Don't dump core when destroying an unused ParallelContext.

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
index f4ba8518b1215d218dc1b8561f6ad83fe9f9bdc5..29d6ed57cc251b290104c3a8faae5ab3c8302567 100644 (file)
--- 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;
 
        /*