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Re: Scalar in a range (but textual not numeric)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Richard Huxton <dev(at)archonet(dot)com>
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: Scalar in a range (but textual not numeric)
Date: 2004-02-25 22:37:30
Message-ID: 7219.1077748650@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-sql
I wrote:
> try writing
> 	WHERE 'ABCDE' >= pr_min AND 'ABCDE' <= pr_max
> 	      AND pr_min < (SELECT pr_min FROM table
> 			    WHERE pr_min > 'ABCDE'
> 			    ORDER BY pr_min LIMIT 1)
> The idea here is to add an upper bound on pr_min to the index scan
> conditions, so that the scan can stop short of the end of the index.

Argh, got that backwards.  What you are missing is a *lower* bound on
pr_min, and the index scan will therefore run from the start of the
index up to pr_min = 'ABCDE'.  So reverse the sense of the added test:

	      AND pr_min >= (SELECT pr_min FROM table
			     WHERE pr_min <= 'ABCDE'
			     ORDER BY pr_min DESC LIMIT 1)

			regards, tom lane

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