Don't dump core when destroying an unused ParallelContext.

robertmhaas · robertmhaas · commit 227d57f3587d · 2015-09-30T18:36:31.000-04:00
If a transaction or subtransaction creates a ParallelContext but ends
without calling InitializeParallelDSM, the previous code would
seg fault.  Fix that.
diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
@@ -513,14 +513,17 @@ DestroyParallelContext(ParallelContext *pcxt)
 	dlist_delete(&pcxt->node);
 
 	/* Kill each worker in turn, and forget their error queues. */
-	for (i = 0; i < pcxt->nworkers; ++i)
+	if (pcxt->worker != NULL)
 	{
-		if (pcxt->worker[i].bgwhandle != NULL)
-			TerminateBackgroundWorker(pcxt->worker[i].bgwhandle);
-		if (pcxt->worker[i].error_mqh != NULL)
+		for (i = 0; i < pcxt->nworkers; ++i)
 		{
-			pfree(pcxt->worker[i].error_mqh);
-			pcxt->worker[i].error_mqh = NULL;
+			if (pcxt->worker[i].bgwhandle != NULL)
+				TerminateBackgroundWorker(pcxt->worker[i].bgwhandle);
+			if (pcxt->worker[i].error_mqh != NULL)
+			{
+				pfree(pcxt->worker[i].error_mqh);
+				pcxt->worker[i].error_mqh = NULL;
+			}
 		}
 	}
 
@@ -550,7 +553,7 @@ DestroyParallelContext(ParallelContext *pcxt)
 	{
 		BgwHandleStatus status;
 
-		if (pcxt->worker[i].bgwhandle == NULL)
+		if (pcxt->worker == NULL || pcxt->worker[i].bgwhandle == NULL)
 			continue;
 
 		/*

Original file line number	Diff line number	Diff line change
`@@ -513,14 +513,17 @@ DestroyParallelContext(ParallelContext *pcxt)`
`513`	`513`	`dlist_delete(&pcxt->node);`
`514`	`514`
`515`	`515`	`/* Kill each worker in turn, and forget their error queues. */`
`516`		`- for (i = 0; i < pcxt->nworkers; ++i)`
	`516`	`+ if (pcxt->worker != NULL)`
`517`	`517`	`{`
`518`		`- if (pcxt->worker[i].bgwhandle != NULL)`
`519`		`- TerminateBackgroundWorker(pcxt->worker[i].bgwhandle);`
`520`		`- if (pcxt->worker[i].error_mqh != NULL)`
	`518`	`+ for (i = 0; i < pcxt->nworkers; ++i)`
`521`	`519`	`{`
`522`		`- pfree(pcxt->worker[i].error_mqh);`
`523`		`- pcxt->worker[i].error_mqh = NULL;`
	`520`	`+ if (pcxt->worker[i].bgwhandle != NULL)`
	`521`	`+ TerminateBackgroundWorker(pcxt->worker[i].bgwhandle);`
	`522`	`+ if (pcxt->worker[i].error_mqh != NULL)`
	`523`	`+ {`
	`524`	`+ pfree(pcxt->worker[i].error_mqh);`
	`525`	`+ pcxt->worker[i].error_mqh = NULL;`
	`526`	`+ }`
`524`	`527`	`}`
`525`	`528`	`}`
`526`	`529`
`@@ -550,7 +553,7 @@ DestroyParallelContext(ParallelContext *pcxt)`
`550`	`553`	`{`
`551`	`554`	`BgwHandleStatus status;`
`552`	`555`
`553`		`- if (pcxt->worker[i].bgwhandle == NULL)`
	`556`	`+ if (pcxt->worker == NULL \|\| pcxt->worker[i].bgwhandle == NULL)`
`554`	`557`	`continue;`
`555`	`558`
`556`	`559`	`/*`