From 230c594950886bf50bf4c69295aa0cb67c16b8a6 Mon Sep 17 00:00:00 2001
From: Matthias van de Meent <boekewurm@gmail.com>
Date: Thu, 15 Apr 2021 20:43:00 +0200
Subject: [PATCH v2] ATTACH PARTITION locking documentation for DEFAULT
 partitions.

---
 doc/src/sgml/ddl.sgml             | 18 ++++++++++++++++--
 doc/src/sgml/ref/alter_table.sgml |  8 ++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 30e4170963..8f0b38847a 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -3934,6 +3934,9 @@ ALTER TABLE measurement_y2008m02 ADD CONSTRAINT y2008m02
 \copy measurement_y2008m02 from 'measurement_y2008m02'
 -- possibly some other data preparation work
 
+ALTER TABLE measurement_default ADD CONSTRAINT excl_y2008m02
+   CHECK ( (logdate &gt;= DATE '2008-02-01' AND logdate &lt; DATE '2008-03-01') IS FALSE );
+
 ALTER TABLE measurement ATTACH PARTITION measurement_y2008m02
     FOR VALUES FROM ('2008-02-01') TO ('2008-03-01' );
 </programlisting>
@@ -3947,12 +3950,23 @@ ALTER TABLE measurement ATTACH PARTITION measurement_y2008m02
      which is otherwise needed to validate the implicit
      partition constraint. Without the <literal>CHECK</literal> constraint,
      the table will be scanned to validate the partition constraint while
-     holding both an <literal>ACCESS EXCLUSIVE</literal> lock on that partition
-     and a <literal>SHARE UPDATE EXCLUSIVE</literal> lock on the parent table.
+     holding an <literal>ACCESS EXCLUSIVE</literal> lock on that partition
+     and the tables in its downward partition hierarchy (if any), and a 
+     <literal>SHARE UPDATE EXCLUSIVE</literal> lock on the parent table.
      It is recommended to drop the now-redundant <literal>CHECK</literal>
      constraint after <command>ATTACH PARTITION</command> is finished.
     </para>
 
+    <para>
+     Similarly, if you have a default partition on the parent table, it is
+     recommended to create a <literal>CHECK</literal> constraint that excludes
+     the to be attached partition constraint. If the default partition does
+     not exclude the to be attached partition constraint, the partition
+     hierarchy of the default partition will recursively be checked against
+     the updated partition bounds whilst holding an 
+     <literal>ACCESS EXCLUSIVE</literal> lock.
+    </para>
+
     <para>
      As explained above, it is possible to create indexes on partitioned tables
      so that they are applied automatically to the entire hierarchy.
diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 07e37a6dc8..2801d87827 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -947,8 +947,12 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
      <para>
       Attaching a partition acquires a
       <literal>SHARE UPDATE EXCLUSIVE</literal> lock on the parent table,
-      in addition to <literal>ACCESS EXCLUSIVE</literal> locks on the table
-      to be attached and on the default partition (if any).
+      in addition to <literal>ACCESS EXCLUSIVE</literal> locks on the full
+      partition hierarchy of the to be attached table and on the default
+      partition (if any). If the constraints of the default partition do not
+      already imply the new partition bounds, its descendants will
+      recursively be locked with an <literal>ACCESS EXCLUSIVE</literal> lock
+      and validated against the updated constraints.
      </para>
     </listitem>
    </varlistentry>
-- 
2.20.1