Minor documentation updates from Simon Riggs.

doc/src/sgml/ref/reindex.sgml

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-$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>
@@ -187,6 +183,22 @@ REINDEX { DATABASE | TABLE | INDEX } <replaceable class="PARAMETER">name</replac
    a btree</> errors.)
   </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

doc/src/sgml/runtime.sgml

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-$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 $
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 <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.

src/backend/utils/misc/guc.c

@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.246 2004/10/22 19:48:19 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.247 2004/11/04 19:08:42 tgl Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -1344,7 +1344,7 @@ static struct config_real ConfigureNamesReal[] =
 						 "pages, which are normally 8 kB each.")
 		},
 		&effective_cache_size,
-		DEFAULT_EFFECTIVE_CACHE_SIZE, 0, DBL_MAX, NULL, NULL
+		DEFAULT_EFFECTIVE_CACHE_SIZE, 1, DBL_MAX, NULL, NULL
 	},
 	{
 		{"random_page_cost", PGC_USERSET, QUERY_TUNING_COST,