From: Bruce Momjian <maillist@candle.pha.pa.us>
Message-Id: <199906100051.UAA14533@candle.pha.pa.us>
Subject: Re: [HACKERS] Postgres 6.5 beta2 and beta3 problem
In-Reply-To: <29420.928948234@sss.pgh.pa.us> from Tom Lane at "Jun 9,
	1999 01:10:34 pm"
To: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 9 Jun 1999 20:51:04 -0400 (EDT)
CC: Daniel Kalchev <daniel@digsys.bg>, pgsql-hackers@postgreSQL.org
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> LIKE doesn't know anything about indexes, nor vice versa.  What the
> index-scan machinery *does* know about is <, <=, etc.  If you have
> WHERE clauses like "x >= 33" and "x <= 54" then an index scan knows
> to only scan the part of the index from 33 to 54.  So you never even
> visit a large fraction of the table.  This is why an index scan can
> be faster than a sequential scan even though the per-tuple overhead
> of consulting the index is larger.
> 

You know, everyone beats me up for that LIKE indexing hack, but every
month that goes by where someone does not come up with a better solution
makes me feel a little better about the criticism.

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
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