Stop using a sequence to generate unique job IDs

src/backend/distributed/executor/multi_real_time_executor.c

@@ -225,8 +225,7 @@ MultiRealTimeExecute(Job *job)
 	 */
 	if (taskFailed)
 	{
-		ereport(ERROR, (errmsg("failed to execute job " UINT64_FORMAT, job->jobId),
+		ereport(ERROR, (errmsg("failed to execute task %u", failedTaskId)));
-						errdetail("Failure due to failed task %u", failedTaskId)));
 	}
 	else if (QueryCancelPending)
 	{

src/backend/distributed/executor/multi_task_tracker_executor.c

@@ -150,7 +150,6 @@ MultiTaskTrackerExecute(Job *job)
 	ListCell *taskAndExecutionCell = NULL;
 	uint32 taskTrackerCount = 0;
 	uint32 topLevelTaskCount = 0;
-	uint64 failedJobId = 0;
 	uint32 failedTaskId = 0;
 	bool allTasksCompleted = false;
 	bool taskFailed = false;
@@ -279,7 +278,6 @@ MultiTaskTrackerExecute(Job *job)
 			taskFailed = TaskExecutionFailed(taskExecution);
 			if (taskFailed)
 			{
-				failedJobId = taskExecution->jobId;
 				failedTaskId = taskExecution->taskId;
 				break;
 			}
@@ -336,7 +334,6 @@ MultiTaskTrackerExecute(Job *job)
 			taskTransmitFailed = TaskExecutionFailed(taskExecution);
 			if (taskTransmitFailed)
 			{
-				failedJobId = taskExecution->jobId;
 				failedTaskId = taskExecution->taskId;
 				break;
 			}
@@ -415,13 +412,11 @@ MultiTaskTrackerExecute(Job *job)
 	 */
 	if (taskFailed)
 	{
-		ereport(ERROR, (errmsg("failed to execute job " UINT64_FORMAT, failedJobId),
+		ereport(ERROR, (errmsg("failed to execute task %u", failedTaskId)));
-						errdetail("Failure due to failed task %u", failedTaskId)));
 	}
 	else if (clusterFailed)
 	{
-		ereport(ERROR, (errmsg("failed to execute job " UINT64_FORMAT, job->jobId),
+		ereport(ERROR, (errmsg("failed to execute task %u", failedTaskId)));
-						errdetail("Too many task tracker failures")));
 	}
 	else if (QueryCancelPending)
 	{

src/backend/distributed/planner/multi_physical_planner.c

@@ -22,6 +22,7 @@
 #include "access/heapam.h"
 #include "access/nbtree.h"
 #include "access/skey.h"
+#include "access/xlog.h"
 #include "catalog/pg_am.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_type.h"
@@ -63,6 +64,7 @@
 
 /* Policy to use when assigning tasks to worker nodes */
 int TaskAssignmentPolicy = TASK_ASSIGNMENT_GREEDY;
+bool EnableUniqueJobIds = true;
 
 
 /*
@@ -1693,41 +1695,61 @@ ChildNodeList(MultiNode *multiNode)
 
 /*
  * UniqueJobId allocates and returns a unique jobId for the job to be executed.
- * This allocation occurs both in shared memory and in write ahead logs; writing
- * to logs avoids the risk of having jobId collisions.
  *
- * Please note that the jobId sequence wraps around after 2^32 integers. This
+ * The resulting job ID is built up as:
- * leaves the upper 32-bits to slave nodes and their jobs.
+ * <16-bit group ID><24-bit process ID><1-bit secondary flag><23-bit local counter>
+ *
+ * When citus.enable_unique_job_ids is off then only the local counter is
+ * included to get repeatable results.
  */
 static uint64
 UniqueJobId(void)
 {
-	text *sequenceName = cstring_to_text(JOBID_SEQUENCE_NAME);
+	static uint32 jobIdCounter = 0;
-	Oid sequenceId = ResolveRelationId(sequenceName);
-	Datum sequenceIdDatum = ObjectIdGetDatum(sequenceId);
-	Datum jobIdDatum = 0;
-	int64 jobId = 0;
-	int64 localizedJobId = 0;
-	int64 localGroupId = GetLocalGroupId();
-	Oid savedUserId = InvalidOid;
-	int savedSecurityContext = 0;
 
-	GetUserIdAndSecContext(&savedUserId, &savedSecurityContext);
+	uint64 jobId = 0;
-	SetUserIdAndSecContext(CitusExtensionOwner(), SECURITY_LOCAL_USERID_CHANGE);
+	uint64 jobIdNumber = 0;
+	uint64 processId = 0;
+	uint64 localGroupId = 0;
 
