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Jakob Huber
postgres-lambda-diff
Commits
3b6afdd7
Commit
3b6afdd7
authored
18 years ago
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
+2
-2
2 additions, 2 deletions
doc/src/sgml/ref/cluster.sgml
doc/src/sgml/ref/truncate.sgml
+32
-29
32 additions, 29 deletions
doc/src/sgml/ref/truncate.sgml
with
34 additions
and
31 deletions
doc/src/sgml/ref/cluster.sgml
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3b6afdd7
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/cluster.sgml,v 1.4
2
2007/0
4/08 02:07:35 tgl
Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/cluster.sgml,v 1.4
3
2007/0
5/11 19:40:07 neilc
Exp $
PostgreSQL documentation
-->
...
...
@@ -45,7 +45,7 @@ CLUSTER
not clustered. That is, no attempt is made to store new or
updated rows according to their index order. (If one wishes, one can
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
are preferentially kept on the same page.)
</para>
...
...
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doc/src/sgml/ref/truncate.sgml
+
32
−
29
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3b6afdd7
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/truncate.sgml,v 1.2
3
2007/0
4/07 17:12:15 tgl
Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/truncate.sgml,v 1.2
4
2007/0
5/11 19:40:08 neilc
Exp $
PostgreSQL documentation
-->
...
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@@ -31,9 +31,9 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
<command>TRUNCATE</command> quickly removes all rows from a set of
tables. It has the same effect as an unqualified
<command>DELETE</command> on each table, but since it does not actually
scan the tables it is faster
; f
urthermore it reclaims disk space
immediately, rather than requiring a subsequent
vacuum operation.
This is most useful on large tables.
scan the tables it is faster
. F
urthermore
,
it reclaims disk space
immediately, rather than requiring a subsequent
<command>VACUUM</command>
operation.
This is most useful on large tables.
</para>
</refsect1>
...
...
@@ -86,35 +86,38 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
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</>
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!
</para>
<para>
<command>TRUNCATE</> will not run any
user-defined <
literal>
ON
DELETE</literal>
triggers that might exist for the tables.
<command>TRUNCATE</> will not run any
<literal>ON DELETE</
literal>
triggers that might exist for the tables.
</para>
<warning>
<para>
<command>TRUNCATE</> is not MVCC-safe (see <xref linkend="mvcc">
for general information about MVCC). After truncation, the table
will appear empty to all concurrent transactions, even if they
are
using a snapshot taken before the truncation occurred. This
will
only be an issue for a transaction that did not
touch the tabl
e
before the truncation
start
ed — any
transaction that has done
so would hold at least <literal>ACCESS SHARE</literal> lock,
which would block
will appear empty to all concurrent transactions, even if they
are
using a snapshot taken before the truncation occurred. This
will
only be an issue for a transaction that did not
access th
e
truncated table
before the truncation
happen
ed — any
transaction that has done so would hold at least an
<literal>ACCESS SHARE</literal> lock,
which would block
<command>TRUNCATE</> until that transaction completes. So
truncation will not cause any apparent inconsistency in the table
contents for successive queries on the same table, but it could
cause visible inconsistency between the contents of the
truncated
table and other tables.
cause visible inconsistency between the contents of the
truncated
table and other tables
in the database
.
</para>
<para>
<command>TRUNCATE</> is transaction-safe, however: the truncation
will roll back if the surrounding transaction does not commit.
will be safely rolled back if the surrounding transaction does not
commit.
</para>
</warning>
</refsect1>
<refsect1>
...
...
@@ -124,13 +127,13 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ C
Truncate the tables <literal>bigtable</literal> and <literal>fattable</literal>:
<programlisting>
TRUNCATE
TABLE
bigtable, fattable;
TRUNCATE bigtable, fattable;
</programlisting>
</para>
<para>
Truncate the table <literal>othertable</literal>, and cascade to any tables
that
are
referenc
ing
<literal>othertable</literal> via foreign-key
that referenc
e
<literal>othertable</literal> via foreign-key
constraints:
<programlisting>
...
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