Create the catalog infrastructure for foreign-data-wrapper handlers.

Add a fdwhandler column to pg_foreign_data_wrapper, plus HANDLER options
in the CREATE FOREIGN DATA WRAPPER and ALTER FOREIGN DATA WRAPPER commands,
plus pg_dump support for same.  Also invent a new pseudotype fdw_handler
with properties similar to language_handler.

This is split out of the "FDW API" patch for ease of review; it's all stuff
we will certainly need, regardless of any other details of the FDW API.
FDW handler functions will not actually get called yet.

In passing, fix some omissions and infelicities in foreigncmds.c.

Shigeru Hanada, Jan Urbanski, Heikki Linnakangas

6 files changed, 235 insertions, 58 deletions

diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index a2b5358e16f..acd40c1f4e9 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -165,7 +165,7 @@ transformGenericOptions(Oid catalogId,
 
 	result = optionListToArray(resultOptions);
 
-	if (fdwvalidator)
+	if (OidIsValid(fdwvalidator) && DatumGetPointer(result) != NULL)
 		OidFunctionCall2(fdwvalidator, result, ObjectIdGetDatum(catalogId));
 
 	return result;
@@ -246,8 +246,9 @@ AlterForeignDataWrapperOwner(const char *name, Oid newOwnerId)
 								newOwnerId);
 	}
 
-	heap_close(rel, NoLock);
 	heap_freetuple(tup);
+
+	heap_close(rel, RowExclusiveLock);
 }
 
 
@@ -308,25 +309,98 @@ AlterForeignServerOwner(const char *name, Oid newOwnerId)
 								newOwnerId);
 	}
 
-	heap_close(rel, NoLock);
 	heap_freetuple(tup);
+
+	heap_close(rel, RowExclusiveLock);
 }
 
 
 /*
+ * Convert a handler function name passed from the parser to an Oid.
+ */
+static Oid
+lookup_fdw_handler_func(DefElem *handler)
+{
+	Oid			handlerOid;
+
+	if (handler == NULL || handler->arg == NULL)
+		return InvalidOid;
+
+	/* handlers have no arguments */
+	handlerOid = LookupFuncName((List *) handler->arg, 0, NULL, false);
+
+	/* check that handler has correct return type */
+	if (get_func_rettype(handlerOid) != FDW_HANDLEROID)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("function %s must return type \"fdw_handler\"",
+						NameListToString((List *) handler->arg))));
+
+	return handlerOid;
+}
+
+/*
  * Convert a validator function name passed from the parser to an Oid.
  */
 static Oid
-lookup_fdw_validator_func(List *validator)
+lookup_fdw_validator_func(DefElem *validator)
 {
 	Oid			funcargtypes[2];
 
+	if (validator == NULL || validator->arg == NULL)
+		return InvalidOid;
+
+	/* validators take text[], oid */
 	funcargtypes[0] = TEXTARRAYOID;
 	funcargtypes[1] = OIDOID;
-	return LookupFuncName(validator, 2, funcargtypes, false);
-	/* return value is ignored, so we don't check the type */
+
+	return LookupFuncName((List *) validator->arg, 2, funcargtypes, false);
+	/* validator's return value is ignored, so we don't check the type */
 }
 
+/*
+ * Process function options of CREATE/ALTER FDW
+ */
+static void
+parse_func_options(List *func_options,
+				   bool *handler_given, Oid *fdwhandler,
+				   bool *validator_given, Oid *fdwvalidator)
+{
+	ListCell   *cell;
+
+	*handler_given = false;
+	*validator_given = false;
+	/* return InvalidOid if not given */
+	*fdwhandler = InvalidOid;
+	*fdwvalidator = InvalidOid;
+
+	foreach(cell, func_options)
+	{
+		DefElem    *def = (DefElem *) lfirst(cell);
+
+		if (strcmp(def->defname, "handler") == 0)
+		{
+			if (*handler_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			*handler_given = true;
+			*fdwhandler = lookup_fdw_handler_func(def);
+		}
+		else if (strcmp(def->defname, "validator") == 0)
+		{
+			if (*validator_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			*validator_given = true;
+			*fdwvalidator = lookup_fdw_validator_func(def);
+		}
+		else
+			elog(ERROR, "option \"%s\" not recognized",
+				 def->defname);
+	}
+}
 
