Re: non index use on LIKE on a non pattern string

=?iso-8859-1?q?C=E9dric_Villemain?= <cedric(at)2ndquadrant(dot)com> writes:
>> I have noticed that with a SELECT query containing the following
>> constraint:
>>
>> column LIKE ?
>>
>> and an index on that column, PostgreSQL will not use the index
>> even if the parameter doesn't contain special pattern characters
>> such as %.

> you should have a postgresql 8.3,isn't it ?
> like is equal to "=" in your case, since 8.4

No, the planner has understood about wildcard-free LIKE patterns
producing an "=" index condition at least since 7.3. I think what the
OP is complaining about is the problem that the pattern has to be
actually constant (ie, NOT a parameter) before it can be optimized into
an index condition. This should be better in 9.2 ...

regards, tom lane