Remove gp_cancel_query() and friends.

The upstream pg_cancel_backend() function should work fine on GPDB. It's
not exactly the same: in gp_cancel_query(), you would pass the sesssion ID
and command ID as argument, while pg_cancel_backend() takes a PID. But it
seems just as good from a usability point of view. Let's avoid the
duplicate code, and remove gp_cancel_query().

Also remove the gp_cancel_query_print_log and gp_cancel_query_delay_time
GUCs. They were not directly related to gp_cancel_query() - they would
have an effect on cancellations caused by pg_cancel_backend() or
statement_timeout, too. But they were marked as "developer options", and
they printed the session and command ID so I think they were meant to be
used with gp_cancel_backend(). I don't think anyone uses them, though, so
let's just remove them, rather than change them to print PIDs.

GNUmakefile.in

@@ -22,7 +22,6 @@ all:
 	$(MAKE) -C contrib/gp_distribution_policy all
 	$(MAKE) -C contrib/gp_inject_fault all
 	$(MAKE) -C contrib/gp_internal_tools all
-	$(MAKE) -C contrib/gp_cancel_query all
 	$(MAKE) -C contrib/indexscan all
 	$(MAKE) -C contrib/pg_upgrade_support all
 	$(MAKE) -C contrib/pg_upgrade all
@@ -58,7 +57,6 @@ install:
 	$(MAKE) -C contrib/gp_distribution_policy $@
 	$(MAKE) -C contrib/gp_inject_fault $@
 	$(MAKE) -C contrib/gp_internal_tools $@
-	$(MAKE) -C contrib/gp_cancel_query $@
 	$(MAKE) -C contrib/indexscan $@ 
 	$(MAKE) -C contrib/pg_upgrade_support $@
 	$(MAKE) -C contrib/pg_upgrade $@

contrib/Makefile

@@ -55,7 +55,6 @@ SUBDIRS += \
 		gp_distribution_policy \
 		gp_internal_tools \
 		gp_inject_fault \
-		gp_cancel_query \
 		gp_sparse_vector \
 		indexscan \
 

contrib/gp_cancel_query/Makefile

-MODULE_big = gp_cancel_query
-OBJS       = gp_cancel_query.o
-
-PG_CPPFLAGS = -I$(libpq_srcdir)
-
-ifdef USE_PGXS
-PGXS := $(shell pg_config --pgxs)
-include $(PGXS)
-else
-subdir = contrib/gp_cancel_query
-top_builddir = ../..
-include $(top_builddir)/src/Makefile.global
-include $(top_srcdir)/contrib/contrib-global.mk
-endif

contrib/gp_cancel_query/gp_cancel_query.c

-/*
- * Copyright (c) 2011 EMC Corporation All Rights Reserved
- *
- * This software is protected, without limitation, by copyright law
- * and international treaties. Use of this software and the intellectual
- * property contained therein is expressly limited to the terms and
- * conditions of the License Agreement under which it is provided by
- * or on behalf of EMC.
- *
- * ---------------------------------------------------------------------
- *
- * Interface to gp_cancel_query_wrapper function.
- *
- * The gp_cancel_query_wrapper function is a wrapper around the gp_cancel_query
- * function located in the postgres backend executable. Since we can not call the
- * gp_cancel_query function directly without a change to the catalog tables, this
- * wrapper will allow a user to create a function using this wrapper and indirectly
- * call gp_cancel_query.
- *
- * The dynamicly linked library created from this source can be reference by
- * creating a function in psql that references it. For example,
- *
- * CREATE OR REPLACE FUNCTION gp_cancel_query(int, int)
- *   RETURNS bool
- *   AS '$libdir/gp_cancel_query.so', 'gp_cancel_query_wrapper' LANGUAGE C STRICT;
- *
- */
-
-#include "postgres.h"
-#include <string.h>
-#include "fmgr.h"
-#include "funcapi.h"
-#include "utils/builtins.h"
-
-#ifdef PG_MODULE_MAGIC
-PG_MODULE_MAGIC;
-#endif
-
-extern Datum gp_cancel_query(PG_FUNCTION_ARGS);
-
-PG_FUNCTION_INFO_V1(gp_cancel_query_wrapper);
-
-extern Datum gp_cancel_query_wrapper(PG_FUNCTION_ARGS);
-
-/*
- * gp_cancel_query_wrapper
- *    The wrapper for creating a user-defined C function for gp_cancel_query.
- */
-Datum
-gp_cancel_query_wrapper(PG_FUNCTION_ARGS)
-{
-	return gp_cancel_query(fcinfo);
-}
-

