diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ref/reindex.sgml | 30 | ||||
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 31 |
2 files changed, 42 insertions, 19 deletions
diff --git a/doc/src/sgml/ref/reindex.sgml b/doc/src/sgml/ref/reindex.sgml index 98b6e3b69d9..13bb9f5098c 100644 --- a/doc/src/sgml/ref/reindex.sgml +++ b/doc/src/sgml/ref/reindex.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/ref/reindex.sgml,v 1.24 2004/10/24 22:52:04 tgl Exp $ +$PostgreSQL: pgsql/doc/src/sgml/ref/reindex.sgml,v 1.25 2004/11/04 19:08:08 tgl Exp $ PostgreSQL documentation --> @@ -29,7 +29,7 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac <para> <command>REINDEX</command> rebuilds an index based on the data - stored in the table, replacing the old copy of the index. There are + stored in the index's table, replacing the old copy of the index. There are two main reasons to use <command>REINDEX</command>: <itemizedlist> @@ -98,6 +98,8 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac <para> The name of the specific database, table, or index to be reindexed. Table and index names may be schema-qualified. + Presently, <command>REINDEX DATABASE</> can only reindex the current + database, so its parameter must match the current database's name. </para> </listitem> </varlistentry> @@ -119,13 +121,7 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac <para> If you suspect corruption of an index on a user table, you can simply rebuild that index, or all indexes on the table, using - <command>REINDEX INDEX</command> or <command>REINDEX - TABLE</command>. Another approach to dealing with a corrupted - user-table index is just to drop and recreate it. This may in fact - be preferable if you would like to maintain some semblance of - normal operation on the table meanwhile. <command>REINDEX</> - acquires exclusive lock on the table, while <command>CREATE - INDEX</> only locks out writes not reads of the table. + <command>REINDEX INDEX</command> or <command>REINDEX TABLE</command>. </para> <para> @@ -188,6 +184,22 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac </para> <para> + <command>REINDEX</command> is similar to a drop and recreate of the index + in that the index contents are rebuilt from scratch. However, the locking + considerations are rather different. <command>REINDEX</> locks out writes + but not reads of the index's parent table. It also takes an exclusive lock + on the specific index being processed, which will block reads that attempt + to use that index. In contrast, <command>DROP INDEX</> momentarily takes + exclusive lock on the parent table, blocking both writes and reads. The + subsequent <command>CREATE INDEX</> locks out writes but not reads; since + the index is not there, no read will attempt to use it, meaning that there + will be no blocking but reads may be forced into expensive sequential + scans. Another important point is that the drop/create approach + invalidates any cached query plans that use the index, while + <command>REINDEX</> does not. + </para> + + <para> Prior to <productname>PostgreSQL</productname> 7.4, <command>REINDEX TABLE</> did not automatically process TOAST tables, and so those had to be reindexed by separate commands. This is still possible, but diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index b4a84616f54..be2ced298d3 100644 --- a/doc/src/sgml/runtime.sgml +++ b/doc/src/sgml/runtime.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.289 2004/10/17 22:01:49 tgl Exp $ +$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.290 2004/11/04 19:08:30 tgl Exp $ --> <Chapter Id="runtime"> @@ -583,7 +583,7 @@ SET ENABLE_SEQSCAN TO OFF; <listitem> <para> Specifies the main server configuration file - (customarily called <filename>postgresql.conf</>). + (customarily called <filename>postgresql.conf</>). This option can only be set on the postmaster command line. </para> </listitem> @@ -615,8 +615,8 @@ SET ENABLE_SEQSCAN TO OFF; <listitem> <para> Specifies that the <application>postmaster</> should create an - additional process-id (PID) file for use by server administration - programs. + additional process-id (PID) file for use by server administration + programs. This option can only be set at server start. </para> </listitem> @@ -1666,9 +1666,20 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32 <listitem> <para> Sets the planner's assumption about the effective size of the - disk cache (that is, the portion of the kernel's disk cache - that will be used for <productname>PostgreSQL</productname> - data files). This is measured in disk pages, which are + disk cache that is available to a single index scan. This is + factored into estimates of the cost of using an index; a higher + value makes it more likely index scans will be used, a lower + value makes it more likely sequential scans will be used. When + setting this parameter you should consider both + <productname>PostgreSQL</productname>'s shared buffers and the + portion of the kernel's disk cache that will be used for + <productname>PostgreSQL</productname> data files. Also, take into + account the expected number of concurrent queries using different + indexes, since they will have to share the available space. + This parameter has no effect on the size of shared memory + allocated by PostgreSQL, nor does it reserve kernel disk cache; + it is used only for estimation purposes. + The value is measured in disk pages, which are normally 8192 bytes each. The default is 1000. </para> </listitem> @@ -1678,7 +1689,7 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32 <term><varname>random_page_cost</varname> (<type>floating point</type>)</term> <listitem> <para> - Sets the query planner's estimate of the cost of a + Sets the planner's estimate of the cost of a nonsequentially fetched disk page. This is measured as a multiple of the cost of a sequential page fetch. A higher value makes it more likely a sequential scan will be used, a @@ -1692,7 +1703,7 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32 <term><varname>cpu_tuple_cost</varname> (<type>floating point</type>)</term> <listitem> <para> - Sets the query planner's estimate of the cost of processing + Sets the planner's estimate of the cost of processing each row during a query. This is measured as a fraction of the cost of a sequential page fetch. The default is 0.01. </para> @@ -1703,7 +1714,7 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32 <term><varname>cpu_index_tuple_cost</varname> (<type>floating point</type>)</term> <listitem> <para> - Sets the query planner's estimate of the cost of processing + Sets the planner's estimate of the cost of processing each index row during an index scan. This is measured as a fraction of the cost of a sequential page fetch. The default is 0.001. |