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query plan wierdness?

From: Joel McGraw <jmcgraw(at)eldocomp(dot)com>
To: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: query plan wierdness?
Date: 2004-07-07 21:27:27
Message-ID: 7B3E33EF2A10A84185E3667F6B9A1B781A0679@ECIEXCHANGE.eldocomp.com (view raw or flat)
Thread:
Lists: pgsql-performance
Can someone explain what I'm missing here?   This query does what I
expect--it uses the "foo" index on the openeddatetime, callstatus,
calltype, callkey fields:

elon2=# explain analyse select * from call where aspid='123C' and
OpenedDateTime between '2000-01-01 00:00:00.0' and '2004-06-24
23:59:59.999' order by openeddatetime desc, callstatus desc, calltype
desc, callkey desc limit 26;
 
QUERY PLAN

------------------------------------------------------------------------
------------------------------------------------------------------------
-----------------------------
 Limit  (cost=0.00..103.76 rows=26 width=297) (actual time=0.07..0.58
rows=26 loops=1)
   ->  Index Scan Backward using foo on call  (cost=0.00..1882805.77
rows=471781 width=297) (actual time=0.06..0.54 rows=27 loops=1)
         Index Cond: ((openeddatetime >= '2000-01-01
00:00:00-07'::timestamp with time zone) AND (openeddatetime <=
'2004-06-24 23:59:59.999-07'::timestamp with time zone))
         Filter: (aspid = '123C'::bpchar)
 Total runtime: 0.66 msec
(5 rows)


However, this query performs a sequence scan on the table, ignoring the
call_idx13 index (the only difference is the addition of the aspid field
in the order by clause):

elon2=# explain analyse select * from call where aspid='123C' and
OpenedDateTime between '2000-01-01 00:00:00.0' and '2004-06-24
23:59:59.999' order by aspid, openeddatetime desc, callstatus desc,
calltype desc, callkey desc limit 26;
 
QUERY PLAN

------------------------------------------------------------------------
------------------------------------------------------------------------
------------------------------------------------------------
 Limit  (cost=349379.41..349379.48 rows=26 width=297) (actual
time=32943.52..32943.61 rows=26 loops=1)
   ->  Sort  (cost=349379.41..350558.87 rows=471781 width=297) (actual
time=32943.52..32943.56 rows=27 loops=1)
         Sort Key: aspid, openeddatetime, callstatus, calltype, callkey
         ->  Seq Scan on call  (cost=0.00..31019.36 rows=471781
width=297) (actual time=1.81..7318.13 rows=461973 loops=1)
               Filter: ((aspid = '123C'::bpchar) AND (openeddatetime >=
'2000-01-01 00:00:00-07'::timestamp with time zone) AND (openeddatetime
<= '2004-06-24 23:59:59.999-07'::timestamp with time zone))
 Total runtime: 39353.86 msec
(6 rows)


Here's the structure of the table in question:


                   Table "public.call"
      Column      |           Type           | Modifiers 
------------------+--------------------------+-----------
 aspid            | character(4)             | 
 lastmodifiedtime | timestamp with time zone | 
 moduser          | character(13)            | 
 callkey          | character(13)            | 
 calltype         | text                     | 
 callqueueid      | text                     | 
 openeddatetime   | timestamp with time zone | 
 assigneddatetime | timestamp with time zone | 
 closeddatetime   | timestamp with time zone | 
 reopeneddatetime | timestamp with time zone | 
 openedby         | text                     | 
 callstatus       | character(1)             | 
 callpriority     | text                     | 
 callreasontext   | text                     | 
 keyword1         | text                     | 
 keyword2         | text                     | 
 callername       | text                     | 
 custfirstname    | text                     | 
 custlastname     | text                     | 
 custssntin       | character(9)             |
custssnseq       | text                     | 
 custdbccode      | character(9)             | 
 custlongname     | text                     | 
 custtypecode     | character(2)             | 
 custphone        | text                     | 
 custid           | character(9)             | 
 assigneduserid   | character varying(30)    | 
 historyitemcount | integer                  | 
 callertype       | text                     | 
 callerphoneext   | text                     | 
 followupdate     | text                     | 
 hpjobnumber      | character(11)            | 
Indexes: call_idx1 unique btree (aspid, callkey),
         call_aspid btree (aspid),
         call_aspid_opendedatetime btree (aspid, openeddatetime),
         call_idx10 btree (aspid, keyword1, openeddatetime, callstatus,
calltype
, custtypecode, custid, callkey),
         call_idx11 btree (aspid, keyword2, openeddatetime, callstatus,
calltype
, custtypecode, custid, callkey),
         call_idx12 btree (aspid, custtypecode, custid, openeddatetime,
callstat
us, calltype, callkey),
         call_idx13 btree (aspid, openeddatetime, callstatus, calltype,
callkey),
         call_idx14 btree (aspid, callqueueid, callstatus, callkey),
         call_idx2 btree (aspid, callqueueid, openeddatetime,
custtypecode, call
status, callkey),
         call_idx3 btree (aspid, assigneduserid, openeddatetime,
custtypecode, c
allstatus, callkey),
         call_idx4 btree (aspid, custid, custtypecode, callkey,
callstatus),
         call_idx7 btree (aspid, calltype, custtypecode, custid,
callstatus, cal
lkey),
         call_idx9 btree (aspid, assigneduserid, callstatus,
followupdate),
         foo btree (openeddatetime, callstatus, calltype, callkey)




TIA,

-Joel

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Next:From: Guido BarosioDate: 2004-07-07 21:45:42
Subject: Re: query plan wierdness?
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Subject: Re: [PERFORM] finding a max value

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