tbloom WHERE i2 = 898732 AND i5 = 123451;
                                                     QUERY PLAN
-------------------------------------------------------------------&zwsp;--------------------------------------------------
 Bitmap Heap Scan on tbloom  (cost=1792.00..1799.69 rows=2 width=24) (actual time=22.605..22.606 rows=0.00 loops=1)
   Recheck Cond: ((i2 = 898732) AND (i5 = 123451))
   Rows Removed by Index Recheck: 2300
   Heap Blocks: exact=2256
   Buffers: shared hit=21864
   ->  Bitmap Index Scan on bloomidx  (cost=0.00..178436.00 rows=1 width=0) (actual time=20.005..20.005 rows=2300.00 loops=1)
         Index Cond: ((i2 = 898732) AND (i5 = 123451))
         Index Searches: 1
         Buffers: shared hit=19608
 Planning Time: 0.099 ms
 Execution Time: 22.632 ms
(11 rows)
</programlisting>
  </para>

  <para>
   Now, the main problem with the btree search is that btree is inefficient
   when the search conditions do not constrain the leading index column(s).
   A better strategy for btree is to create a separate index on each column.
   Then the planner will choose something like this:
<programlisting>
=# CREATE INDEX btreeidx1 ON tbloom (i1);
CREATE INDEX
=# CREATE INDEX btreeidx2 ON tbloom (i2);
CREATE INDEX
=# CREATE INDEX btreeidx3 ON tbloom (i3);
CREATE INDEX
=# CREATE INDEX btreeidx4 ON tbloom (i4);
CREATE INDEX
=# CREATE INDEX btreeidx5 ON tbloom (i5);
CREATE INDEX
=# CREATE INDEX btreeidx6 ON tbloom (i6);
CREATE INDEX
=# EXPLAIN ANALYZE SELECT * FROM tbloom WHERE i2 = 898732 AND i5 = 123451;
                                                        QUERY PLAN
-------------------------------------------------------------------&zwsp;--------------------------------------------------------
 Bitmap Heap Scan on tbloom  (cost=9.29..13.30 rows=1 width=24) (actual time=0.032..0.033 rows=0.00 loops=1)
   Recheck Cond: ((i5 = 123451) AND (i2 = 898732))
   Buffers: shared read=6
   -&gt;  BitmapAnd  (cost=9.29..9.29 rows=1 width=0) (actual time=0.047..0.047 rows=0.00 loops=1)
         Buffers: shared hit=6
         -&gt;  Bitmap Index Scan on btreeidx5  (cost=0.00..4.52 rows=11 width=0) (actual time=0.026..0.026 rows=7.00 loops=1)
               Index Cond: (i5 = 123451)
               Index Searches: 1
               Buffers: shared hit=3
         -&gt;  Bitmap Index Scan on btreeidx2  (cost=0.00..4.52 rows=11