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Backpatch FAQ changes to 8.1.X.

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Bruce Momjian
2006-02-24 15:00:48 +00:00
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@ -1,7 +1,7 @@
Frequently Asked Questions (FAQ) for PostgreSQL
Last updated: Sun Feb 12 12:15:49 EST 2006
Last updated: Fri Feb 24 09:59:35 EST 2006
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
@ -569,14 +569,8 @@
sequential scan followed by an explicit sort is usually faster than an
index scan of a large table.
However, LIMIT combined with ORDER BY often will use an index because
only a small portion of the table is returned. In fact, though MAX()
and MIN() don't use indexes, it is possible to retrieve such values
using an index with ORDER BY and LIMIT:
SELECT col
FROM tab
ORDER BY col [ DESC ]
LIMIT 1;
only a small portion of the table is returned.
If you believe the optimizer is incorrect in choosing a sequential
scan, use SET enable_seqscan TO 'off' and run query again to see if an
index scan is indeed faster.