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Extend ALTER TABLE to allow Foreign Keys to be added without initial validation.

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FK constraints that are marked NOT VALID may later be VALIDATED, which uses an
ShareUpdateExclusiveLock on constraint table and RowShareLock on referenced
table. Significantly reduces lock strength and duration when adding FKs.
New state visible from psql.

Simon Riggs, with reviews from Marko Tiikkaja and Robert Haas
This commit is contained in:
Simon Riggs
2011-02-08 12:23:20 +00:00
parent 7202ad7b8d
commit 722bf7017b
15 changed files with 215 additions and 32 deletions
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22
doc/src/sgml/ref/alter_table.sgml
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@ -44,6 +44,8 @@ ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
ADD <replaceable class="PARAMETER">table_constraint</replaceable>
ADD <replaceable class="PARAMETER">table_constraint_using_index</replaceable>
ADD <replaceable class="PARAMETER">table_constraint</replaceable> [ NOT VALID ]
VALIDATE CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable>
DROP CONSTRAINT [ IF EXISTS ] <replaceable class="PARAMETER">constraint_name</replaceable> [ RESTRICT | CASCADE ]
DISABLE TRIGGER [ <replaceable class="PARAMETER">trigger_name</replaceable> | ALL | USER ]
ENABLE TRIGGER [ <replaceable class="PARAMETER">trigger_name</replaceable> | ALL | USER ]
@ -227,11 +229,27 @@ ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
</varlistentry>
<varlistentry>
<term><literal>ADD <replaceable class="PARAMETER">table_constraint</replaceable></literal></term>
<term><literal>ADD <replaceable class="PARAMETER">table_constraint</replaceable>
[ NOT VALID ]</literal></term>
<listitem>
<para>
This form adds a new constraint to a table using the same syntax as
<xref linkend="SQL-CREATETABLE">.
<xref linkend="SQL-CREATETABLE">. Newly added foreign key constraints can
also be defined as <literal>NOT VALID</literal> to avoid the
potentially lengthy initial check that must otherwise be performed.
Constraint checks are skipped at create table time, so
<xref linkend="SQL-CREATETABLE"> does not contain this option.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>VALIDATE CONSTRAINT</literal></term>
<listitem>
<para>
This form validates a foreign key constraint that was previously created
as <literal>NOT VALID</literal>. Constraints already marked valid do not
cause an error response.
</para>
</listitem>
</varlistentry>