src/backend/cdb/cdbvars.c

@@ -760,14 +760,6 @@ gpvars_check_statement_mem(int *newval, void **extra, GucSource source)
 void
 increment_command_count()
 {
-	if (gp_cancel_query_print_log)
-	{
-		ereport(LOG,
-				(errmsg("Incrementing command count from %d to %d",
-						gp_command_count, gp_command_count + 1),
-				 errprintstack(true)));
-	}
-
 	gp_command_count++;
 	if (gp_command_count <= 0)
 	{

src/backend/executor/execUtils.c

@@ -2372,23 +2372,6 @@ void mppExecutorCleanup(QueryDesc *queryDesc)
 		QueryCancelCleanup)
 	{			
 		gpmon_qlog_query_canceling(queryDesc->gpmon_pkt);
-
-		if (gp_cancel_query_print_log)
-		{
-			elog(LOG, "canceling query (%d, %d)",
-				 queryDesc->gpmon_pkt->u.qlog.key.ssid,
-				 queryDesc->gpmon_pkt->u.qlog.key.ccnt);
-		}
-	}
-
-	/*
-	 * Delaying the cancellation for a specified time.
-	 */
-	if (Gp_role == GP_ROLE_DISPATCH &&
-		QueryCancelCleanup &&
-		gp_cancel_query_delay_time > 0)
-	{
-		pg_usleep(gp_cancel_query_delay_time * 1000);
 	}
 
 	/*

src/backend/storage/ipc/procarray.c

@@ -3672,55 +3672,6 @@ FindProcByGpSessionId(long gp_session_id)
 	return NULL;
 }
 
-/*
- * FindAndSignalProcess
- *     Find the PGPROC entry in procArray which contains the given sessionId and commandId,
- *     and send the corresponding process an interrupt signal.
- *
- * This function returns false if not such an entry found in procArray or the interrupt
- * signal can not be sent to the process.
- */
-bool
-FindAndSignalProcess(int sessionId, int commandId)
-{
-	Assert(sessionId > 0 && commandId > 0);
-	bool queryCancelled = false;
-	int pid = 0;
-
-	LWLockAcquire(ProcArrayLock, LW_SHARED);
-
-	for (int index = 0; index < procArray->numProcs; index++)
-	{
-		PGPROC *proc = &allProcs[procArray->pgprocnos[index]];
-		
-		if (proc->mppSessionId == sessionId &&
-			proc->queryCommandId == commandId)
-		{
-			/* If we have setsid(), signal the backend's whole process group */
-#ifdef HAVE_SETSID
-			if (kill(-proc->pid, SIGINT) == 0)
-#else
-			if (kill(proc->pid, SIGINT) == 0)
-#endif
-			{
-				pid = proc->pid;
-				queryCancelled = true;
-			}
-			
-			break;
-		}
-	}
-
-	LWLockRelease(ProcArrayLock);
-
-	if (gp_cancel_query_print_log && queryCancelled)
-	{
-		elog(NOTICE, "sent an interrupt to process %d", pid);
-	}
-
-	return queryCancelled;
-}
-
 /* ----------------------------------------------
  *		KnownAssignedTransactions sub-module
  * ----------------------------------------------

src/backend/storage/lmgr/proc.c

@@ -493,8 +493,6 @@ InitProcess(void)
 	/* Set wait portal (do not check if resource scheduling is enabled) */
 	MyProc->waitPortalId = INVALID_PORTALID;
 
-	MyProc->queryCommandId = -1;
-
 	/* Init gxact */
 	initGxact(MyTmGxact);
 
