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doc: Some copy-editing around constraint validation and enforcement

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Author: Robert Treat <rob@xzilla.net>
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CACJufxFo4yTwzbSZrP%2BzQiR6_M00skoZMFaUnNJCdY6he%3DuQfA%40mail.gmail.com
This commit is contained in:
Peter Eisentraut
2025-06-25 12:44:03 +02:00
parent 60dda7bbc4
commit 62a47aea1d
1 changed files with 8 additions and 8 deletions
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16
doc/src/sgml/ref/alter_table.sgml
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@ -460,8 +460,8 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
<para> <para>
This form adds a new constraint to a table using the same constraint This form adds a new constraint to a table using the same constraint
syntax as <link linkend="sql-createtable"><command>CREATE TABLE</command></link>, plus the option <literal>NOT syntax as <link linkend="sql-createtable"><command>CREATE TABLE</command></link>, plus the option <literal>NOT
VALID</literal>, which is currently only allowed for foreign key, VALID</literal>, which is currently only allowed for foreign-key,
<literal>CHECK</literal> constraints and not-null constraints. <literal>CHECK</literal>, and not-null constraints.
</para> </para>
<para> <para>
@ -469,7 +469,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
existing rows in the table satisfy the new constraint. But if existing rows in the table satisfy the new constraint. But if
the <literal>NOT VALID</literal> option is used, this the <literal>NOT VALID</literal> option is used, this
potentially-lengthy scan is skipped. The constraint will still be potentially-lengthy scan is skipped. The constraint will still be
enforced against subsequent inserts or updates (that is, they'll fail applied against subsequent inserts or updates (that is, they'll fail
unless there is a matching row in the referenced table, in the case unless there is a matching row in the referenced table, in the case
of foreign keys, or they'll fail unless the new row matches the of foreign keys, or they'll fail unless the new row matches the
specified check condition). But the specified check condition). But the
@ -591,7 +591,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
This form validates a foreign key, check, or not-null constraint that was This form validates a foreign key, check, or not-null constraint that was
previously created as <literal>NOT VALID</literal>, by scanning the previously created as <literal>NOT VALID</literal>, by scanning the
table to ensure there are no rows for which the constraint is not table to ensure there are no rows for which the constraint is not
satisfied. If the constraint is not enforced, an error is thrown. satisfied. If the constraint was set to <literal>NOT ENFORCED</literal>, an error is thrown.
Nothing happens if the constraint is already marked valid. Nothing happens if the constraint is already marked valid.
(See <xref linkend="sql-altertable-notes"/> below for an explanation (See <xref linkend="sql-altertable-notes"/> below for an explanation
of the usefulness of this command.) of the usefulness of this command.)
@ -1466,11 +1466,11 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</para> </para>
<para> <para>
Adding an enforced <literal>CHECK</literal> or <literal>NOT NULL</literal> Adding a <literal>CHECK</literal> or <literal>NOT NULL</literal>
constraint requires scanning the table to verify that existing rows meet the constraint requires scanning the table to verify that existing rows meet the
constraint, but does not require a table rewrite. If a <literal>CHECK</literal> constraint, but does not require a table rewrite. If a <literal>CHECK</literal>
constraint is added as <literal>NOT ENFORCED</literal>, the validation will constraint is added as <literal>NOT ENFORCED</literal>, no verification will
not be performed. be performed.
</para> </para>
<para> <para>
@ -1485,7 +1485,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</para> </para>
<para> <para>
Scanning a large table to verify a new foreign key or check constraint Scanning a large table to verify new foreign-key, check, or not-null constraints
can take a long time, and other updates to the table are locked out can take a long time, and other updates to the table are locked out
until the <command>ALTER TABLE ADD CONSTRAINT</command> command is until the <command>ALTER TABLE ADD CONSTRAINT</command> command is
committed. The main purpose of the <literal>NOT VALID</literal> committed. The main purpose of the <literal>NOT VALID</literal>