 /*
  * Create a foreign-data wrapper
@@ -339,6 +413,9 @@ CreateForeignDataWrapper(CreateFdwStmt *stmt)
 	bool		nulls[Natts_pg_foreign_data_wrapper];
 	HeapTuple	tuple;
 	Oid			fdwId;
+	bool		handler_given;
+	bool		validator_given;
+	Oid			fdwhandler;
 	Oid			fdwvalidator;
 	Datum		fdwoptions;
 	Oid			ownerId;
@@ -377,12 +454,13 @@ CreateForeignDataWrapper(CreateFdwStmt *stmt)
 		DirectFunctionCall1(namein, CStringGetDatum(stmt->fdwname));
 	values[Anum_pg_foreign_data_wrapper_fdwowner - 1] = ObjectIdGetDatum(ownerId);
 
-	if (stmt->validator)
-		fdwvalidator = lookup_fdw_validator_func(stmt->validator);
-	else
-		fdwvalidator = InvalidOid;
+	/* Lookup handler and validator functions, if given */
+	parse_func_options(stmt->func_options,
+					   &handler_given, &fdwhandler,
+					   &validator_given, &fdwvalidator);
 
-	values[Anum_pg_foreign_data_wrapper_fdwvalidator - 1] = fdwvalidator;
+	values[Anum_pg_foreign_data_wrapper_fdwhandler - 1] = ObjectIdGetDatum(fdwhandler);
+	values[Anum_pg_foreign_data_wrapper_fdwvalidator - 1] = ObjectIdGetDatum(fdwvalidator);
 
 	nulls[Anum_pg_foreign_data_wrapper_fdwacl - 1] = true;
 
@@ -408,7 +486,15 @@ CreateForeignDataWrapper(CreateFdwStmt *stmt)
 	myself.objectId = fdwId;
 	myself.objectSubId = 0;
 
-	if (fdwvalidator)
+	if (OidIsValid(fdwhandler))
+	{
+		referenced.classId = ProcedureRelationId;
+		referenced.objectId = fdwhandler;
+		referenced.objectSubId = 0;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	if (OidIsValid(fdwvalidator))
 	{
 		referenced.classId = ProcedureRelationId;
 		referenced.objectId = fdwvalidator;
@@ -425,7 +511,7 @@ CreateForeignDataWrapper(CreateFdwStmt *stmt)
 	InvokeObjectAccessHook(OAT_POST_CREATE,
 						   ForeignDataWrapperRelationId, fdwId, 0);
 
-	heap_close(rel, NoLock);
+	heap_close(rel, RowExclusiveLock);
 }
 
 
@@ -437,12 +523,16 @@ AlterForeignDataWrapper(AlterFdwStmt *stmt)
 {
 	Relation	rel;
 	HeapTuple	tp;
+	Form_pg_foreign_data_wrapper fdwForm;
 	Datum		repl_val[Natts_pg_foreign_data_wrapper];
 	bool		repl_null[Natts_pg_foreign_data_wrapper];
 	bool		repl_repl[Natts_pg_foreign_data_wrapper];
 	Oid			fdwId;
 	bool		isnull;
 	Datum		datum;
+	bool		handler_given;
+	bool		validator_given;
+	Oid			fdwhandler;
 	Oid			fdwvalidator;
 
 	/* Must be super user */
@@ -461,15 +551,32 @@ AlterForeignDataWrapper(AlterFdwStmt *stmt)
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
 		errmsg("foreign-data wrapper \"%s\" does not exist", stmt->fdwname)));
 
+	fdwForm = (Form_pg_foreign_data_wrapper) GETSTRUCT(tp);
 	fdwId = HeapTupleGetOid(tp);
 
 	memset(repl_val, 0, sizeof(repl_val));
 	memset(repl_null, false, sizeof(repl_null));
 	memset(repl_repl, false, sizeof(repl_repl));
 
-	if (stmt->change_validator)
+	parse_func_options(stmt->func_options,
+					   &handler_given, &fdwhandler,
+					   &validator_given, &fdwvalidator);
+
+	if (handler_given)
+	{
+		repl_val[Anum_pg_foreign_data_wrapper_fdwhandler - 1] = ObjectIdGetDatum(fdwhandler);
+		repl_repl[Anum_pg_foreign_data_wrapper_fdwhandler - 1] = true;
+
+		/*
+		 * It could be that the behavior of accessing foreign table changes
+		 * with the new handler.  Warn about this.
+		 */
+		ereport(WARNING,
+				(errmsg("changing the foreign-data wrapper handler can change behavior of existing foreign tables")));
+	}
+
+	if (validator_given)
 	{
-		fdwvalidator = stmt->validator ? lookup_fdw_validator_func(stmt->validator) : InvalidOid;
 		repl_val[Anum_pg_foreign_data_wrapper_fdwvalidator - 1] = ObjectIdGetDatum(fdwvalidator);
 		repl_repl[Anum_pg_foreign_data_wrapper_fdwvalidator - 1] = true;
 
