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

src/backend/commands/explain.c

@@ -18,7 +18,6 @@
 #include "commands/defrem.h"
 #include "commands/prepare.h"
 #include "executor/hashjoin.h"
-#include "executor/instrument.h"
 #include "foreign/fdwapi.h"
 #include "optimizer/clauses.h"
 #include "parser/parsetree.h"
@@ -76,6 +75,8 @@ static void show_sort_keys_common(PlanState *planstate,
 					  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_instrumentation_count(const char *qlabel, int which,
+						   PlanState *planstate, ExplainState *es);
 static void show_foreignscan_info(ForeignScanState *fsstate, ExplainState *es);
 static const char *explain_get_index_name(Oid indexId);
 static void ExplainScanTarget(Scan *plan, ExplainState *es);
@@ -1000,9 +1001,15 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_IndexScan:
 			show_scan_qual(((IndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
+			if (((IndexScan *) plan)->indexqualorig)
+				show_instrumentation_count("Rows Removed by Index Recheck", 2,
+										   planstate, es);
 			show_scan_qual(((IndexScan *) plan)->indexorderbyorig,
 						   "Order By", planstate, ancestors, es);
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
 			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
@@ -1011,6 +1018,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_BitmapHeapScan:
 			show_scan_qual(((BitmapHeapScan *) plan)->bitmapqualorig,
 						   "Recheck Cond", planstate, ancestors, es);
+			if (((BitmapHeapScan *) plan)->bitmapqualorig)
+				show_instrumentation_count("Rows Removed by Index Recheck", 2,
+										   planstate, es);
 			/* FALL THRU */
 		case T_SeqScan:
 		case T_ValuesScan:
@@ -1018,6 +1028,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_SubqueryScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
 			break;
 		case T_FunctionScan:
 			if (es->verbose)
@@ -1025,6 +1038,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 								"Function Call", planstate, ancestors,
 								es->verbose, es);
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
 			break;
 		case T_TidScan:
 			{
@@ -1038,34 +1054,61 @@ ExplainNode(PlanState *planstate, List *ancestors,
 					tidquals = list_make1(make_orclause(tidquals));
 				show_scan_qual(tidquals, "TID Cond", planstate, ancestors, es);
 				show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+				if (plan->qual)
+					show_instrumentation_count("Rows Removed by Filter", 1,
+											   planstate, es);
 			}
 			break;
 		case T_ForeignScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
 			show_foreignscan_info((ForeignScanState *) planstate, es);
 			break;
 		case T_NestLoop:
 			show_upper_qual(((NestLoop *) plan)->join.joinqual,
 							"Join Filter", planstate, ancestors, es);
+			if (((NestLoop *) plan)->join.joinqual)
+				show_instrumentation_count("Rows Removed by Join Filter", 1,
+										   planstate, es);
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 2,
+										   planstate, es);
 			break;
 		case T_MergeJoin:
 			show_upper_qual(((MergeJoin *) plan)->mergeclauses,
 							"Merge Cond", planstate, ancestors, es);
 			show_upper_qual(((MergeJoin *) plan)->join.joinqual,
 							"Join Filter", planstate, ancestors, es);
+			if (((MergeJoin *) plan)->join.joinqual)
+				show_instrumentation_count("Rows Removed by Join Filter", 1,
+										   planstate, es);
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 2,
+										   planstate, es);
 			break;
 		case T_HashJoin:
 			show_upper_qual(((HashJoin *) plan)->hashclauses,
 							"Hash Cond", planstate, ancestors, es);
 			show_upper_qual(((HashJoin *) plan)->join.joinqual,
 							"Join Filter", planstate, ancestors, es);
+			if (((HashJoin *) plan)->join.joinqual)
+				show_instrumentation_count("Rows Removed by Join Filter", 1,
+										   planstate, es);
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 2,
+										   planstate, es);
 			break;
 		case T_Agg:
 		case T_Group:
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
 			break;
 		case T_Sort:
 			show_sort_keys((SortState *) planstate, ancestors, es);
@@ -1079,6 +1122,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			show_upper_qual((List *) ((Result *) plan)->resconstantqual,
 							"One-Time Filter", planstate, ancestors, es);
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
 			break;
 		case T_Hash:
 			show_hash_info((HashState *) planstate, es);
@@ -1508,6 +1554,37 @@ show_hash_info(HashState *hashstate, ExplainState *es)
 	}
 }
 