-	/* generate new and unique jobId from sequence */
+	jobIdCounter++;
-	jobIdDatum = DirectFunctionCall1(nextval_oid, sequenceIdDatum);
-	jobId = DatumGetInt64(jobIdDatum);
 
+	if (EnableUniqueJobIds)
+	{
 		/*
 		 * Add the local group id information to the jobId to
 		 * prevent concurrent jobs on different groups to conflict.
 		 */
-	localizedJobId = jobId | (localGroupId << 32);
+		localGroupId = GetLocalGroupId() & 0xFF;
+		jobId = jobId | (localGroupId << 48);
 
-	SetUserIdAndSecContext(savedUserId, savedSecurityContext);
+		/*
+		 * Add the current process ID to distinguish jobs by this
+		 * backends from jobs started by other backends. Process
+		 * IDs can have at most 24-bits on platforms supported by
+		 * Citus.
+		 */
+		processId = MyProcPid & 0xFFFFFF;
+		jobId = jobId | (processId << 24);
 
-	return localizedJobId;
+		/*
+		 * Add an extra bit for secondaries to distinguish their
+		 * jobs from primaries.
+		 */
+		if (RecoveryInProgress())
+		{
+			jobId = jobId | (1 << 23);
+		}
+	}
+
+	/*
+	 * Use the remaining 23 bits to distinguish jobs by the
+	 * same backend.
+	 */
+	jobIdNumber = jobIdCounter & 0x1FFFFFF;
+	jobId = jobId | jobIdNumber;
+
+	return jobId;
 }
 
 
@@ -2144,8 +2166,7 @@ SubquerySqlTaskList(Job *job)
 		sqlTask->dependedTaskList = dataFetchTaskList;
 
 		/* log the query string we generated */
-		ereport(DEBUG4, (errmsg("generated sql query for job " UINT64_FORMAT
+		ereport(DEBUG4, (errmsg("generated sql query for task %d", sqlTask->taskId),
-								" and task %d", sqlTask->jobId, sqlTask->taskId),
 						 errdetail("query string: \"%s\"", sqlQueryString->data)));
 
 		sqlTask->anchorShardId = AnchorShardId(fragmentCombination, anchorRangeTableId);
@@ -2260,8 +2281,7 @@ SqlTaskList(Job *job)
 		sqlTask->dependedTaskList = dataFetchTaskList;
 
 		/* log the query string we generated */
-		ereport(DEBUG4, (errmsg("generated sql query for job " UINT64_FORMAT
+		ereport(DEBUG4, (errmsg("generated sql query for task %d", sqlTask->taskId),
-								" and task %d", sqlTask->jobId, sqlTask->taskId),
 						 errdetail("query string: \"%s\"", sqlQueryString->data)));
 
 		sqlTask->anchorShardId = INVALID_SHARD_ID;

src/backend/distributed/shared_library_init.c

@@ -634,6 +634,18 @@ RegisterCitusConfigVariables(void)
 		GUC_NO_SHOW_ALL,
 		NULL, NULL, NULL);
 
+	DefineCustomBoolVariable(
+		"citus.enable_unique_job_ids",
+		gettext_noop("Enables unique job IDs by prepending the local process ID and "
+					 "group ID. This should usually be enabled, but can be disabled "
+					 "for repeatable output in regression tests."),
+		NULL,
+		&EnableUniqueJobIds,
+		true,
+		PGC_USERSET,
+		GUC_SUPERUSER_ONLY | GUC_NO_SHOW_ALL,
+		NULL, NULL, NULL);
+
 	/* warn about config items in the citus namespace that are not registered above */
 	EmitWarningsOnPlaceholders("citus");
 }

src/include/distributed/multi_physical_planner.h

@@ -28,7 +28,6 @@
 
 
 /* Definitions local to the physical planner */
-#define JOBID_SEQUENCE_NAME "pg_dist_jobid_seq"
 #define ARRAY_OUT_FUNC_ID 751
 #define NON_PRUNABLE_JOIN -1
 #define RESERVED_HASHED_COLUMN_ID MaxAttrNumber
@@ -244,6 +243,8 @@ typedef struct OperatorCacheEntry
 
 /* Config variable managed via guc.c */
 extern int TaskAssignmentPolicy;
+extern bool EnableUniqueJobIds;
+
 
 /* Function declarations for building physical plans and constructing queries */
 extern MultiPlan * MultiPhysicalPlanCreate(MultiTreeRoot *multiTree);