diff --git a/doc/FAQ b/doc/FAQ index f59d74ff9a3..7224c15f775 100644 --- a/doc/FAQ +++ b/doc/FAQ @@ -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">

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)
@@ -908,9 +908,9 @@ Maximum number of indexes on a table? unlimited periodically.

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.

+ 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.

When using wild-card operators such as LIKE or ~, indices can only be used if the beginning of the search