Postgres partial index on IS NULL not working












0















CREATE TABLE tickets (
id bigserial primary key,
state character varying,
closed timestamp
);

CREATE INDEX "state_index" ON "tickets" ("state")
WHERE ((state)::text = 'open'::text));


A query with a condition on state performs well using an index scan as expected:



explain analyze select * from tickets where state = 'open';

Index Scan using state_index on tickets (cost=0.29..16093.57 rows=36599 width=212) (actual time=0.025..22.875 rows=37346 loops=1)
Planning time: 0.212 ms
Execution time: 25.697 ms


I am trying to achieve the same or better performance for the query with the condition closed IS NULL:



select * from tickets where closed IS NULL;


However, my partial indexes does not result in a single index scan like the first query.



CREATE INDEX  "closed_index" ON "tickets"  ("closed") WHERE (closed IS NULL)

explain analyze select * from tickets where closed IS NULL;

Bitmap Heap Scan on tickets (cost=604.22..38697.91 rows=36559 width=212) (actual time=12.879..48.780 rows=37348 loops=1)
Recheck Cond: (closed IS NULL)
Heap Blocks: exact=14757
-> Bitmap Index Scan on closed_index (cost=0.00..595.09 rows=36559 width=0) (actual time=7.585..7.585 rows=37348 loops=1)
Planning time: 4.831 ms
Execution time: 52.068 ms








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    CREATE TABLE tickets (
    id bigserial primary key,
    state character varying,
    closed timestamp
    );

    CREATE INDEX "state_index" ON "tickets" ("state")
    WHERE ((state)::text = 'open'::text));


    A query with a condition on state performs well using an index scan as expected:



    explain analyze select * from tickets where state = 'open';

    Index Scan using state_index on tickets (cost=0.29..16093.57 rows=36599 width=212) (actual time=0.025..22.875 rows=37346 loops=1)
    Planning time: 0.212 ms
    Execution time: 25.697 ms


    I am trying to achieve the same or better performance for the query with the condition closed IS NULL:



    select * from tickets where closed IS NULL;


    However, my partial indexes does not result in a single index scan like the first query.



    CREATE INDEX  "closed_index" ON "tickets"  ("closed") WHERE (closed IS NULL)

    explain analyze select * from tickets where closed IS NULL;

    Bitmap Heap Scan on tickets (cost=604.22..38697.91 rows=36559 width=212) (actual time=12.879..48.780 rows=37348 loops=1)
    Recheck Cond: (closed IS NULL)
    Heap Blocks: exact=14757
    -> Bitmap Index Scan on closed_index (cost=0.00..595.09 rows=36559 width=0) (actual time=7.585..7.585 rows=37348 loops=1)
    Planning time: 4.831 ms
    Execution time: 52.068 ms








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      CREATE TABLE tickets (
      id bigserial primary key,
      state character varying,
      closed timestamp
      );

      CREATE INDEX "state_index" ON "tickets" ("state")
      WHERE ((state)::text = 'open'::text));


      A query with a condition on state performs well using an index scan as expected:



      explain analyze select * from tickets where state = 'open';

      Index Scan using state_index on tickets (cost=0.29..16093.57 rows=36599 width=212) (actual time=0.025..22.875 rows=37346 loops=1)
      Planning time: 0.212 ms
      Execution time: 25.697 ms


      I am trying to achieve the same or better performance for the query with the condition closed IS NULL:



      select * from tickets where closed IS NULL;


      However, my partial indexes does not result in a single index scan like the first query.



      CREATE INDEX  "closed_index" ON "tickets"  ("closed") WHERE (closed IS NULL)

      explain analyze select * from tickets where closed IS NULL;

      Bitmap Heap Scan on tickets (cost=604.22..38697.91 rows=36559 width=212) (actual time=12.879..48.780 rows=37348 loops=1)
      Recheck Cond: (closed IS NULL)
      Heap Blocks: exact=14757
      -> Bitmap Index Scan on closed_index (cost=0.00..595.09 rows=36559 width=0) (actual time=7.585..7.585 rows=37348 loops=1)
      Planning time: 4.831 ms
      Execution time: 52.068 ms








      share














      CREATE TABLE tickets (
      id bigserial primary key,
      state character varying,
      closed timestamp
      );

      CREATE INDEX "state_index" ON "tickets" ("state")
      WHERE ((state)::text = 'open'::text));


      A query with a condition on state performs well using an index scan as expected:



      explain analyze select * from tickets where state = 'open';

      Index Scan using state_index on tickets (cost=0.29..16093.57 rows=36599 width=212) (actual time=0.025..22.875 rows=37346 loops=1)
      Planning time: 0.212 ms
      Execution time: 25.697 ms


      I am trying to achieve the same or better performance for the query with the condition closed IS NULL:



      select * from tickets where closed IS NULL;


      However, my partial indexes does not result in a single index scan like the first query.



      CREATE INDEX  "closed_index" ON "tickets"  ("closed") WHERE (closed IS NULL)

      explain analyze select * from tickets where closed IS NULL;

      Bitmap Heap Scan on tickets (cost=604.22..38697.91 rows=36559 width=212) (actual time=12.879..48.780 rows=37348 loops=1)
      Recheck Cond: (closed IS NULL)
      Heap Blocks: exact=14757
      -> Bitmap Index Scan on closed_index (cost=0.00..595.09 rows=36559 width=0) (actual time=7.585..7.585 rows=37348 loops=1)
      Planning time: 4.831 ms
      Execution time: 52.068 ms






      postgresql index postgresql-performance





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      asked 8 mins ago









      GeekJockGeekJock

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