Make EXPLAIN ANALYZE report the numbers of rows rejected by filter steps.

This provides information about the numbers of tuples that were visited
but not returned by table scans, as well as the numbers of join tuples
that were considered and discarded within a join plan node.

There is still some discussion going on about the best way to report counts
for outer-join situations, but I think most of what's in the patch would
not change if we revise that, so I'm going to go ahead and commit it as-is.

Documentation changes to follow (they weren't in the submitted patch
either).

Marko Tiikkaja, reviewed by Marc Cousin, somewhat revised by Tom

2 files changed, 20 insertions, 4 deletions

diff --git a/src/include/executor/instrument.h b/src/include/executor/instrument.h
index 286cd540632..22c31069436 100644
--- a/src/include/executor/instrument.h
+++ b/src/include/executor/instrument.h
@@ -28,6 +28,7 @@ typedef struct BufferUsage
 	long		temp_blks_written;		/* # of temp blocks written */
 } BufferUsage;
 
+/* Flag bits included in InstrAlloc's instrument_options bitmask */
 typedef enum InstrumentOption
 {
 	INSTRUMENT_TIMER = 1 << 0,	/* needs timer */
@@ -37,9 +38,10 @@ typedef enum InstrumentOption
 
 typedef struct Instrumentation
 {
+	/* Parameters set at node creation: */
+	bool		need_bufusage;	/* TRUE if we need buffer usage data */
 	/* Info about current plan cycle: */
 	bool		running;		/* TRUE if we've completed first tuple */
-	bool		needs_bufusage; /* TRUE if we need buffer usage */
 	instr_time	starttime;		/* Start time of current iteration of node */
 	instr_time	counter;		/* Accumulated runtime for this node */
 	double		firsttuple;		/* Time for first tuple of this cycle */
@@ -50,6 +52,8 @@ typedef struct Instrumentation
 	double		total;			/* Total total time (in seconds) */
 	double		ntuples;		/* Total tuples produced */
 	double		nloops;			/* # of run cycles for this node */
+	double		nfiltered1;		/* # tuples removed by scanqual or joinqual */
+	double		nfiltered2;		/* # tuples removed by "other" quals */
 	BufferUsage bufusage;		/* Total buffer usage */
 } Instrumentation;
 
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index b3eed7d189c..c8a0b598645 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -16,6 +16,7 @@
 
 #include "access/genam.h"
 #include "access/heapam.h"
+#include "executor/instrument.h"
 #include "nodes/params.h"
 #include "nodes/plannodes.h"
 #include "utils/reltrigger.h"
@@ -314,7 +315,7 @@ typedef struct ResultRelInfo
 	TriggerDesc *ri_TrigDesc;
 	FmgrInfo   *ri_TrigFunctions;
 	List	  **ri_TrigWhenExprs;
-	struct Instrumentation *ri_TrigInstrument;
+	Instrumentation *ri_TrigInstrument;
 	List	  **ri_ConstraintExprs;
 	JunkFilter *ri_junkFilter;
 	ProjectionInfo *ri_projectReturning;
@@ -967,8 +968,7 @@ typedef struct PlanState
 								 * nodes point to one EState for the whole
 								 * top-level plan */
 
-	struct Instrumentation *instrument; /* Optional runtime stats for this
-										 * plan node */
+	Instrumentation *instrument;	/* Optional runtime stats for this node */
 
 	/*
 	 * Common structural data for all Plan types.  These links to subsidiary
@@ -1008,6 +1008,18 @@ typedef struct PlanState
 #define innerPlanState(node)		(((PlanState *)(node))->righttree)
 #define outerPlanState(node)		(((PlanState *)(node))->lefttree)
 
+/* Macros for inline access to certain instrumentation counters */
+#define InstrCountFiltered1(node, delta) \
+	do { \
+		if (((PlanState *)(node))->instrument) \
+			((PlanState *)(node))->instrument->nfiltered1 += (delta); \
+	} while(0)
+#define InstrCountFiltered2(node, delta) \
+	do { \
+		if (((PlanState *)(node))->instrument) \
+			((PlanState *)(node))->instrument->nfiltered2 += (delta); \
+	} while(0)
+
 /*
  * EPQState is state for executing an EvalPlanQual recheck on a candidate
  * tuple in ModifyTable or LockRows.  The estate and planstate fields are