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

4 files changed, 55 insertions, 2 deletions

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 7a13d011d5c..38c6cf81623 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -79,6 +79,7 @@ ALTER FOREIGN TABLE ft2 DROP COLUMN cx;
 -- configure options
 ALTER SERVER testserver1 OPTIONS (
 	use_remote_estimate 'false',
+	updatable 'true',
 	fdw_startup_cost '123.456',
 	fdw_tuple_cost '0.123',
 	service 'value',
diff --git a/contrib/postgres_fdw/option.c b/contrib/postgres_fdw/option.c
index 123cb4f0104..e1d4c477339 100644
--- a/contrib/postgres_fdw/option.c
+++ b/contrib/postgres_fdw/option.c
@@ -106,9 +106,10 @@ postgres_fdw_validator(PG_FUNCTION_ARGS)
 		/*
 		 * Validate option value, when we can do so without any context.
 		 */
-		if (strcmp(def->defname, "use_remote_estimate") == 0)
+		if (strcmp(def->defname, "use_remote_estimate") == 0 ||
+			strcmp(def->defname, "updatable") == 0)
 		{
-			/* use_remote_estimate accepts only boolean values */
+			/* these accept only boolean values */
 			(void) defGetBoolean(def);
 		}
 		else if (strcmp(def->defname, "fdw_startup_cost") == 0 ||
@@ -151,6 +152,9 @@ InitPgFdwOptions(void)
 		/* cost factors */
 		{"fdw_startup_cost", ForeignServerRelationId, false},
 		{"fdw_tuple_cost", ForeignServerRelationId, false},
+		/* updatable is available on both server and table */
+		{"updatable", ForeignServerRelationId, false},
+		{"updatable", ForeignTableRelationId, false},
 		{NULL, InvalidOid, false}
 	};
 
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index cbfecc4dd42..1c93e0c5ac3 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -277,6 +277,7 @@ static TupleTableSlot *postgresExecForeignDelete(EState *estate,
 						  TupleTableSlot *planSlot);
 static void postgresEndForeignModify(EState *estate,
 						 ResultRelInfo *resultRelInfo);
+static int	postgresIsForeignRelUpdatable(Relation rel);
 static void postgresExplainForeignScan(ForeignScanState *node,
 						   ExplainState *es);
 static void postgresExplainForeignModify(ModifyTableState *mtstate,
@@ -355,6 +356,7 @@ postgres_fdw_handler(PG_FUNCTION_ARGS)
 	routine->ExecForeignUpdate = postgresExecForeignUpdate;
 	routine->ExecForeignDelete = postgresExecForeignDelete;
 	routine->EndForeignModify = postgresEndForeignModify;
+	routine->IsForeignRelUpdatable = postgresIsForeignRelUpdatable;
 
 	/* Support functions for EXPLAIN */
 	routine->ExplainForeignScan = postgresExplainForeignScan;
@@ -1597,6 +1599,51 @@ postgresEndForeignModify(EState *estate,
 }
 
 /*
+ * postgresIsForeignRelUpdatable
+ *		Determine whether a foreign table supports INSERT, UPDATE and/or
+ *		DELETE.
+ */
+static int
+postgresIsForeignRelUpdatable(Relation rel)
+{
+	bool		updatable;
+	ForeignTable *table;
+	ForeignServer *server;
+	ListCell   *lc;
+
+	/*
+	 * By default, all postgres_fdw foreign tables are assumed updatable. This
+	 * can be overridden by a per-server setting, which in turn can be
+	 * overridden by a per-table setting.
+	 */
+	updatable = true;
+
+	table = GetForeignTable(RelationGetRelid(rel));
+	server = GetForeignServer(table->serverid);
+
+	foreach(lc, server->options)
+	{
+		DefElem    *def = (DefElem *) lfirst(lc);
+
+		if (strcmp(def->defname, "updatable") == 0)
+			updatable = defGetBoolean(def);
+	}
+	foreach(lc, table->options)
+	{
+		DefElem    *def = (DefElem *) lfirst(lc);
+
+		if (strcmp(def->defname, "updatable") == 0)
+			updatable = defGetBoolean(def);
+	}
+
+	/*
+	 * Currently "updatable" means support for INSERT, UPDATE and DELETE.
+	 */
+	return updatable ?
+		(1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE) : 0;
+}
+
+/*
  * postgresExplainForeignScan
  *		Produce extra output for EXPLAIN of a ForeignScan on a foreign table
  */
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 19221680bf1..ce8bb7597ba 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -88,6 +88,7 @@ ALTER FOREIGN TABLE ft2 DROP COLUMN cx;
 -- configure options
 ALTER SERVER testserver1 OPTIONS (
 	use_remote_estimate 'false',
+	updatable 'true',
 	fdw_startup_cost '123.456',
 	fdw_tuple_cost '0.123',
 	service 'value',