Incorrect index being used - Mailing list pgsql-general

Hi PostgreSQL community,

I have the following query, run immediately after executing VACUUM in
the database. There is only one connection to the database.

The query runs for much longer than I expect it to run for, and I think
this is due to it using the incorrect subplan. As you can see, subplans
1 and 3 make use of and index, but these subplans are not used.
Subplans  and 4 are seqscan, and they are used.

How can I get PostgreSQL to use subplan 1 and 3?

Thanks,
Jesse

testdb=> explain analyse SELECT * FROM ARCHIVE_DOCUMENT AS r0 WHERE r0.NODE_ID = 29 AND r0.ARCHIVE_DATE >= '2013-07-08
18:28:00'AND (EXISTS (SELECT r1.* FROM ARCHIVE_DOCUMENT_INDEX AS r1 WHERE r1.ARCHIVE_ID = r0.ID AND r1.NODE_ID =
r0.NODE_IDAND r1.VALUE = 'BSH70002152' ) OR EXISTS ( SELECT r2.* FROM ARCHIVE_DOCUMENT_INDEX AS r2 WHERE r2.ARCHIVE_ID
=r0.ID AND r2.NODE_ID = r0.NODE_ID AND r2.VALUE = 'TC212592' ) ) ORDER BY r0.ARCHIVE_DATE DESC LIMIT 10; 

                                                                                              QUERY PLAN


------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  Limit  (cost=0.56..151.79 rows=10 width=122) (actual time=44601.350..97649.196 rows=2 loops=1)

    ->  Index Scan Backward using idx_archive_document_x_node_id_archive_date on archive_document r0
(cost=0.56..8258406.24rows=546105 width=122) (actual time=44601.33 

          Index Cond: ((node_id = 29) AND (archive_date >= '2013-07-08 18:28:00'::timestamp without time zone))

          Filter: ((alternatives: SubPlan 1 or hashed SubPlan 2) OR (alternatives: SubPlan 3 or hashed SubPlan 4))

          Rows Removed by Filter: 710851

          SubPlan 1

            ->  Index Only Scan using archive_document_index_x_archive_id_node_id_value on archive_document_index r1
(cost=0.57..4.59rows=1 width=0) (never executed) 

                  Index Cond: ((archive_id = r0.id) AND (node_id = r0.node_id) AND (value = 'BSH70002152'::text))

                  Heap Fetches: 0

          SubPlan 2

            ->  Seq Scan on archive_document_index r1_1  (cost=0.00..1958104.00 rows=1520 width=16) (actual
time=44418.383..44558.293rows=4 loops=1) 

                  Filter: ((value)::text = 'BSH70002152'::text)

                  Rows Removed by Filter: 95009919

          SubPlan 3

            ->  Index Only Scan using archive_document_index_x_archive_id_node_id_value on archive_document_index r2
(cost=0.57..4.59rows=1 width=0) (never executed) 

                  Index Cond: ((archive_id = r0.id) AND (node_id = r0.node_id) AND (value = 'TC212592'::text))

                  Heap Fetches: 0

          SubPlan 4

            ->  Seq Scan on archive_document_index r2_1  (cost=0.00..1958104.00 rows=1520 width=16) (actual
time=41659.464..41663.342rows=1 loops=1) 

                  Filter: ((value)::text = 'TC212592'::text)

                  Rows Removed by Filter: 95009922

  Total runtime: 97683.836 ms

(22 rows)