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Diffstat (limited to 'doc/src/sgml/runtime.sgml')
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 84 |
1 files changed, 44 insertions, 40 deletions
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index a38e6c0159..71d7f0621c 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 1.235 2004/01/27 16:51:43 neilc Exp $ +$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.236 2004/02/03 17:34:02 tgl Exp $ --> <Chapter Id="runtime"> @@ -850,37 +850,41 @@ SET ENABLE_SEQSCAN TO OFF; </varlistentry> <varlistentry> - <term><varname>sort_mem</varname> (<type>integer</type>)</term> + <term><varname>work_mem</varname> (<type>integer</type>)</term> <listitem> <para> - Specifies the amount of memory to be used by internal sort operations and - hash tables before switching to temporary disk files. The value is + Specifies the amount of memory to be used by internal sort operations + and hash tables before switching to temporary disk files. The value is specified in kilobytes, and defaults to 1024 kilobytes (1 MB). Note that for a complex query, several sort or hash operations might be running in parallel; each one will be allowed to use as much memory as this value specifies before it starts to put data into temporary - files. Also, several running sessions could be doing - sort operations simultaneously. So the total memory used could be many - times the value of <varname>sort_mem</varname>. Sort operations are used - by <literal>ORDER BY</>, merge joins, and <command>CREATE INDEX</>. + files. Also, several running sessions could be doing such operations + concurrently. So the total memory used could be many + times the value of <varname>work_mem</varname>; it is necessary to + keep this fact in mind when choosing the value. Sort operations are + used for <literal>ORDER BY</>, <literal>DISTINCT</>, and + merge joins. Hash tables are used in hash joins, hash-based aggregation, and - hash-based processing of <literal>IN</> subqueries. Because - <command>CREATE INDEX</> is used when restoring a database, - increasing <varname>sort_mem</varname> before doing a large - restore operation can improve performance. + hash-based processing of <literal>IN</> subqueries. </para> </listitem> </varlistentry> <varlistentry> - <term><varname>vacuum_mem</varname> (<type>integer</type>)</term> + <term><varname>maintenance_work_mem</varname> (<type>integer</type>)</term> <listitem> <para> - Specifies the maximum amount of memory to be used by - <command>VACUUM</command> to keep track of to-be-reclaimed - rows. The value is specified in kilobytes, and defaults to - 8192 kB. Larger settings may improve the speed of - vacuuming large tables that have many deleted rows. + Specifies the maximum amount of memory to be used in maintenance + operations, such as <command>VACUUM</command>, <command>CREATE + INDEX</>, and <command>ALTER TABLE ADD FOREIGN KEY</>. + The value is specified in kilobytes, and defaults to 16384 kilobytes + (16 MB). Since only one of these operations can be executed at + a time by a database session, and an installation normally doesn't + have very many of them happening concurrently, it's safe to set this + value significantly larger than <varname>work_mem</varname>. Larger + settings may improve performance for vacuuming and for restoring + database dumps. </para> </listitem> </varlistentry> @@ -1412,25 +1416,25 @@ SET ENABLE_SEQSCAN TO OFF; <para> Various tuning parameters for the genetic query optimization algorithm. The recommended one to modify is - <varname>geqo_effort</varname>, which can range from 1 to 10 with - a default of 5. Larger values increase the time spent in planning - but make it more likely that a good plan will be found. - <varname>geqo_effort</varname> doesn't actually do anything directly, - it is just used to compute the default values for the other - parameters. If you prefer, you can set the other parameters by hand - instead. - The pool size is the number of individuals in the genetic population. - It must be at least two, and useful values are typically 100 to 1000. - If it is set to zero (the default setting) then a suitable default - is chosen based on <varname>geqo_effort</varname> and the number of - tables in the query. - Generations specifies the number of iterations of the algorithm. - It must be at least one, and useful values are in the same range - as the pool size. - If it is set to zero (the default setting) then a suitable default - is chosen based on the pool size. - The run time of the algorithm is roughly proportional to the sum of - pool size and generations. + <varname>geqo_effort</varname>, which can range from 1 to 10 with + a default of 5. Larger values increase the time spent in planning + but make it more likely that a good plan will be found. + <varname>geqo_effort</varname> doesn't actually do anything directly, + it is just used to compute the default values for the other + parameters. If you prefer, you can set the other parameters by hand + instead. + The pool size is the number of individuals in the genetic population. + It must be at least two, and useful values are typically 100 to 1000. + If it is set to zero (the default setting) then a suitable default + is chosen based on <varname>geqo_effort</varname> and the number of + tables in the query. + Generations specifies the number of iterations of the algorithm. + It must be at least one, and useful values are in the same range + as the pool size. + If it is set to zero (the default setting) then a suitable default + is chosen based on the pool size. + The run time of the algorithm is roughly proportional to the sum of + pool size and generations. The selection bias is the selective pressure within the population. Values can be from 1.50 to 2.00; the latter is the default. @@ -2840,7 +2844,7 @@ $ <userinput>postmaster -o '-S 1024 -s'</userinput> <row> <entry><option>-S <replaceable>x</replaceable></option><footnoteref linkend="fn.runtime-config-short"> </entry> - <entry><literal>sort_mem = <replaceable>x</replaceable></></entry> + <entry><literal>work_mem = <replaceable>x</replaceable></></entry> </row> <row> @@ -3230,7 +3234,7 @@ kernel.shmmax = 134217728 <para> In OS X 10.2 and earlier, edit the file <filename>/System/Library/StartupItems/SystemTuning/SystemTuning</> - and change the values in the following commands: + and change the values in the following commands: <programlisting> sysctl -w kern.sysv.shmmax sysctl -w kern.sysv.shmmin @@ -3239,7 +3243,7 @@ sysctl -w kern.sysv.shmseg sysctl -w kern.sysv.shmall </programlisting> In OS X 10.3, these commands have been moved to <filename>/etc/rc</> - and must be edited there. + and must be edited there. </para> </listitem> </varlistentry> |