+/*
+ * If it's EXPLAIN ANALYZE, show instrumentation information for a plan node
+ *
+ * "which" identifies which instrumentation counter to print
+ */
+static void
+show_instrumentation_count(const char *qlabel, int which,
+						   PlanState *planstate, ExplainState *es)
+{
+	double		nfiltered;
+	double		nloops;
+
+	if (!es->analyze || !planstate->instrument)
+		return;
+
+	if (which == 2)
+		nfiltered = planstate->instrument->nfiltered2;
+	else
+		nfiltered = planstate->instrument->nfiltered1;
+	nloops = planstate->instrument->nloops;
+
+	/* In text mode, suppress zero counts; they're not interesting enough */
+	if (nfiltered > 0 || es->format != EXPLAIN_FORMAT_TEXT)
+	{
+		if (nloops > 0)
+			ExplainPropertyFloat(qlabel, nfiltered / nloops, 0, es);
+		else
+			ExplainPropertyFloat(qlabel, 0.0, 0, es);
+	}
+}
+
 /*
  * Show extra information for a ForeignScan node.
  */

src/backend/commands/trigger.c

@@ -29,7 +29,6 @@
 #include "commands/defrem.h"
 #include "commands/trigger.h"
 #include "executor/executor.h"
-#include "executor/instrument.h"
 #include "miscadmin.h"
 #include "nodes/bitmapset.h"
 #include "nodes/makefuncs.h"

src/backend/executor/execAmi.c

@@ -13,7 +13,6 @@
 #include "postgres.h"
 
 #include "executor/execdebug.h"
-#include "executor/instrument.h"
 #include "executor/nodeAgg.h"
 #include "executor/nodeAppend.h"
 #include "executor/nodeBitmapAnd.h"

src/backend/executor/execMain.c

@@ -47,7 +47,6 @@
 #include "commands/tablespace.h"
 #include "commands/trigger.h"
 #include "executor/execdebug.h"
-#include "executor/instrument.h"
 #include "miscadmin.h"
 #include "optimizer/clauses.h"
 #include "parser/parse_clause.h"

src/backend/executor/execProcnode.c

@@ -77,7 +77,6 @@
 #include "postgres.h"
 
 #include "executor/executor.h"
-#include "executor/instrument.h"
 #include "executor/nodeAgg.h"
 #include "executor/nodeAppend.h"
 #include "executor/nodeBitmapAnd.h"

src/backend/executor/execScan.c

@@ -219,6 +219,8 @@ ExecScan(ScanState *node,
 				return slot;
 			}
 		}
+		else
+			InstrCountFiltered1(node, 1);
 
 		/*
 		 * Tuple fails qual, so free per-tuple memory and try again.

src/backend/executor/instrument.c

@@ -22,6 +22,7 @@ BufferUsage pgBufferUsage;
 static void BufferUsageAccumDiff(BufferUsage *dst,
 					 const BufferUsage *add, const BufferUsage *sub);
 
+
 /* Allocate new instrumentation structure(s) */
 Instrumentation *
 InstrAlloc(int n, int instrument_options)
@@ -31,13 +32,14 @@ InstrAlloc(int n, int instrument_options)
 	/* timer is always required for now */
 	Assert(instrument_options & INSTRUMENT_TIMER);
 
+	/* initialize all fields to zeroes, then modify as needed */
 	instr = palloc0(n * sizeof(Instrumentation));
 	if (instrument_options & INSTRUMENT_BUFFERS)
 	{
 		int			i;
 
 		for (i = 0; i < n; i++)
-			instr[i].needs_bufusage = true;
+			instr[i].need_bufusage = true;
 	}
 
 	return instr;
@@ -52,8 +54,8 @@ InstrStartNode(Instrumentation *instr)
 	else
 		elog(DEBUG2, "InstrStartNode called twice in a row");
 
-	/* initialize buffer usage per plan node */
-	if (instr->needs_bufusage)
+	/* save buffer usage totals at node entry, if needed */
+	if (instr->need_bufusage)
 		instr->bufusage_start = pgBufferUsage;
 }
 
@@ -77,8 +79,8 @@ InstrStopNode(Instrumentation *instr, double nTuples)
 
 	INSTR_TIME_SET_ZERO(instr->starttime);
 
-	/* Adds delta of buffer usage to node's count. */
-	if (instr->needs_bufusage)
+	/* Add delta of buffer usage since entry to node's totals */
+	if (instr->need_bufusage)
 		BufferUsageAccumDiff(&instr->bufusage,
 							 &pgBufferUsage, &instr->bufusage_start);
 
@@ -119,12 +121,12 @@ InstrEndLoop(Instrumentation *instr)
 	instr->tuplecount = 0;
 }
 
+/* dst += add - sub */
 static void
 BufferUsageAccumDiff(BufferUsage *dst,
 					 const BufferUsage *add,
 					 const BufferUsage *sub)
 {
-	/* dst += add - sub */
 	dst->shared_blks_hit += add->shared_blks_hit - sub->shared_blks_hit;
 	dst->shared_blks_read += add->shared_blks_read - sub->shared_blks_read;
 	dst->shared_blks_written += add->shared_blks_written - sub->shared_blks_written;

src/backend/executor/nodeAgg.c

@@ -1204,6 +1204,8 @@ agg_retrieve_direct(AggState *aggstate)
 				return result;
 			}
 		}
+		else
+			InstrCountFiltered1(aggstate, 1);
 	}
 
