4E4A4
 0'::geometry, geom))
          Rows Removed by Filter: 43
  Planning Time: 2.873 ms
  Execution Time: 0.472 ms
 (9 rows)

 }}}


 Verses query that prevents spatial index usage

 {{{
 EXPLAIN ANALYZE SELECT wn.way_id FROM test_way_nodes AS wn INNER JOIN
 test_nodes AS n ON wn.node_id = n.id     WHERE wn.node_id = 12862767139
 AND _ST_Contains(ST_GeomFromEWKT('SRID=4326;POLYGON((6.1198199
 52.612195500000006,6.1198199 53.2038323,7.0
 927397 53.2038323,7.0927397 52.612195500000006,6.1198199
 52.612195500000006))'), n.geom);
 QUERY PLAN
 -------------------------------------------------
  Nested Loop  (cost=0.84..29.38 rows=1 width=8) (actual time=0.132..0.133
 rows=0 loops=1)
    ->  Index Scan using idx_test_way_nodes_node_id on test_way_nodes wn
 (cost=0.42..8.44 rows=1 width=16) (actual time=0.017..0.018 rows=1
 loops=1)
          Index Cond: (node_id = '12862767139'::bigint)
    ->  Index Scan using test_nodes_pkey on test_nodes n  (cost=0.42..20.94
 rows=1 width=8) (actual time=0.111..0.111 rows=0 loops=1)
          Index Cond: (id = '12862767139'::bigint)
          Filter:
 _st_contains('0103000020E61000000100000005000000D5A35F11B27A184013A1116C5C4E4A40D5A35F11B27A18402A2F432D179A4A40D529EA27F75E1C402A2F432D179A4A40D529EA27F75E1C4013A1116C5C4E4A40D5A35F11B27A184013A1116C5C4E4A40'::geometry,
 geom)
  Planning Time: 0.232 ms
  Execution Time: 0.208 ms
 (8 rows)
 }}}
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5984#comment:2>
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