index scan with functional indexes - Mailing list pgsql-hackers

From Dave Cramer
Subject index scan with functional indexes
Date
Msg-id 1075213610.1611.287.camel@localhost.localdomain
Whole thread Raw
In response to Re: returning PGresult as xml  (Andrew Dunstan <andrew@dunslane.net>)
Responses Re: index scan with functional indexes  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
I'm curious what the result of a reverse index does on a table with url
like data, so I did the following


create function fn_strrev(text) returns text as 'return reverse($_[0])'
language 'plperl' with (iscachable);

create index r_url_idx on url( fn_strrev(url));

vacuum analyze;


explain select * from url where url like fn_strrev('%beta12.html');                      QUERY PLAN
---------------------------------------------------------Seq Scan on url  (cost=0.00..13281.70 rows=1 width=454)
Filter:((url)::text ~~ 'lmth.21ateb%'::text)
 


Is it possible to get the planner to use an index scan ?

How?

the db is using locale 'C'

-- 
Dave Cramer
519 939 0336
ICQ # 1467551



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