@@ -477,26 +584,21 @@ AlterForeignDataWrapper(AlterFdwStmt *stmt)
 		 * It could be that the options for the FDW, SERVER and USER MAPPING
 		 * are no longer valid with the new validator.	Warn about this.
 		 */
-		if (stmt->validator)
+		if (OidIsValid(fdwvalidator))
 			ereport(WARNING,
-			 (errmsg("changing the foreign-data wrapper validator can cause "
-					 "the options for dependent objects to become invalid")));
+					(errmsg("changing the foreign-data wrapper validator can cause "
+							"the options for dependent objects to become invalid")));
 	}
 	else
 	{
 		/*
 		 * Validator is not changed, but we need it for validating options.
 		 */
-		datum = SysCacheGetAttr(FOREIGNDATAWRAPPEROID,
-								tp,
-								Anum_pg_foreign_data_wrapper_fdwvalidator,
-								&isnull);
-		Assert(!isnull);
-		fdwvalidator = DatumGetObjectId(datum);
+		fdwvalidator = fdwForm->fdwvalidator;
 	}
 
 	/*
-	 * Options specified, validate and update.
+	 * If options specified, validate and update.
 	 */
 	if (stmt->options)
 	{
@@ -532,8 +634,46 @@ AlterForeignDataWrapper(AlterFdwStmt *stmt)
 	simple_heap_update(rel, &tp->t_self, tp);
 	CatalogUpdateIndexes(rel, tp);
 
-	heap_close(rel, RowExclusiveLock);
 	heap_freetuple(tp);
+
+	/* Update function dependencies if we changed them */
+	if (handler_given || validator_given)
+	{
+		ObjectAddress myself;
+		ObjectAddress referenced;
+
+		/*
+		 * Flush all existing dependency records of this FDW on functions;
+		 * we assume there can be none other than the ones we are fixing.
+		 */
+		deleteDependencyRecordsForClass(ForeignDataWrapperRelationId,
+										fdwId,
+										ProcedureRelationId,
+										DEPENDENCY_NORMAL);
+
+		/* And build new ones. */
+		myself.classId = ForeignDataWrapperRelationId;
+		myself.objectId = fdwId;
+		myself.objectSubId = 0;
+
+		if (OidIsValid(fdwhandler))
+		{
+			referenced.classId = ProcedureRelationId;
+			referenced.objectId = fdwhandler;
+			referenced.objectSubId = 0;
+			recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+		}
+
+		if (OidIsValid(fdwvalidator))
+		{
+			referenced.classId = ProcedureRelationId;
+			referenced.objectId = fdwvalidator;
+			referenced.objectSubId = 0;
+			recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+		}
+	}
+
+	heap_close(rel, RowExclusiveLock);
 }
 
 
@@ -712,7 +852,7 @@ CreateForeignServer(CreateForeignServerStmt *stmt)
 	/* Post creation hook for new foreign server */
 	InvokeObjectAccessHook(OAT_POST_CREATE, ForeignServerRelationId, srvId, 0);
 
-	heap_close(rel, NoLock);
+	heap_close(rel, RowExclusiveLock);
 }
 
 
@@ -804,8 +944,9 @@ AlterForeignServer(AlterForeignServerStmt *stmt)
 	simple_heap_update(rel, &tp->t_self, tp);
 	CatalogUpdateIndexes(rel, tp);
 
-	heap_close(rel, RowExclusiveLock);
 	heap_freetuple(tp);
+
+	heap_close(rel, RowExclusiveLock);
 }
 
 
@@ -991,7 +1132,7 @@ CreateUserMapping(CreateUserMappingStmt *stmt)
 	/* Post creation hook for new user mapping */
 	InvokeObjectAccessHook(OAT_POST_CREATE, UserMappingRelationId, umId, 0);
 
