On Wed, Jun 10, 2015 at 9:15 PM, Bruce Momjian <br...@momjian.us> wrote:
> I am ready to make suggested adjustments
I attach a compatibility note that is clearly needed; adding this is
an open item of mine for 9.5. This concerns foreign data wrappers and
UPSERT.
--
Peter Geoghegan
diff --git a/doc/src/sgml/release-9.5.sgml b/doc/src/sgml/release-9.5.sgml
index 5b0d109..9e857bc 100644
--- a/doc/src/sgml/release-9.5.sgml
+++ b/doc/src/sgml/release-9.5.sgml
@@ -125,6 +125,34 @@
</para>
</listitem>
+ <listitem>
+ <para>
+ Foreign data wrappers that support updating foreign tables must
+ consider the possible presence of an <literal>ON CONFLICT DO
+ NOTHING</> clause on <command>INSERT</> statements (Peter
+ Geoghegan)
+ </para>
+
+ <para>
+ When an <literal>ON CONFLICT DO NOTHING</> clause is present,
+ foreign data wrappers should either perform a
+ <productname>PostgreSQL</productname>-analogous action on the
+ foreign table, or reject the query outright.
+ </para>
+
+ <para>
+ <productname>PostgreSQL</productname> currently lacks support
+ for unique index inference against foreign tables; the
+ optimizer will always reject <command>INSERT</> statements that
+ attempt <literal>ON CONFLICT</> inference on the basis of the
+ system having no information about <quote>foreign unique
+ indexes</>. Since, in general, an inference clause is mandatory
+ for <literal>ON CONFLICT DO UPDATE</>, the <literal>DO UPDATE</>
+ variant is in effect not currently supported with foreign
+ tables.
+ </para>
+ </listitem>
+
</itemizedlist>
</sect2>
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