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Postgres FD Implementation
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Abuhujair Javed
Postgres FD Implementation
Commits
3b6afdd7
Commit
3b6afdd7
authored
May 11, 2007
by
Neil Conway
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Improvements to the SGML docs for TRUNCATE and CLUSTER.
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bc8036fc
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doc/src/sgml/ref/cluster.sgml
doc/src/sgml/ref/cluster.sgml
+2
-2
doc/src/sgml/ref/truncate.sgml
doc/src/sgml/ref/truncate.sgml
+32
-29
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doc/src/sgml/ref/cluster.sgml
View file @
3b6afdd7
<!--
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/cluster.sgml,v 1.4
2 2007/04/08 02:07:35 tgl
Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/cluster.sgml,v 1.4
3 2007/05/11 19:40:07 neilc
Exp $
PostgreSQL documentation
PostgreSQL documentation
-->
-->
...
@@ -45,7 +45,7 @@ CLUSTER
...
@@ -45,7 +45,7 @@ CLUSTER
not clustered. That is, no attempt is made to store new or
not clustered. That is, no attempt is made to store new or
updated rows according to their index order. (If one wishes, one can
updated rows according to their index order. (If one wishes, one can
periodically recluster by issuing the command again. Also, setting
periodically recluster by issuing the command again. Also, setting
the table's
FILLFACTOR
storage parameter to less than 100% can aid
the table's
<literal>FILLFACTOR</literal>
storage parameter to less than 100% can aid
in preserving cluster ordering during updates, since updated rows
in preserving cluster ordering during updates, since updated rows
are preferentially kept on the same page.)
are preferentially kept on the same page.)
</para>
</para>
...
...
doc/src/sgml/ref/truncate.sgml
View file @
3b6afdd7
<!--
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/truncate.sgml,v 1.2
3 2007/04/07 17:12:15 tgl
Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/truncate.sgml,v 1.2
4 2007/05/11 19:40:08 neilc
Exp $
PostgreSQL documentation
PostgreSQL documentation
-->
-->
...
@@ -31,9 +31,9 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
...
@@ -31,9 +31,9 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
<command>TRUNCATE</command> quickly removes all rows from a set of
<command>TRUNCATE</command> quickly removes all rows from a set of
tables. It has the same effect as an unqualified
tables. It has the same effect as an unqualified
<command>DELETE</command> on each table, but since it does not actually
<command>DELETE</command> on each table, but since it does not actually
scan the tables it is faster
; furthermore
it reclaims disk space
scan the tables it is faster
. Furthermore,
it reclaims disk space
immediately, rather than requiring a subsequent
vacuum operation.
immediately, rather than requiring a subsequent
<command>VACUUM</command>
This is most useful on large tables.
operation.
This is most useful on large tables.
</para>
</para>
</refsect1>
</refsect1>
...
@@ -86,35 +86,38 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
...
@@ -86,35 +86,38 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
in the same command. Checking validity in such cases would require table
in the same command. Checking validity in such cases would require table
scans, and the whole point is not to do one. The <literal>CASCADE</>
scans, and the whole point is not to do one. The <literal>CASCADE</>
option can be used to automatically include all dependent tables —
option can be used to automatically include all dependent tables —
but be very careful when using this option, else you might lose data you
but be very careful when using this option,
or
else you might lose data you
did not intend to!
did not intend to!
</para>
</para>
<para>
<para>
<command>TRUNCATE</> will not run any
user-defined <literal>ON
<command>TRUNCATE</> will not run any
<literal>ON DELETE</literal>
DELETE</literal>
triggers that might exist for the tables.
triggers that might exist for the tables.
</para>
</para>
<para>
<warning>
<command>TRUNCATE</> is not MVCC-safe (see <xref linkend="mvcc">
<para>
for general information about MVCC). After truncation, the table
<command>TRUNCATE</> is not MVCC-safe (see <xref linkend="mvcc">
will appear empty to all concurrent transactions, even if they are
for general information about MVCC). After truncation, the table
using a snapshot taken before the truncation occurred. This will
will appear empty to all concurrent transactions, even if they
only be an issue for a transaction that did not touch the table
are using a snapshot taken before the truncation occurred. This
before the truncation started — any transaction that has done
will only be an issue for a transaction that did not access the
so would hold at least <literal>ACCESS SHARE</literal> lock,
truncated table before the truncation happened — any
which would block
transaction that has done so would hold at least an
<command>TRUNCATE</> until that transaction completes. So
<literal>ACCESS SHARE</literal> lock, which would block
truncation will not cause any apparent inconsistency in the table
<command>TRUNCATE</> until that transaction completes. So
contents for successive queries on the same table, but it could
truncation will not cause any apparent inconsistency in the table
cause visible inconsistency between the contents of the
contents for successive queries on the same table, but it could
truncated table and other tables.
cause visible inconsistency between the contents of the truncated
</para>
table and other tables in the database.
</para>
<para>
<command>TRUNCATE</> is transaction-safe, however: the truncation
<para>
will roll back if the surrounding transaction does not commit.
<command>TRUNCATE</> is transaction-safe, however: the truncation
</para>
will be safely rolled back if the surrounding transaction does not
commit.
</para>
</warning>
</refsect1>
</refsect1>
<refsect1>
<refsect1>
...
@@ -124,13 +127,13 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
...
@@ -124,13 +127,13 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
Truncate the tables <literal>bigtable</literal> and <literal>fattable</literal>:
Truncate the tables <literal>bigtable</literal> and <literal>fattable</literal>:
<programlisting>
<programlisting>
TRUNCATE
TABLE
bigtable, fattable;
TRUNCATE bigtable, fattable;
</programlisting>
</programlisting>
</para>
</para>
<para>
<para>
Truncate the table <literal>othertable</literal>, and cascade to any tables
Truncate the table <literal>othertable</literal>, and cascade to any tables
that
are referencing
<literal>othertable</literal> via foreign-key
that
reference
<literal>othertable</literal> via foreign-key
constraints:
constraints:
<programlisting>
<programlisting>
...
...
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