-	heap_close(rel, NoLock);
+	heap_close(rel, RowExclusiveLock);
 }
 
 
@@ -1076,8 +1217,9 @@ AlterUserMapping(AlterUserMappingStmt *stmt)
 	simple_heap_update(rel, &tp->t_self, tp);
 	CatalogUpdateIndexes(rel, tp);
 
-	heap_close(rel, RowExclusiveLock);
 	heap_freetuple(tp);
+
+	heap_close(rel, RowExclusiveLock);
 }
 
 
@@ -1184,7 +1326,6 @@ CreateForeignTable(CreateForeignTableStmt *stmt, Oid relid)
 	Datum		values[Natts_pg_foreign_table];
 	bool		nulls[Natts_pg_foreign_table];
 	HeapTuple	tuple;
-	Oid			ftId;
 	AclResult	aclresult;
 	ObjectAddress myself;
 	ObjectAddress referenced;
@@ -1237,9 +1378,7 @@ CreateForeignTable(CreateForeignTableStmt *stmt, Oid relid)
 
 	tuple = heap_form_tuple(ftrel->rd_att, values, nulls);
 
-	/* pg_foreign_table don't have OID */
-	ftId = simple_heap_insert(ftrel, tuple);
-
+	simple_heap_insert(ftrel, tuple);
 	CatalogUpdateIndexes(ftrel, tuple);
 
 	heap_freetuple(tuple);
@@ -1254,5 +1393,5 @@ CreateForeignTable(CreateForeignTableStmt *stmt, Oid relid)
 	referenced.objectSubId = 0;
 	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
 
-	heap_close(ftrel, NoLock);
+	heap_close(ftrel, RowExclusiveLock);
 }
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index 9a0f847f93c..6e391025ffa 100644
--- a/src/backend/foreign/foreign.c
+++ b/src/backend/foreign/foreign.c
@@ -58,6 +58,7 @@ GetForeignDataWrapper(Oid fdwid)
 	fdw->fdwid = fdwid;
 	fdw->owner = fdwform->fdwowner;
 	fdw->fdwname = pstrdup(NameStr(fdwform->fdwname));
+	fdw->fdwhandler = fdwform->fdwhandler;
 	fdw->fdwvalidator = fdwform->fdwvalidator;
 
 	/* Extract the options */
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 57d58020810..9a8a97c4bec 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3282,7 +3282,7 @@ _copyCreateFdwStmt(CreateFdwStmt *from)
 	CreateFdwStmt *newnode = makeNode(CreateFdwStmt);
 
 	COPY_STRING_FIELD(fdwname);
-	COPY_NODE_FIELD(validator);
+	COPY_NODE_FIELD(func_options);
 	COPY_NODE_FIELD(options);
 
 	return newnode;
@@ -3294,8 +3294,7 @@ _copyAlterFdwStmt(AlterFdwStmt *from)
 	AlterFdwStmt *newnode = makeNode(AlterFdwStmt);
 
 	COPY_STRING_FIELD(fdwname);
-	COPY_NODE_FIELD(validator);
-	COPY_SCALAR_FIELD(change_validator);
+	COPY_NODE_FIELD(func_options);
 	COPY_NODE_FIELD(options);
 
 	return newnode;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index f57cf99ba2c..dd332f19f00 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1679,7 +1679,7 @@ static bool
 _equalCreateFdwStmt(CreateFdwStmt *a, CreateFdwStmt *b)
 {
 	COMPARE_STRING_FIELD(fdwname);
-	COMPARE_NODE_FIELD(validator);
+	COMPARE_NODE_FIELD(func_options);
 	COMPARE_NODE_FIELD(options);
 
 	return true;
@@ -1689,8 +1689,7 @@ static bool
 _equalAlterFdwStmt(AlterFdwStmt *a, AlterFdwStmt *b)
 {
 	COMPARE_STRING_FIELD(fdwname);
-	COMPARE_NODE_FIELD(validator);
-	COMPARE_SCALAR_FIELD(change_validator);
+	COMPARE_NODE_FIELD(func_options);
 	COMPARE_NODE_FIELD(options);
 
 	return true;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 077a10532eb..c6811a11bd1 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -309,6 +309,9 @@ static RangeVar *makeRangeVarFromAnyName(List *names, int position, core_yyscan_
 				create_generic_options alter_generic_options
 				relation_expr_list dostmt_opt_list
 
