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Fix docs on lock level for ALTER TABLE VALIDATE

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ALTER TABLE .. VALIDATE CONSTRAINT previously
gave incorrect details about lock levels and
therefore incomplete reasons to use the option.

Initial bug report and fix from Marko Tiikkaja
Reworded by me to include comments by Kevin Grittner
This commit is contained in:
Simon Riggs 2013-06-18 12:09:39 +01:00
parent c3c86ae2af
commit 073d7cb513
1 changed files with 7 additions and 3 deletions
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10
doc/src/sgml/ref/alter_table.sgml
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@ -324,9 +324,13 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
as <literal>NOT VALID</literal>, by scanning the table to ensure there
are no rows for which the constraint is not satisfied.
Nothing happens if the constraint is already marked valid.
The value of separating validation from initial creation of the
constraint is that validation requires a lesser lock on the table
than constraint creation does.
</para>
<para>
Validation can be a long process on larger tables and currently requires
an <literal>ACCESS EXCLUSIVE</literal> lock. The value of separating
validation from initial creation is that you can defer validation to less
busy times, or can be used to give additional time to correct pre-existing
errors while preventing new errors.
</para>
</listitem>
</varlistentry>