postgres.git / summary / log / commit / refs

commit    b70db6c83073b562a92aaba917aa787c46ea1b39
Author:   David Rowley <drowley@postgresql.org>
Date:     Mon Sep 05 06:44:44 2022 +0000

    Doc: clarify partitioned table limitations
    
    Improve documentation regarding the limitations of unique and primary key
    constraints on partitioned tables.  The existing documentation didn't make
    it clear that the constraint columns had to be present in the partition
    key as bare columns.  The reader could be led to believe that it was ok to
    include the constraint columns as part of a function call's parameters or
    as part of an expression.  Additionally, the documentation didn't mention
    anything about the fact that we disallow unique and primary key
    constraints if the partition keys contain *any* function calls or
    expressions, regardless of if the constraint columns appear as columns
    elsewhere in the partition key.
    
    The confusion here was highlighted by a report on the general mailing list
    by James Vanns.
    
    Discussion: https://postgr.es/m/CAH7vdhNF0EdYZz3GLpgE3RSJLwWLhEk7A_fiKS9dPBT3Dz_3eA@mail.gmail.com
    Discussion: https://postgr.es/m/CAApHDvoU-u9iTqKjteYRFfi+UNEk7dbSAcyxEQD==vZt9B1KnA@mail.gmail.com
    Reviewed-by: Erik Rijkers
    Backpatch-through: 11


 doc/src/sgml/ddl.sgml | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 4ba45891cb6..1f7a352a66d 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -4055,12 +4055,13 @@ ALTER INDEX measurement_city_id_logdate_key
     <itemizedlist>
      <listitem>
       <para>
-       Unique constraints (and hence primary keys) on partitioned tables must
-       include all the partition key columns.  This limitation exists because
-       the individual indexes making up the constraint can only directly
-       enforce uniqueness within their own partitions; therefore, the
-       partition structure itself must guarantee that there are not
-       duplicates in different partitions.
+       To create a unique or primary key constraint on a partitioned table,
+       the partition keys must not include any expressions or function calls
+       and the constraint's columns must include all of the partition key
+       columns.  This limitation exists because the individual indexes making
+       up the constraint can only directly enforce uniqueness within their own
+       partitions; therefore, the partition structure itself must guarantee
+       that there are not duplicates in different partitions.
       </para>
      </listitem>
 


[parent: 0cc46c825135]