+%type <list>	opt_fdw_options fdw_options
+%type <defelt>	fdw_option
+
 %type <range>	OptTempTableName
 %type <into>	into_clause create_as_target
 
@@ -3505,20 +3508,37 @@ AlterExtensionContentsStmt:
 /*****************************************************************************
  *
  * 		QUERY:
- *             CREATE FOREIGN DATA WRAPPER name [ VALIDATOR name ]
+ *             CREATE FOREIGN DATA WRAPPER name options
  *
  *****************************************************************************/
 
-CreateFdwStmt: CREATE FOREIGN DATA_P WRAPPER name opt_validator create_generic_options
+CreateFdwStmt: CREATE FOREIGN DATA_P WRAPPER name opt_fdw_options create_generic_options
 				{
 					CreateFdwStmt *n = makeNode(CreateFdwStmt);
 					n->fdwname = $5;
-					n->validator = $6;
+					n->func_options = $6;
 					n->options = $7;
 					$$ = (Node *) n;
 				}
 		;
 
+fdw_option:
+			HANDLER handler_name				{ $$ = makeDefElem("handler", (Node *)$2); }
+			| NO HANDLER						{ $$ = makeDefElem("handler", NULL); }
+			| VALIDATOR handler_name			{ $$ = makeDefElem("validator", (Node *)$2); }
+			| NO VALIDATOR						{ $$ = makeDefElem("validator", NULL); }
+		;
+
+fdw_options:
+			fdw_option							{ $$ = list_make1($1); }
+			| fdw_options fdw_option			{ $$ = lappend($1, $2); }
+		;
+
+opt_fdw_options:
+			fdw_options							{ $$ = $1; }
+			| /*EMPTY*/							{ $$ = NIL; }
+		;
+
 /*****************************************************************************
  *
  * 		QUERY :
@@ -3547,32 +3567,24 @@ DropFdwStmt: DROP FOREIGN DATA_P WRAPPER name opt_drop_behavior
 /*****************************************************************************
  *
  * 		QUERY :
- *				ALTER FOREIGN DATA WRAPPER name
+ *				ALTER FOREIGN DATA WRAPPER name options
  *
  ****************************************************************************/
 
-AlterFdwStmt: ALTER FOREIGN DATA_P WRAPPER name validator_clause alter_generic_options
+AlterFdwStmt: ALTER FOREIGN DATA_P WRAPPER name opt_fdw_options alter_generic_options
 				{
 					AlterFdwStmt *n = makeNode(AlterFdwStmt);
 					n->fdwname = $5;
-					n->validator = $6;
-					n->change_validator = true;
+					n->func_options = $6;
 					n->options = $7;
 					$$ = (Node *) n;
 				}
-			| ALTER FOREIGN DATA_P WRAPPER name validator_clause
+			| ALTER FOREIGN DATA_P WRAPPER name fdw_options
 				{
 					AlterFdwStmt *n = makeNode(AlterFdwStmt);
 					n->fdwname = $5;
-					n->validator = $6;
-					n->change_validator = true;
-					$$ = (Node *) n;
-				}
-			| ALTER FOREIGN DATA_P WRAPPER name alter_generic_options
-				{
-					AlterFdwStmt *n = makeNode(AlterFdwStmt);
-					n->fdwname = $5;
-					n->options = $6;
+					n->func_options = $6;
+					n->options = NIL;
 					$$ = (Node *) n;
 				}
 		;
diff --git a/src/backend/utils/adt/pseudotypes.c b/src/backend/utils/adt/pseudotypes.c
index 2be0696f609..d9329f83428 100644
--- a/src/backend/utils/adt/pseudotypes.c
+++ b/src/backend/utils/adt/pseudotypes.c
@@ -268,6 +268,33 @@ language_handler_out(PG_FUNCTION_ARGS)
 
 
 /*
+ * fdw_handler_in		- input routine for pseudo-type FDW_HANDLER.
+ */
+Datum
+fdw_handler_in(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("cannot accept a value of type fdw_handler")));
+
+	PG_RETURN_VOID();			/* keep compiler quiet */
+}
+
+/*
+ * fdw_handler_out		- output routine for pseudo-type FDW_HANDLER.
+ */
+Datum
+fdw_handler_out(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			 errmsg("cannot display a value of type fdw_handler")));
+
+	PG_RETURN_VOID();			/* keep compiler quiet */
+}
+
+
+/*
  * internal_in		- input routine for pseudo-type INTERNAL.
  */
 Datum