@@ -653,8 +651,6 @@ InitAuxiliaryProcess(void)
 	 */
 	PGSemaphoreReset(&MyProc->sem);
 
-	MyProc->queryCommandId = -1;
-
 	/*
 	 * Arrange to clean up at process exit.
 	 */

src/backend/tcop/postgres.c

@@ -1558,17 +1558,8 @@ exec_simple_query(const char *query_string)
 	char		msec_str[32];
 
 	if (Gp_role != GP_ROLE_EXECUTE)
-	{
 		increment_command_count();
 
-		MyProc->queryCommandId = gp_command_count;
-		if (gp_cancel_query_print_log)
-		{
-			elog(NOTICE, "running query (sessionId, commandId): (%d, %d)",
-				 MyProc->mppSessionId, gp_command_count);
-		}
-	}
-
 	/*
 	 * Report query to various monitoring facilities.
 	 */
@@ -2621,24 +2612,7 @@ exec_execute_message(const char *portal_name, int64 max_rows)
 			}
 		}
 		if (is_utility_stmt)
-		{
 			increment_command_count();
-
-			MyProc->queryCommandId = gp_command_count;
-			if (gp_cancel_query_print_log)
-			{
-				elog(NOTICE, "running query (sessionId, commandId): (%d, %d)",
-						MyProc->mppSessionId, gp_command_count);
-				elog(LOG, "In exec_execute_message found utility statement, incrementing command_count");
-			}
-		}
-		else
-		{
-			if (gp_cancel_query_print_log)
-			{
-				elog(LOG, "In exec_execute_message found non-utility statement, NOT incrementing command count");
-			}
-		}
 	}
 
 	/* Does the portal contain a transaction command? */

src/backend/tcop/pquery.c

@@ -114,17 +114,8 @@ CreateQueryDesc(PlannedStmt *plannedstmt,
 	qd->gpmon_pkt = NULL;
 	
 	if (Gp_role != GP_ROLE_EXECUTE)
-	{
 		increment_command_count();
 
-		MyProc->queryCommandId = gp_command_count;
-		if (gp_cancel_query_print_log)
-		{
-			elog(NOTICE, "running query (sessionId, commandId): (%d, %d)",
-				 MyProc->mppSessionId, gp_command_count);
-		}
-	}
-	
 	if(gp_enable_gpperfmon && Gp_role == GP_ROLE_DISPATCH)
 	{
 		qd->gpmon_pkt = (gpmon_packet_t *) palloc0(sizeof(gpmon_packet_t));

src/backend/utils/adt/misc.c

@@ -219,60 +219,6 @@ pg_terminate_backend_msg(PG_FUNCTION_ARGS)
 	PG_RETURN_BOOL(pg_signal_backend(pid, SIGTERM, msg) == SIGNAL_BACKEND_SUCCESS);
 }
 
-/*
- * gp_cancel_query_internal
- *    Cancel the query that is identified by (sessionId, commandId) pair.
- *
- * This function errors out if this is called by non-super user.
- * This function prints a warning and returns false when (sessionId, commandId) does not
- * exist.
- *
- * In all other cases, this function finds the process id from procArray, and sends
- * an interrupt signal to the process.
- */
-static bool
-gp_cancel_query_internal(int sessionId, int commandId)
-{
-	if (!superuser())
-	{
-		ereport(ERROR,
-				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 (errmsg("must be superuser to cancel a query"))));
-	}
-
-	if (!(sessionId > 0 && commandId > 0))
-	{
-		ereport(WARNING, 
-				(errcode(ERRCODE_WARNING),
-				 errmsg("invalid session_id or command_id for query (session_id, command_id): (%d, %d)",
-						DatumGetInt32(sessionId), DatumGetInt32(commandId))));
-		return false;
-	}
-
-	bool succeed = FindAndSignalProcess(sessionId, commandId);
-	if (!succeed)
-	{
-		ereport(WARNING, 
-				(errcode(ERRCODE_WARNING),
-				 errmsg("failed to cancel query (session_id, command_id): (%d, %d)",
-						DatumGetInt32(sessionId), DatumGetInt32(commandId))));
-		return false;
-	}
-
-	return true;
-}
-
-/*
- * gp_cancel_query
- *    Cancel the query that is identified by (sessionId, commandId) pair.
- */
-Datum
-gp_cancel_query(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_BOOL(gp_cancel_query_internal(PG_GETARG_INT32(0),
-											PG_GETARG_INT32(1)));
-}
-
 /*
  * Signal to reload the database configuration
  */

