fix_accum_instr_parallel_workers_v1.patch

diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c
index 53c5254..6a6bf20 100644
--- a/src/backend/executor/execParallel.c
+++ b/src/backend/executor/execParallel.c
@@ -919,14 +919,25 @@ ExecParallelRetrieveInstrumentation(PlanState *planstate,
 	 * regular instrumentation information, which is the per-query context.
 	 * Switch into per-query memory context.
 	 */
-	oldcontext = MemoryContextSwitchTo(planstate->state->es_query_cxt);
-	ibytes = mul_size(instrumentation->num_workers, sizeof(Instrumentation));
-	planstate->worker_instrument =
-		palloc(ibytes + offsetof(WorkerInstrumentation, instrument));
-	MemoryContextSwitchTo(oldcontext);
+	if (!planstate->worker_instrument)
+	{
+		oldcontext = MemoryContextSwitchTo(planstate->state->es_query_cxt);
+		ibytes = mul_size(instrumentation->num_workers, sizeof(Instrumentation));
+		planstate->worker_instrument =
+			palloc(ibytes + offsetof(WorkerInstrumentation, instrument));
+		MemoryContextSwitchTo(oldcontext);
+
+		for (n = 0; n < instrumentation->num_workers; ++n)
+			InstrInit(&planstate->worker_instrument->instrument[n],
+					  planstate->state->es_instrument);
+	}
 
 	planstate->worker_instrument->num_workers = instrumentation->num_workers;
-	memcpy(&planstate->worker_instrument->instrument, instrument, ibytes);
+
+	/* Accumulate the per-worker detail. */
+	for (n = 0; n < instrumentation->num_workers; ++n)
+		InstrAggNode(&planstate->worker_instrument->instrument[n],
+					 &instrument[n]);
 
 	/*
 	 * Perform any node-type-specific work that needs to be done.  Currently,
@@ -989,8 +1000,20 @@ ExecParallelFinish(ParallelExecutorInfo *pei)
 
 	/* Finally, accumulate instrumentation, if any. */
 	if (pei->instrumentation)
+	{
+		Instrumentation *instrument;
+		SharedExecutorInstrumentation *sh_instr;
+
+		sh_instr = pei->instrumentation;
+
 		ExecParallelRetrieveInstrumentation(pei->planstate,
-											pei->instrumentation);
+											sh_instr);
+
+		/* Clear the instrumentation space for next time. */
+		instrument = GetInstrumentationArray(sh_instr);
+		for (i = 0; i < sh_instr->num_workers * sh_instr->num_plan_nodes; ++i)
+			InstrInit(&instrument[i], pei->planstate->state->es_instrument);
+	}
 
 	pei->finished = true;
 }