use this
explain analyze select * from result where active = 't';
--- On Thu, 6/26/08, Phillip Mills <[EMAIL PROTECTED]> wrote:
From: Phillip Mills <[EMAIL PROTECTED]>
Subject: [GENERAL] Partial Index Too Literal?
To: pgsql-general@postgresql.org
Date: Thursday, June 26, 2008, 7:24 PM
Under somewhat unusual circumstances, rows in one of our tables have an
'active' flag with a true value. We check for these relatively often since
they represent cases that need special handling. We've found through testing
that having a partial index on that field works well. What seems odd to me,
however, is that the index gets used only if the query is a textual match for
how the index was specified.
That is, using an index defined as 'where active = true':
dev=# explain analyze select * from result where active = true;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on result (cost=5.31..472.34 rows=4206 width=1126) (actual
time=7.868..7.868 rows=0 loops=1)
Filter: active
-> Bitmap Index Scan on result_active_idx (cost=0.00..4.26 rows=2103
width=0) (actual time=4.138..4.138 rows=16625 loops=1)
Index Cond: (active = true)
Total runtime: 7.918 ms
(5 rows)
dev=# explain analyze select * from result where active is true;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------
Seq Scan on result (cost=0.00..537.26 rows=4263 width=1126) (actual
time=55.631..55.631 rows=0 loops=1)
Filter: (active IS TRUE)
Total runtime: 55.668 ms
(3 rows)
This is version 8.2.6. Is there something I'm missing that could make these
queries ever produce different results?
