Prevent auto_explain from changing the output of a user's EXPLAIN.

Commit af7914c6, which introduced the
EXPLAIN (TIMING) option, for some reason coded explain.c to look at
planstate->instrument->need_timer rather than es->timing to decide
whether to print timing info.  However, the former flag might get set
as a result of contrib/auto_explain wanting timing information.  We
certainly don't want activation of auto_explain to change user-visible
statement behavior, so fix that.

Also fix an independent bug introduced in the same patch: in the code
path for a never-executed node with a machine-friendly output format,
if timing was selected, it would fail to print the Actual Rows and Actual
Loops items.

Per bug #10404 from Tomonari Katsumata.  Back-patch to 9.2 where the
faulty code was introduced.

src/backend/commands/explain.c

@@ -1184,11 +1184,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 	/*
 	 * We have to forcibly clean up the instrumentation state because we
 	 * haven't done ExecutorEnd yet.  This is pretty grotty ...
+	 *
+	 * Note: contrib/auto_explain could cause instrumentation to be set up
+	 * even though we didn't ask for it here.  Be careful not to print any
+	 * instrumentation results the user didn't ask for.  But we do the
+	 * InstrEndLoop call anyway, if possible, to reduce the number of cases
+	 * auto_explain has to contend with.
 	 */
 	if (planstate->instrument)
 		InstrEndLoop(planstate->instrument);
 
-	if (planstate->instrument && planstate->instrument->nloops > 0)
+	if (es->analyze &&
+		planstate->instrument && planstate->instrument->nloops > 0)
 	{
 		double		nloops = planstate->instrument->nloops;
 		double		startup_sec = 1000.0 * planstate->instrument->startup / nloops;
@@ -1197,7 +1204,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 
 		if (es->format == EXPLAIN_FORMAT_TEXT)
 		{
-			if (planstate->instrument->need_timer)
+			if (es->timing)
 				appendStringInfo(es->str,
 							" (actual time=%.3f..%.3f rows=%.0f loops=%.0f)",
 								 startup_sec, total_sec, rows, nloops);
@@ -1208,7 +1215,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		}
 		else
 		{
-			if (planstate->instrument->need_timer)
+			if (es->timing)
 			{
 				ExplainPropertyFloat("Actual Startup Time", startup_sec, 3, es);
 				ExplainPropertyFloat("Actual Total Time", total_sec, 3, es);
@@ -1219,20 +1226,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 	}
 	else if (es->analyze)
 	{
-
 		if (es->format == EXPLAIN_FORMAT_TEXT)
 			appendStringInfoString(es->str, " (never executed)");
-		else if (planstate->instrument->need_timer)
+		else
+		{
+			if (es->timing)
 			{
 				ExplainPropertyFloat("Actual Startup Time", 0.0, 3, es);
 				ExplainPropertyFloat("Actual Total Time", 0.0, 3, es);
 			}
-		else
-		{
 			ExplainPropertyFloat("Actual Rows", 0.0, 0, es);
 			ExplainPropertyFloat("Actual Loops", 0.0, 0, es);
 		}
-
 	}
 
 	/* in text format, first line ends here */
@@ -1426,7 +1431,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 	}
 
 	/* Show buffer usage */
-	if (es->buffers)
+	if (es->buffers && planstate->instrument)
 	{
 		const BufferUsage *usage = &planstate->instrument->bufusage;