diff options
| author | Bruce Momjian | 2006-02-24 14:59:54 +0000 |
|---|---|---|
| committer | Bruce Momjian | 2006-02-24 14:59:54 +0000 |
| commit | 0915d370f549e68ec56cf819d0023bb2c237603d (patch) | |
| tree | a4488b188940a85142e7c7c2b468320062e09a43 | |
| parent | eb8f9cc066dd0c9642a6101a833b6e0d698c2a6b (diff) | |
Remove mention of MIN/MAX() not using indexes.
| -rw-r--r-- | doc/FAQ | 12 | ||||
| -rw-r--r-- | doc/src/FAQ/FAQ.html | 14 |
2 files changed, 6 insertions, 20 deletions
@@ -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 ([email protected]) @@ -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. diff --git a/doc/src/FAQ/FAQ.html b/doc/src/FAQ/FAQ.html index 3c10b91607a..7359ba271dc 100644 --- a/doc/src/FAQ/FAQ.html +++ b/doc/src/FAQ/FAQ.html @@ -10,7 +10,7 @@ alink="#0000ff"> <H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1> - <P>Last updated: Sun Feb 12 12:15:49 EST 2006</P> + <P>Last updated: Fri Feb 24 09:59:35 EST 2006</P> <P>Current maintainer: Bruce Momjian (<A href= "mailto:[email protected]">[email protected]</A>) @@ -742,16 +742,8 @@ table?</TD><TD>unlimited</TD></TR> usually faster than an index scan of a large table.</P> However, <SMALL>LIMIT</SMALL> combined with <SMALL>ORDER BY</SMALL> 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: -<PRE> - SELECT col - FROM tab - ORDER BY col [ DESC ] - LIMIT 1; -</PRE> - + is returned.</P> + <P>If you believe the optimizer is incorrect in choosing a sequential scan, use <CODE>SET enable_seqscan TO 'off'</CODE> and run query again to see if an index scan is indeed faster.</P> |