 	/* No more groups */
@@ -1354,6 +1356,8 @@ agg_retrieve_hash_table(AggState *aggstate)
 				return result;
 			}
 		}
+		else
+			InstrCountFiltered1(aggstate, 1);
 	}
 
 	/* No more groups */

src/backend/executor/nodeBitmapAnd.c

@@ -29,7 +29,6 @@
 #include "postgres.h"
 
 #include "executor/execdebug.h"
-#include "executor/instrument.h"
 #include "executor/nodeBitmapAnd.h"
 
 

src/backend/executor/nodeBitmapHeapscan.c

@@ -278,6 +278,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
 			if (!ExecQual(node->bitmapqualorig, econtext, false))
 			{
 				/* Fails recheck, so drop it and loop back for another */
+				InstrCountFiltered2(node, 1);
 				ExecClearTuple(slot);
 				continue;
 			}

src/backend/executor/nodeBitmapIndexscan.c

@@ -22,7 +22,6 @@
 #include "postgres.h"
 
 #include "executor/execdebug.h"
-#include "executor/instrument.h"
 #include "executor/nodeBitmapIndexscan.h"
 #include "executor/nodeIndexscan.h"
 #include "miscadmin.h"

src/backend/executor/nodeBitmapOr.c

@@ -29,7 +29,6 @@
 #include "postgres.h"
 
 #include "executor/execdebug.h"
-#include "executor/instrument.h"
 #include "executor/nodeBitmapOr.h"
 #include "miscadmin.h"
 

src/backend/executor/nodeGroup.c

@@ -118,6 +118,8 @@ ExecGroup(GroupState *node)
 				return result;
 			}
 		}
+		else
+			InstrCountFiltered1(node, 1);
 	}
 
 	/*
@@ -179,6 +181,8 @@ ExecGroup(GroupState *node)
 				return result;
 			}
 		}
+		else
+			InstrCountFiltered1(node, 1);
 	}
 
 	/* NOTREACHED */

src/backend/executor/nodeHash.c

@@ -28,7 +28,6 @@
 #include "commands/tablespace.h"
 #include "executor/execdebug.h"
 #include "executor/hashjoin.h"
-#include "executor/instrument.h"
 #include "executor/nodeHash.h"
 #include "executor/nodeHashjoin.h"
 #include "miscadmin.h"

src/backend/executor/nodeHashjoin.c

@@ -325,7 +325,11 @@ ExecHashJoin(HashJoinState *node)
 							return result;
 						}
 					}
+					else
+						InstrCountFiltered2(node, 1);
 				}
+				else
+					InstrCountFiltered1(node, 1);
 				break;
 
 			case HJ_FILL_OUTER_TUPLE:
@@ -360,6 +364,8 @@ ExecHashJoin(HashJoinState *node)
 							return result;
 						}
 					}
+					else
+						InstrCountFiltered2(node, 1);
 				}
 				break;
 
@@ -397,6 +403,8 @@ ExecHashJoin(HashJoinState *node)
 						return result;
 					}
 				}
+				else
+					InstrCountFiltered2(node, 1);
 				break;
 
 			case HJ_NEED_NEW_BATCH:

src/backend/executor/nodeIndexscan.c

@@ -96,7 +96,11 @@ IndexNext(IndexScanState *node)
 			econtext->ecxt_scantuple = slot;
 			ResetExprContext(econtext);
 			if (!ExecQual(node->indexqualorig, econtext, false))
-				continue;		/* nope, so ask index for another one */
+			{
+				/* Fails recheck, so drop it and loop back for another */
+				InstrCountFiltered2(node, 1);
+				continue;
+			}
 		}
 
 		return slot;

src/backend/executor/nodeMergejoin.c

@@ -505,6 +505,8 @@ MJFillOuter(MergeJoinState *node)
 			return result;
 		}
 	}
+	else
+		InstrCountFiltered2(node, 1);
 
 	return NULL;
 }
@@ -544,6 +546,8 @@ MJFillInner(MergeJoinState *node)
 			return result;
 		}
 	}
+	else
+		InstrCountFiltered2(node, 1);
 
 	return NULL;
 }
@@ -893,7 +897,11 @@ ExecMergeJoin(MergeJoinState *node)
 							return result;
 						}
 					}
+					else
+						InstrCountFiltered2(node, 1);
 				}
+				else
+					InstrCountFiltered1(node, 1);
 				break;
 
 				/*

src/backend/executor/nodeNestloop.c

@@ -214,6 +214,8 @@ ExecNestLoop(NestLoopState *node)
 						return result;
 					}
 				}
+				else
+					InstrCountFiltered2(node, 1);
 			}
 
 			/*
@@ -270,7 +272,11 @@ ExecNestLoop(NestLoopState *node)
 					return result;
 				}
 			}
+			else
+				InstrCountFiltered2(node, 1);
 		}
+		else
+			InstrCountFiltered1(node, 1);
 
 		/*
 		 * Tuple fails qual, so free per-tuple memory and try again.

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;
 

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