Author: jrussell
Date: 2010-11-15 23:05:33 +0100 (Mon, 15 Nov 2010)
New Revision: 23760
Log:
Reduced redundancy and reordered the info in Optimizing Locking Operations.
This section could benefit from further work, but not a top priority.
Modified:
trunk/refman-5.5/optimization.xml
Modified: trunk/refman-5.5/optimization.xml
===================================================================
--- trunk/refman-5.5/optimization.xml 2010-11-15 21:44:45 UTC (rev 23759)
+++ trunk/refman-5.5/optimization.xml 2010-11-15 22:05:33 UTC (rev 23760)
Changed blocks: 3, Lines Added: 62, Lines Deleted: 67; 3871 bytes
@@ -9235,13 +9235,8 @@
<para>
This section discusses internal locking; that is, locking
- performed within the MySQL server itself to manage contention
- for table contents by multiple sessions. This type of locking is
- internal because it is performed entirely by the server and
- involves no other programs. External locking occurs when the
- server and other programs lock table files to coordinate among
- themselves which program can access the tables at which time.
- See <xref linkend="external-locking"/>.
+ performed within the MySQL server to manage contention for table
+ contents by multiple sessions.
</para>
<para>
@@ -9272,6 +9267,66 @@
</para>
<bridgehead>
+ Considerations for Row Locking
+ </bridgehead>
+
+ <para>
+ Advantages of row-level locking:
+ </para>
+
+ <itemizedlist>
+
+ <listitem>
+ <para>
+ Fewer lock conflicts when different sessions access
+ different rows.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Fewer changes for rollbacks.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Possible to lock a single row for a long time.
+ </para>
+ </listitem>
+
+ </itemizedlist>
+
+ <para>
+ Disadvantages of row-level locking:
+ </para>
+
+ <itemizedlist>
+
+ <listitem>
+ <para>
+ Requires more memory than table-level locks.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Slower than table-level locks when used on a large part of
+ the table because you must acquire many more locks.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Slower than other locks if you often do <literal>GROUP
+ BY</literal> operations on a large part of the data or if
+ you must scan the entire table frequently.
+ </para>
+ </listitem>
+
+ </itemizedlist>
+
+ <bridgehead>
Considerations for Table Locking
</bridgehead>
@@ -9421,66 +9476,6 @@
</para>
<bridgehead>
- Considerations for Row Locking
- </bridgehead>
-
- <para>
- Advantages of row-level locking:
- </para>
-
- <itemizedlist>
-
- <listitem>
- <para>
- Fewer lock conflicts when different sessions access
- different rows.
- </para>
- </listitem>
-
- <listitem>
- <para>
- Fewer changes for rollbacks.
- </para>
- </listitem>
-
- <listitem>
- <para>
- Possible to lock a single row for a long time.
- </para>
- </listitem>
-
- </itemizedlist>
-
- <para>
- Disadvantages of row-level locking:
- </para>
-
- <itemizedlist>
-
- <listitem>
- <para>
- Requires more memory than table-level locks.
- </para>
- </listitem>
-
- <listitem>
- <para>
- Slower than table-level locks when used on a large part of
- the table because you must acquire many more locks.
- </para>
- </listitem>
-
- <listitem>
- <para>
- Slower than other locks if you often do <literal>GROUP
- BY</literal> operations on a large part of the data or if
- you must scan the entire table frequently.
- </para>
- </listitem>
-
- </itemizedlist>
-
- <bridgehead>
Choosing the Type of Locking
</bridgehead>
| Thread |
|---|
| • svn commit - mysqldoc@docsrva: r23760 - trunk/refman-5.5 | john.russell | 15 Nov |