src/backend/utils/misc/guc_gp.c

@@ -280,9 +280,6 @@ int			gp_test_time_slice_report_level = ERROR;
 bool		gp_test_deadlock_hazard;
 int			gp_test_deadlock_hazard_report_level = ERROR;
 
-/* query cancellation GUC */
-bool		gp_cancel_query_print_log;
-int			gp_cancel_query_delay_time;
 bool		vmem_process_interrupt = false;
 bool		execute_pruned_plan = false;
 
@@ -1982,17 +1979,6 @@ struct config_bool ConfigureNamesBool_gp[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"gp_cancel_query_print_log", PGC_USERSET, DEVELOPER_OPTIONS,
-			gettext_noop("Print out debugging info for a canceled query"),
-			NULL,
-			GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE | GUC_GPDB_ADDOPT
-		},
-		&gp_cancel_query_print_log,
-		false,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"gp_partitioning_dynamic_selection_log", PGC_USERSET, DEVELOPER_OPTIONS,
 			gettext_noop("Print out debugging info for GPDB dynamic partition selection"),
@@ -3078,17 +3064,6 @@ struct config_int ConfigureNamesInt_gp[] =
 		NULL, NULL, NULL
 	},
 
-	{
-		{"gp_cancel_query_delay_time", PGC_USERSET, DEVELOPER_OPTIONS,
-			gettext_noop("The time in milliseconds to delay a query cancellation."),
-			NULL,
-			GUC_UNIT_MS | GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE | GUC_GPDB_ADDOPT
-		},
-		&gp_cancel_query_delay_time,
-		0, 0, INT_MAX,
-		NULL, NULL, NULL
-	},
-
 	{
 		{"gp_max_local_distributed_cache", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Sets the number of local-distributed transactions to cache for optimizing visibility processing by backends."),

src/include/storage/proc.h

@@ -166,8 +166,6 @@ struct PGPROC
 	 */
 	uint32		combocid_map_count; /* how many entries in the map ? */
 
-	int queryCommandId; /* command_id for the running query */
-
 	bool serializableIsoLevel; /* true if proc has serializable isolation level set */
 
 	/*

src/include/storage/procarray.h

@@ -90,8 +90,6 @@ extern void updateSharedLocalSnapshot(struct DtxContextInfo *dtxContextInfo, str
 
 extern void GetSlotTableDebugInfo(void **snapshotArray, int *maxSlots);
 
-extern bool FindAndSignalProcess(int sessionId, int commandId);
-
 extern void getDtxCheckPointInfo(char **result, int *result_size);
 
 extern List *ListAllGxid(void);

src/include/utils/builtins.h

@@ -503,7 +503,6 @@ extern Datum pg_cancel_backend(PG_FUNCTION_ARGS);
 extern Datum pg_terminate_backend(PG_FUNCTION_ARGS);
 extern Datum pg_cancel_backend_msg(PG_FUNCTION_ARGS);
 extern Datum pg_terminate_backend_msg(PG_FUNCTION_ARGS);
-extern Datum gp_cancel_query(PG_FUNCTION_ARGS);
 extern Datum pg_reload_conf(PG_FUNCTION_ARGS);
 extern Datum pg_tablespace_databases(PG_FUNCTION_ARGS);
 extern Datum pg_tablespace_location(PG_FUNCTION_ARGS);

src/include/utils/guc.h

@@ -322,8 +322,6 @@ extern int	temp_file_limit;
 
 extern int	num_temp_buffers;
 
-extern bool gp_cancel_query_print_log;
-extern int gp_cancel_query_delay_time;
 extern bool vmem_process_interrupt;
 extern bool execute_pruned_plan;