diff options
| -rw-r--r-- | doc/src/sgml/ddl.sgml | 9 | ||||
| -rw-r--r-- | doc/src/sgml/ref/create_foreign_table.sgml | 30 |
2 files changed, 29 insertions, 10 deletions
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml index 296f3ff59df..166b7a352df 100644 --- a/doc/src/sgml/ddl.sgml +++ b/doc/src/sgml/ddl.sgml @@ -3791,9 +3791,12 @@ VALUES ('Albany', NULL, NULL, 'NY'); </para> <para> - Partitions can also be foreign tables, although they have some limitations - that normal tables do not; see <xref linkend="sql-createforeigntable"/> for - more information. + Partitions can also be <link linkend="ddl-foreign-data">foreign + tables</link>, although considerable care is needed because it is then + the user's responsibility that the contents of the foreign table + satisfy the partitioning rule. There are some other restrictions as + well. See <xref linkend="sql-createforeigntable"/> for more + information. </para> <sect3 id="ddl-partitioning-declarative-example"> diff --git a/doc/src/sgml/ref/create_foreign_table.sgml b/doc/src/sgml/ref/create_foreign_table.sgml index 9674670e042..b374d8645db 100644 --- a/doc/src/sgml/ref/create_foreign_table.sgml +++ b/doc/src/sgml/ref/create_foreign_table.sgml @@ -348,11 +348,33 @@ CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] constraints on foreign tables, it does assume that they are correct for purposes of query optimization. If there are rows visible in the foreign table that do not satisfy a declared constraint, queries on - the table might produce incorrect answers. It is the user's + the table might produce errors or incorrect answers. It is the user's responsibility to ensure that the constraint definition matches reality. </para> + <caution> + <para> + When a foreign table is used as a partition of a partitioned table, + there is an implicit constraint that its contents must satisfy the + partitioning rule. Again, it is the user's responsibility to ensure + that that is true, which is best done by installing a matching + constraint on the remote server. + </para> + </caution> + + <para> + Within a partitioned table containing foreign-table partitions, + an <command>UPDATE</command> that changes the partition key value can + cause a row to be moved from a local partition to a foreign-table + partition, provided the foreign data wrapper supports tuple routing. + However it is not currently possible to move a row from a + foreign-table partition to another partition. + An <command>UPDATE</command> that would require doing that will fail + due to the partitioning constraint, assuming that that is properly + enforced by the remote server. + </para> + <para> Similar considerations apply to generated columns. Stored generated columns are computed on insert or update on the local @@ -362,12 +384,6 @@ CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] generated columns that are consistent with the generation expression. Again, this might result in incorrect query results. </para> - - <para> - While rows can be moved from local partitions to a foreign-table partition - (provided the foreign data wrapper supports tuple routing), they cannot be - moved from a foreign-table partition to another partition. - </para> </refsect1> <refsect1 id="sql-createforeigntable-examples"> |