From 2bb1f14b89deacd1142b4a06bcb1a52a76270449 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 13 Jan 2014 14:42:16 -0500
Subject: [PATCH] Make bitmap heap scans show exact/lossy block info in EXPLAIN
 ANALYZE.

Etsuro Fujita
---
 src/backend/commands/explain.c            | 33 ++++++++++++++++++++++-
 src/backend/executor/nodeBitmapHeapscan.c |  7 +++++
 src/include/nodes/execnodes.h             |  4 +++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 7097eff9b11..e604be31f9d 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -85,6 +85,8 @@ static void show_sort_group_keys(PlanState *planstate, const char *qlabel,
 					 List *ancestors, ExplainState *es);
 static void show_sort_info(SortState *sortstate, ExplainState *es);
 static void show_hash_info(HashState *hashstate, ExplainState *es);
+static void show_tidbitmap_info(BitmapHeapScanState *planstate,
+								ExplainState *es);
 static void show_instrumentation_count(const char *qlabel, int which,
 						   PlanState *planstate, ExplainState *es);
 static void show_foreignscan_info(ForeignScanState *fsstate, ExplainState *es);
@@ -1250,7 +1252,13 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (((BitmapHeapScan *) plan)->bitmapqualorig)
 				show_instrumentation_count("Rows Removed by Index Recheck", 2,
 										   planstate, es);
-			/* FALL THRU */
+			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
+			if (es->analyze)
+				show_tidbitmap_info((BitmapHeapScanState *) planstate, es);
+			break;
 		case T_SeqScan:
 		case T_ValuesScan:
 		case T_CteScan:
@@ -1878,6 +1886,29 @@ show_hash_info(HashState *hashstate, ExplainState *es)
 	}
 }
 
+/*
+ * If it's EXPLAIN ANALYZE, show exact/lossy pages for a BitmapHeapScan node
+ */
+static void
+show_tidbitmap_info(BitmapHeapScanState *planstate, ExplainState *es)
+{
+	if (es->format != EXPLAIN_FORMAT_TEXT)
+	{
+		ExplainPropertyLong("Exact Heap Blocks", planstate->exact_pages, es);
+		ExplainPropertyLong("Lossy Heap Blocks", planstate->lossy_pages, es);
+	}
+	else
+	{
+		appendStringInfoSpaces(es->str, es->indent * 2);
+		appendStringInfoString(es->str, "Heap Blocks:");
+		if (planstate->exact_pages > 0)
+			appendStringInfo(es->str, " exact=%ld", planstate->exact_pages);
+		if (planstate->lossy_pages > 0)
+			appendStringInfo(es->str, " lossy=%ld", planstate->lossy_pages);
+		appendStringInfoChar(es->str, '\n');
+	}
+}
+
 /*
  * If it's EXPLAIN ANALYZE, show instrumentation information for a plan node
  *
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index 3d98c2335c1..1a8d4e51430 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -170,6 +170,11 @@ BitmapHeapNext(BitmapHeapScanState *node)
 			 */
 			bitgetpage(scan, tbmres);
 
+			if (tbmres->ntuples >= 0)
+				node->exact_pages++;
+			else
+				node->lossy_pages++;
+
 			/*
 			 * Set rs_cindex to first slot to examine
 			 */
@@ -553,6 +558,8 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
 	scanstate->tbm = NULL;
 	scanstate->tbmiterator = NULL;
 	scanstate->tbmres = NULL;
+	scanstate->exact_pages = 0;
+	scanstate->lossy_pages = 0;
 	scanstate->prefetch_iterator = NULL;
 	scanstate->prefetch_pages = 0;
 	scanstate->prefetch_target = 0;
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 94ab0f2a933..a301a08fba9 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1338,6 +1338,8 @@ typedef struct BitmapIndexScanState
  *		tbm				   bitmap obtained from child index scan(s)
  *		tbmiterator		   iterator for scanning current pages
  *		tbmres			   current-page data
+ *		exact_pages		   total number of exact pages retrieved
+ *		lossy_pages		   total number of lossy pages retrieved
  *		prefetch_iterator  iterator for prefetching ahead of current page
  *		prefetch_pages	   # pages prefetch iterator is ahead of current
  *		prefetch_target    target prefetch distance
@@ -1350,6 +1352,8 @@ typedef struct BitmapHeapScanState
 	TIDBitmap  *tbm;
 	TBMIterator *tbmiterator;
 	TBMIterateResult *tbmres;
+	long		exact_pages;
+	long		lossy_pages;
 	TBMIterator *prefetch_iterator;
 	int			prefetch_pages;
 	int			prefetch_target;
-- 
2.30.2