src/backend/catalog/pg_proc_callback.c

/*-------------------------------------------------------------------------
 *
 * pg_proc_callback.c
 *	  
 *   Auxillary extension to pg_proc to enable defining additional callback
 *   functions.  Currently the list of allowable callback functions is small
 *   and consists of:
 *     - DESCRIBE() - to support more complex pseudotype resolution
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "catalog/catquery.h"
#include "catalog/indexing.h"
#include "catalog/pg_proc_callback.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/tqual.h"

/* ---------------------
 * deleteProcCallbacks() - Remove callbacks from pg_proc_callback
 *
 * Parameters:
 *    profnoid - remove all callbacks for this function oid
 *
 * Notes:
 *    This function does not maintain dependencies in pg_depend, that behavior
 *    is currently controlled in pg_proc.c
 * ---------------------
 */
void 
deleteProcCallbacks(Oid profnoid)
{
	int numDel;

	Insist(OidIsValid(profnoid));

	/* 
	 * Boiler template code to loop through the index and remove all matching
	 * rows.
	 */

	numDel = 
			caql_getcount(
					NULL,
					cql("DELETE FROM pg_proc_callback "
						" WHERE profnoid = :1 ",
						ObjectIdGetDatum(profnoid)));
}


/* ---------------------
 * addProcCallback() - Add a new callback to pg_proc_callback
 *
 * Parameters:
 *    profnoid    - oid of the function that has a callback
 *    procallback - oid of the callback function
 *    promethod   - role the callback function plays
 *
 * Notes:
 *    This function does not maintain dependencies in pg_depend, that behavior
 *    is currently controlled in pg_proc.c
 * ---------------------
 */
void 
addProcCallback(Oid profnoid, Oid procallback, char promethod)
{
	bool		nulls[Natts_pg_proc_callback];
	Datum		values[Natts_pg_proc_callback];
	HeapTuple   tup;
	cqContext  *pcqCtx;
	
	Insist(OidIsValid(profnoid));
	Insist(OidIsValid(procallback));

	/* open pg_proc_callback */
	pcqCtx = caql_beginscan(
			NULL,
			cql("INSERT INTO pg_proc_callback ",
				NULL));

	/* Build the tuple and insert it */
	nulls[Anum_pg_proc_callback_profnoid - 1]	  = false;
	nulls[Anum_pg_proc_callback_procallback - 1]  = false;
	nulls[Anum_pg_proc_callback_promethod - 1]	  = false;
	values[Anum_pg_proc_callback_profnoid - 1]	  = ObjectIdGetDatum(profnoid);
	values[Anum_pg_proc_callback_procallback - 1] = ObjectIdGetDatum(procallback);
	values[Anum_pg_proc_callback_promethod - 1]	  = CharGetDatum(promethod);

	tup = caql_form_tuple(pcqCtx, values, nulls);
	
	/* Insert tuple into the relation */
	caql_insert(pcqCtx, tup);  /* implicit update of index as well */

	caql_endscan(pcqCtx);
}


/* ---------------------
 * lookupProcCallback() - Find a specified callback for a specified function
 *
 * Parameters:
 *    profnoid    - oid of the function that has a callback
 *    promethod   - which callback to find
 * ---------------------
 */
Oid  
lookupProcCallback(Oid profnoid, char promethod)
{
	Oid         result = InvalidOid;

	Insist(OidIsValid(profnoid));

	/* Lookup (profnoid, promethod) from index */

	/* (profnoid, promethod) is guaranteed unique by the index */

	result = caql_getoid(
			NULL,
			cql("SELECT procallback FROM pg_proc_callback "
				" WHERE profnoid = :1 "
				" AND promethod = :2 ",
				ObjectIdGetDatum(profnoid),
				CharGetDatum(promethod)));

	return result;
}