Improve updatability checking for views and foreign tables.

Extend the FDW API (which we already changed for 9.3) so that an FDW can
report whether specific foreign tables are insertable/updatable/deletable.
The default assumption continues to be that they're updatable if the
relevant executor callback function is supplied by the FDW, but finer
granularity is now possible.  As a test case, add an "updatable" option to
contrib/postgres_fdw.

This patch also fixes the information_schema views, which previously did
not think that foreign tables were ever updatable, and fixes
view_is_auto_updatable() so that a view on a foreign table can be
auto-updatable.

initdb forced due to changes in information_schema views and the functions
they rely on.  This is a bit unfortunate to do post-beta1, but if we don't
change this now then we'll have another API break for FDWs when we do
change it.

Dean Rasheed, somewhat editorialized on by Tom Lane

2 files changed, 64 insertions, 0 deletions

diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 912ca8663ef..6c06f1a4367 100644
--- a/doc/src/sgml/fdwhandler.sgml
+++ b/doc/src/sgml/fdwhandler.sgml
@@ -565,6 +565,33 @@ EndForeignModify (EState *estate,
      <literal>NULL</>, no action is taken during executor shutdown.
     </para>
 
+    <para>
+<programlisting>
+int
+IsForeignRelUpdatable (Relation rel);
+</programlisting>
+
+     Report which update operations the specified foreign table supports.
+     The return value should be a bitmask of rule event numbers indicating
+     which operations are supported by the foreign table, using the
+     <literal>CmdType</> enumeration; that is,
+     <literal>(1 << CMD_UPDATE) = 4</> for <command>UPDATE</>,
+     <literal>(1 << CMD_INSERT) = 8</> for <command>INSERT</>, and
+     <literal>(1 << CMD_DELETE) = 16</> for <command>DELETE</>.
+    </para>
+
+    <para>
+     If the <function>IsForeignRelUpdatable</> pointer is set to
+     <literal>NULL</>, foreign tables are assumed to be insertable, updatable,
+     or deletable if the FDW provides <function>ExecForeignInsert</>,
+     <function>ExecForeignUpdate</>, or <function>ExecForeignDelete</>
+     respectively.  This function is only needed if the FDW supports some
+     tables that are updatable and some that are not.  (Even then, it's
+     permissible to throw an error in the execution routine instead of
+     checking in this function.  However, this function is used to determine
+     updatability for display in the <literal>information_schema</> views.)
+    </para>
+
    </sect2>
 
    <sect2 id="fdw-callbacks-explain">
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml
index a1c3bebb097..35924f19f26 100644
--- a/doc/src/sgml/postgres-fdw.sgml
+++ b/doc/src/sgml/postgres-fdw.sgml
@@ -254,6 +254,43 @@
    </para>
 
   </sect3>
+
+  <sect3>
+   <title>Updatability Options</title>
+
+   <para>
+    By default all foreign tables using <filename>postgres_fdw</> are assumed
+    to be updatable.  This may be overridden using the following option:
+   </para>
+
+   <variablelist>
+
+    <varlistentry>
+     <term><literal>updatable</literal></term>
+     <listitem>
+      <para>
+       This option controls whether <filename>postgres_fdw</> allows foreign
+       tables to be modified using <command>INSERT</>, <command>UPDATE</> and
+       <command>DELETE</> commands.  It can be specified for a foreign table
+       or a foreign server.  A table-level option overrides a server-level
+       option.
+       The default is <literal>true</>.
+      </para>
+
+      <para>
+       Of course, if the remote table is not in fact updatable, an error
+       would occur anyway.  Use of this option primarily allows the error to
+       be thrown locally without querying the remote server.  Note however
+       that the <literal>information_schema</> views will report a
+       <filename>postgres_fdw</> foreign table to be updatable (or not)
+       according to the setting of this option, without any check of the
+       remote server.
+      </para>
+     </listitem>
+    </varlistentry>
+
+   </variablelist>
+  </sect3>
  </sect2>
 
  <sect2>