diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml index d7158c1b03..9d6ec2c738 100644 --- a/doc/src/sgml/ddl.sgml +++ b/doc/src/sgml/ddl.sgml @@ -3952,14 +3952,14 @@ ALTER TABLE measurement ATTACH PARTITION measurement_y2008m02 Before running the ATTACH PARTITION command, it is recommended to create a CHECK constraint on the table to - be attached describing the desired partition constraint. That way, + be attached matching the desired partition constraint. That way, the system will be able to skip the scan to validate the implicit - partition constraint. Without such a constraint, the table will be - scanned to validate the partition constraint while holding an - ACCESS EXCLUSIVE lock on that partition + partition constraint. Without the CHECK constraint, + the table will be scanned to validate the partition constraint while + holding an ACCESS EXCLUSIVE lock on that partition and a SHARE UPDATE EXCLUSIVE lock on the parent table. - One may then drop the constraint after ATTACH PARTITION - is finished, because it is no longer necessary. + It may be desired to drop the redundant CHECK constraint + after ATTACH PARTITION is finished. diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml index 62542cd8a1..ea11e65263 100644 --- a/doc/src/sgml/ref/alter_table.sgml +++ b/doc/src/sgml/ref/alter_table.sgml @@ -841,7 +841,7 @@ WITH ( MODULUS numeric_literal, REM or as a default partition by using DEFAULT. For each index in the target table, a corresponding one will be created in the attached table; or, if an equivalent - index already exists, will be attached to the target table's index, + index already exists, it will be attached to the target table's index, as if ALTER INDEX ATTACH PARTITION had been executed. Note that if the existing table is a foreign table, it is currently not allowed to attach the table as a partition of the target table if there @@ -864,23 +864,24 @@ WITH ( MODULUS numeric_literal, REM already exist. If any of the CHECK constraints of the table being attached is marked NO INHERIT, the command will fail; - such a constraint must be recreated without the NO INHERIT - clause. + such constraints must be recreated without the + NO INHERIT clause. If the new partition is a regular table, a full table scan is performed - to check that no existing row in the table violates the partition - constraint. It is possible to avoid this scan by adding a valid - CHECK constraint to the table that would allow only - the rows satisfying the desired partition constraint before running this - command. It will be determined using such a constraint that the table - need not be scanned to validate the partition constraint. This does not - work, however, if any of the partition keys is an expression and the - partition does not accept NULL values. If attaching - a list partition that will not accept NULL values, - also add NOT NULL constraint to the partition key - column, unless it's an expression. + to check that existing rows in the table do not violate the partition + constraint. It is possible to avoid this scan by adding a valid + CHECK constraint to the table that allows only + rows satisfying the desired partition constraint before running this + command. The CHECK constraint will be used to + determine that the table need not be scanned to validate the partition + constraint. This does not work, however, if any of the partition keys + is an expression and the partition does not accept + NULL values. If attaching a list partition that will + not accept NULL values, also add + NOT NULL constraint to the partition key column, + unless it's an expression.