|
1 | 1 | <!-- |
2 | | -$PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.51 2005/11/04 23:14:00 petere Exp $ |
| 2 | +$PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.52 2005/12/07 05:35:53 momjian Exp $ |
3 | 3 | --> |
4 | 4 |
|
5 | 5 | <chapter id="maintenance"> |
@@ -141,11 +141,12 @@ $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.51 2005/11/04 23:14:00 pete |
141 | 141 | command. The first form, known as <quote>lazy vacuum</quote> or |
142 | 142 | just <command>VACUUM</command>, marks expired data in tables and |
143 | 143 | indexes for future reuse; it does <emphasis>not</emphasis> attempt |
144 | | - to reclaim the space used by this expired data |
145 | | - immediately. Therefore, the table file is not shortened, and any |
146 | | - unused space in the file is not returned to the operating |
147 | | - system. This variant of <command>VACUUM</command> can be run |
148 | | - concurrently with normal database operations. |
| 144 | + to reclaim the space used by this expired data unless the space is |
| 145 | + at the end of the table and an exclusive lock can be obtained easily |
| 146 | + on the table. Unused space at the start or middle of the file does |
| 147 | + not result in the file being shortened and space returned to the |
| 148 | + operating system. This variant of <command>VACUUM</command> can be |
| 149 | + run concurrently with normal database operations. |
149 | 150 | </para> |
150 | 151 |
|
151 | 152 | <para> |
|