diff options
| -rw-r--r-- | doc/FAQ | 6 | ||||
| -rw-r--r-- | doc/src/FAQ/FAQ.html | 8 |
2 files changed, 7 insertions, 7 deletions
@@ -1,7 +1,7 @@ Frequently Asked Questions (FAQ) for PostgreSQL - Last updated: Wed May 30 18:57:52 EDT 2001 + Last updated: Wed May 30 19:00:33 EDT 2001 Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) @@ -709,9 +709,9 @@ Maximum number of indexes on a table? unlimited column statistics on its own, so VACUUM ANALYZE must be run to collect them periodically. - Indexes are usually not used for ORDER BY or joins: a sequential scan + Indexes are usually not used for ORDER BY or joins. A sequential scan followed by an explicit sort is faster than an indexscan of all tuples - of a large table, because it takes fewer disk accesses. + of a large table. This is because random disk access is very slow. When using wild-card operators such as LIKE or ~, indices can only be used if the beginning of the search is anchored to the start of the diff --git a/doc/src/FAQ/FAQ.html b/doc/src/FAQ/FAQ.html index 932b2b7856d..aba74b0e93a 100644 --- a/doc/src/FAQ/FAQ.html +++ b/doc/src/FAQ/FAQ.html @@ -12,7 +12,7 @@ alink="#0000FF"> <H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1> - <P>Last updated: Wed May 30 18:57:52 EDT 2001</P> + <P>Last updated: Wed May 30 19:00:33 EDT 2001</P> <P>Current maintainer: Bruce Momjian (<A href= "mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR> @@ -908,9 +908,9 @@ Maximum number of indexes on a table? unlimited periodically.</P> <P>Indexes are usually not used for <SMALL>ORDER BY</SMALL> - or joins: a sequential scan followed by an explicit sort is - faster than an indexscan of all tuples of a large table, because it - takes fewer disk accesses.</P> + or joins. A sequential scan followed by an explicit sort is + faster than an indexscan of all tuples of a large table. This + is because random disk access is very slow.</P> <P>When using wild-card operators such as <SMALL>LIKE</SMALL> or <I>~,</I> indices can only be used if the beginning of the search |