svn commit - mysqldoc@oter02: r25795 - in trunk: . dynamic-docs/changelog refman-5.6

[paul.dubois]

Author: pd221994
Date: 2011-04-08 00:19:25 +0200 (Fri, 08 Apr 2011)
New Revision: 25795

Log:
 r46840@dhcp-adc-twvpn-1-vpnpool-10-154-11-3:  paul | 2011-04-07 17:18:20 -0500
 Fix changelog entry version


Modified:
   svk:merge
   trunk/dynamic-docs/changelog/mysqld-2.xml
   trunk/refman-5.6/optimization.xml

Property changes on: trunk
___________________________________________________________________

Modified: svk:merge
===================================================================


Changed blocks: 0, Lines Added: 0, Lines Deleted: 0; 1277 bytes


Modified: trunk/dynamic-docs/changelog/mysqld-2.xml
===================================================================
--- trunk/dynamic-docs/changelog/mysqld-2.xml	2011-04-07 22:19:04 UTC (rev 25794)
+++ trunk/dynamic-docs/changelog/mysqld-2.xml	2011-04-07 22:19:25 UTC (rev 25795)
Changed blocks: 1, Lines Added: 1, Lines Deleted: 1; 420 bytes

@@ -43540,7 +43540,7 @@
     </bugs>
 
     <versions>
-      <version ver="5.6.1"/>
+      <version ver="5.6.2"/>
     </versions>
 
     <message>


Modified: trunk/refman-5.6/optimization.xml
===================================================================
--- trunk/refman-5.6/optimization.xml	2011-04-07 22:19:04 UTC (rev 25794)
+++ trunk/refman-5.6/optimization.xml	2011-04-07 22:19:25 UTC (rev 25795)
Changed blocks: 2, Lines Added: 35, Lines Deleted: 7; 3264 bytes

@@ -17755,17 +17755,31 @@
       <title>Index Condition Pushdown Optimization</title>
 
       <para>
+        Index Condition Pushdown (ICP) is an optimization for the case
+        where MySQL retrieves rows from a table using an index. Without
+        ICP, the storage engine traverses the index to locate rows in
+        the base table and returns them to the MySQL server which
+        evaluates the <literal>WHERE</literal> condition for the rows.
+        With ICP enabled, and if parts of the <literal>WHERE</literal>
+        condition can be evaluated by using only fields from the index,
+        the MySQL server pushes this part of the
+        <literal>WHERE</literal> condition down to the storage engine.
+        The storage engine then evaluates the pushed index condition by
+        using the index entry and only if this is satisfied is base row
+        be read. ICP can reduce the number of accesses the storage
+        engine has to do against the base table and the number of
+        accesses the MySQL server has to do against the storage engine.
+      </para>
+
+      <para>
         Index Condition Pushdown optimization is used for the
         <literal role="jointype">range</literal>,
         <literal role="jointype">ref</literal>,
         <literal role="jointype">eq_ref</literal>, and
         <literal role="jointype">ref_or_null</literal> access methods
-        when there is a need to access full table rows. The optimization
-        is that the server tries to use index information to defer
-        (<quote>push down</quote>) reading of full table rows unless it
-        is known to be necessary. This is done by performing early tests
-        on index tuples first. This strategy can be used for
-        <literal>InnoDB</literal> and <literal>MyISAM</literal> tables.
+        when there is a need to access full table rows. This strategy
+        can be used for <literal>InnoDB</literal> and
+        <literal>MyISAM</literal> tables.
       </para>
 
       <para>

@@ -19268,9 +19282,23 @@
       </indexterm>
 
       <para>
-        The Multi-Range Read (MRR) optimization provides these benefits:
+        Reading rows using a range scan on a secondary index can result
+        in many random disk accesses to the base table when the table is
+        large and not stored in the storage engine's cache. With the
+        Disk-Sweep Multi-Range Read (MRR) optimization, MySQL tries to
+        reduce the number of random disk access for range scans by first
+        scanning the index only and collecting the keys for the relevant
+        rows. Then the keys are sorted and finally the rows are
+        retrieved from the base table using the order of the primary
+        key. The motivation for Disk-sweep MRR is to reduce the number
+        of random disk accesses and instead achieve a more sequential
+        scan of the base table data.
       </para>
 
+      <para>
+        The Multi-Range Read optimization provides these benefits:
+      </para>
+
       <itemizedlist>
 
         <listitem>