avoid recasting text to tsvector when calculating selectivity

From: Jan Urbański <j(dot)urbanski(at)students(dot)mimuw(dot)edu(dot)pl>
To: Postgres - Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: avoid recasting text to tsvector when calculating selectivity
Date: 2008-07-16 20:56:55
Message-ID: 487E6097.2040707@students.mimuw.edu.pl
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I'm about to write a oprrest function for the @@ operator. Currently @@
handles multiple cases, like tsvector @@ tsquery, text @@ tsquery,
tsquery @@ tsvector etc. The text @@ text case is for instance handled
by calling to_tsvector and plainto_tsquery on the input arguments.

For a @@ restriction function, I need to have a tsquery and a tsvector,
so in the text @@ text situation I'd end up calling plainto_tsquery
during planning, which would consequently get called again during
execution. Also, I'd need a not-so-elegant if-elsif-elsif sequence at
the beginning of the function. Is this OK/unavoidable/easly avoided?

Cheers,
Jan
--
Jan Urbanski
GPG key ID: E583D7D2

ouden estin

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