From d86d51a95810caebcea587498068ff32fe28293e Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 5 Jan 2010 21:54:00 +0000
Subject: Support ALTER TABLESPACE name SET/RESET ( tablespace_options ).

This patch only supports seq_page_cost and random_page_cost as parameters,
but it provides the infrastructure to scalably support many more.
In particular, we may want to add support for effective_io_concurrency,
but I'm leaving that as future work for now.

Thanks to Tom Lane for design help and Alvaro Herrera for the review.
---
 doc/src/sgml/config.sgml               | 11 ++++++++++-
 doc/src/sgml/ref/alter_tablespace.sgml | 22 +++++++++++++++++++++-
 2 files changed, 31 insertions(+), 2 deletions(-)

(limited to 'doc/src')

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index df8f858c545..34f472555e5 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.241 2009/12/25 01:09:31 rhaas Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.242 2010/01/05 21:53:58 rhaas Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -2000,6 +2000,9 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"'  # Windows
        <para>
         Sets the planner's estimate of the cost of a disk page fetch
         that is part of a series of sequential fetches.  The default is 1.0.
+        This value can be overriden for a particular tablespace by setting
+        the tablespace parameter of the same name
+        (see <xref linkend="sql-altertablespace">).
        </para>
       </listitem>
      </varlistentry>
@@ -2013,6 +2016,12 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"'  # Windows
        <para>
         Sets the planner's estimate of the cost of a
         non-sequentially-fetched disk page.  The default is 4.0.
+        This value can be overriden for a particular tablespace by setting
+        the tablespace parameter of the same name
+        (see <xref linkend="sql-altertablespace">).
+       </para>
+
+	   <para>
         Reducing this value relative to <varname>seq_page_cost</>
         will cause the system to prefer index scans; raising it will
         make index scans look relatively more expensive.  You can raise
diff --git a/doc/src/sgml/ref/alter_tablespace.sgml b/doc/src/sgml/ref/alter_tablespace.sgml
index 8c5341dd084..758ee13aa69 100644
--- a/doc/src/sgml/ref/alter_tablespace.sgml
+++ b/doc/src/sgml/ref/alter_tablespace.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_tablespace.sgml,v 1.5 2009/09/19 10:23:26 petere Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_tablespace.sgml,v 1.6 2010/01/05 21:53:58 rhaas Exp $
 PostgreSQL documentation
 -->
 
@@ -23,6 +23,8 @@ PostgreSQL documentation
 <synopsis>
 ALTER TABLESPACE <replaceable>name</replaceable> RENAME TO <replaceable>new_name</replaceable>
 ALTER TABLESPACE <replaceable>name</replaceable> OWNER TO <replaceable>new_owner</replaceable>
+ALTER TABLESPACE <replaceable>name</replaceable> SET ( <replaceable class="PARAMETER">tablespace_option</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )
+ALTER TABLESPACE <replaceable>name</replaceable> RESET ( <replaceable class="PARAMETER">tablespace_option</replaceable> [, ... ] )
 </synopsis>
  </refsynopsisdiv>
   
@@ -74,6 +76,24 @@ ALTER TABLESPACE <replaceable>name</replaceable> OWNER TO <replaceable>new_owner
      </para>
     </listitem>
    </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">tablespace_parameter</replaceable></term>
+    <listitem>
+     <para>
+      A tablespace parameter to be set or reset.  Currently, the only
+      available parameters are <varname>seq_page_cost</> and
+      <varname>random_page_cost</>.  Setting either value for a particular
+      tablespace will override the planner's usual estimate of the cost of
+      reading pages from tables in that tablespace, as established by
+      the configuration parameters of the same name (see
+      <xref linkend="guc-seq-page-cost">,
+      <xref linkend="guc-random-page-cost">).  This may be useful if one
+      tablespace is located on a disk which is faster or slower than the
+      remainder of the I/O subsystem.
+     </para>
+    </listitem>
+   </varlistentry>
   </variablelist>
  </refsect1>
 
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