When passing query strings to workers, pass the terminating \0.

Otherwise, when the query string is read, we might trailing garbage
beyond the end, unless there happens to be a \0 there by good luck.

Report and patch by Thomas Munro. Reviewed by Rafia Sabih.

Discussion: http://postgr.es/m/CAEepm=2SJs7X+_vx8QoDu8d1SMEOxtLhxxLNzZun_BvNkuNhrw@mail.gmail.com

src/backend/executor/execParallel.c

@@ -597,7 +597,7 @@ ExecInitParallelPlan(PlanState *planstate, EState *estate,
 
 	/* Estimate space for query text. */
 	query_len = strlen(estate->es_sourceText);
-	shm_toc_estimate_chunk(&pcxt->estimator, query_len);
+	shm_toc_estimate_chunk(&pcxt->estimator, query_len + 1);
 	shm_toc_estimate_keys(&pcxt->estimator, 1);
 
 	/* Estimate space for serialized PlannedStmt. */
@@ -672,8 +672,8 @@ ExecInitParallelPlan(PlanState *planstate, EState *estate,
 	shm_toc_insert(pcxt->toc, PARALLEL_KEY_EXECUTOR_FIXED, fpes);
 
 	/* Store query string */
-	query_string = shm_toc_allocate(pcxt->toc, query_len);
-	memcpy(query_string, estate->es_sourceText, query_len);
+	query_string = shm_toc_allocate(pcxt->toc, query_len + 1);
+	memcpy(query_string, estate->es_sourceText, query_len + 1);
 	shm_toc_insert(pcxt->toc, PARALLEL_KEY_QUERY_TEXT, query_string);
 
 	/* Store serialized PlannedStmt. */