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Diffstat (limited to 'doc/FAQ')
| -rw-r--r-- | doc/FAQ | 23 |
1 files changed, 8 insertions, 15 deletions
@@ -1,7 +1,7 @@ Frequently Asked Questions (FAQ) for PostgreSQL - Last updated: Mon Jan 31 19:18:44 EST 2005 + Last updated: Mon Jan 31 20:35:58 EST 2005 Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) @@ -445,17 +445,13 @@ PostgreSQL releases? The PostgreSQL team makes only small changes between minor releases, - so upgrading from 7.2 to 7.2.1 does not require a dump and restore. - However, major releases (e.g. from 7.2 to 7.3) often change the + so upgrading from 7.4 to 7.4.1 does not require a dump and restore. + However, major releases (e.g. from 7.3 to 7.4) often change the internal format of system tables and data files. These changes are - often complex, so we don't maintain backward compatability for data + often complex, so we don't maintain backward compatibility for data files. A dump outputs data in a generic format that can then be loaded in using the new internal format. - In releases where the on-disk format does not change, the pg_upgrade - script can be used to upgrade without a dump/restore. The release - notes mention whether pg_upgrade is available for the release. - 3.8) What computer hardware should I use? Because PC hardware is mostly compatible, people tend to believe that @@ -471,13 +467,10 @@ 4.1) How do I SELECT only the first few rows of a query? A random row? - See the FETCH manual page, or use SELECT ... LIMIT.... - - The entire query may have to be evaluated, even if you only want the - first few rows. Consider using a query that has an ORDER BY. If there - is an index that matches the ORDER BY, PostgreSQL may be able to - evaluate only the first few records requested, or the entire query may - have to be evaluated until the desired rows have been generated. + To retrieve only a few rows, if you know at the number of rows needed + at the time of the SELECT use LIMIT . If an index matches the ORDER BY + it is possible the entire query does not have to be executed. If you + don't know the number of rows at SELECT time, use a cursor and FETCH. To SELECT a random row, use: SELECT col |