Fwd: Bad query performance with more conditions?

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On Thu, Jun 24, 2010 at 16:57, Thom Brown <thombrown(at)gmail(dot)com> wrote:
> Sounds like the planner took a wrong turn in the 2nd case.  Which
> version of PostgreSQL are you running?

PostgreSQL version 8.1.21 (With schemas)

The explain commands show that:

db1=> explain select * from emails where email_msg_id =
'4dba381b-f55e-02d3-4b4a-95e2e98178e2' limit 1;
                                                     QUERY PLAN
-------------------------------------------------------------------------------------------------------------------
Limit  (cost=0.00..4.00 rows=1 width=184)
  ->  Index Scan using idx_emails_email_msg_id on emails
(cost=0.00..370016.42 rows=92413 width=184)
        Index Cond: (email_msg_id =
'4dba381b-f55e-02d3-4b4a-95e2e98178e2'::bpchar)
(3 rows)

db1=> explain select * from emails where email_msg_id =
'4dba381b-f55e-02d3-4b4a-95e2e98178e2' and email_sender =
'sender(at)domain(dot)com' limit 1;

   QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.00..801.06 rows=1 width=184)
  ->  Index Scan using idx_emails_email_sender on emails
(cost=0.00..370089.46 rows=462 width=184)
        Index Cond: (email_sender = 'sender(at)domain(dot)com'::text)
        Filter: (email_msg_id = '4dba381b-f55e-02d3-4b4a-95e2e98178e2'::bpchar)
(4 rows)