Do execGrouping.c via expression eval machinery, take two.

This has a performance benefit on own, although not hugely so. The
primary benefit is that it will allow for to JIT tuple deforming and
comparator invocations.

Large parts of this were previously committed (773aec7aa), but the
commit contained an omission around cross-type comparisons and was
thus reverted.

Author: Andres Freund
Discussion: https://postgr.es/m/20171129080934.amqqkke2zjtekd4t@alap3.anarazel.de

1 files changed, 53 insertions, 196 deletions

diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c
index 8e8dbb1f205..c4d0e040587 100644
--- a/src/backend/executor/execGrouping.c
+++ b/src/backend/executor/execGrouping.c
@@ -52,172 +52,33 @@ static int	TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tup
  *****************************************************************************/
 
 /*
- * execTuplesMatch
- *		Return true if two tuples match in all the indicated fields.
- *
- * This actually implements SQL's notion of "not distinct".  Two nulls
- * match, a null and a not-null don't match.
- *
- * slot1, slot2: the tuples to compare (must have same columns!)
- * numCols: the number of attributes to be examined
- * matchColIdx: array of attribute column numbers
- * eqFunctions: array of fmgr lookup info for the equality functions to use
- * evalContext: short-term memory context for executing the functions
- *
- * NB: evalContext is reset each time!
- */
-bool
-execTuplesMatch(TupleTableSlot *slot1,
-				TupleTableSlot *slot2,
-				int numCols,
-				AttrNumber *matchColIdx,
-				FmgrInfo *eqfunctions,
-				MemoryContext evalContext)
-{
-	MemoryContext oldContext;
-	bool		result;
-	int			i;
-
-	/* Reset and switch into the temp context. */
-	MemoryContextReset(evalContext);
-	oldContext = MemoryContextSwitchTo(evalContext);
-
-	/*
-	 * We cannot report a match without checking all the fields, but we can
-	 * report a non-match as soon as we find unequal fields.  So, start
-	 * comparing at the last field (least significant sort key). That's the
-	 * most likely to be different if we are dealing with sorted input.
-	 */
-	result = true;
-
-	for (i = numCols; --i >= 0;)
-	{
-		AttrNumber	att = matchColIdx[i];
-		Datum		attr1,
-					attr2;
-		bool		isNull1,
-					isNull2;
-
-		attr1 = slot_getattr(slot1, att, &isNull1);
-
-		attr2 = slot_getattr(slot2, att, &isNull2);
-
-		if (isNull1 != isNull2)
-		{
-			result = false;		/* one null and one not; they aren't equal */
-			break;
-		}
-
-		if (isNull1)
-			continue;			/* both are null, treat as equal */
-
-		/* Apply the type-specific equality function */
-
-		if (!DatumGetBool(FunctionCall2(&eqfunctions[i],
-										attr1, attr2)))
-		{
-			result = false;		/* they aren't equal */
-			break;
-		}
-	}
-
-	MemoryContextSwitchTo(oldContext);
-
-	return result;
-}
-
-/*
- * execTuplesUnequal
- *		Return true if two tuples are definitely unequal in the indicated
- *		fields.
- *
- * Nulls are neither equal nor unequal to anything else.  A true result
- * is obtained only if there are non-null fields that compare not-equal.
- *
- * Parameters are identical to execTuplesMatch.
- */
-bool
-execTuplesUnequal(TupleTableSlot *slot1,
-				  TupleTableSlot *slot2,
-				  int numCols,
-				  AttrNumber *matchColIdx,
-				  FmgrInfo *eqfunctions,
-				  MemoryContext evalContext)
-{
-	MemoryContext oldContext;
-	bool		result;
-	int			i;
-
-	/* Reset and switch into the temp context. */
-	MemoryContextReset(evalContext);
-	oldContext = MemoryContextSwitchTo(evalContext);
-
-	/*
-	 * We cannot report a match without checking all the fields, but we can
-	 * report a non-match as soon as we find unequal fields.  So, start
-	 * comparing at the last field (least significant sort key). That's the
-	 * most likely to be different if we are dealing with sorted input.
-	 */
-	result = false;
-
-	for (i = numCols; --i >= 0;)
-	{
-		AttrNumber	att = matchColIdx[i];
-		Datum		attr1,
-					attr2;
-		bool		isNull1,
-					isNull2;
-
-		attr1 = slot_getattr(slot1, att, &isNull1);
-
-		if (isNull1)
-			continue;			/* can't prove anything here */
-
-		attr2 = slot_getattr(slot2, att, &isNull2);
-
-		if (isNull2)
-			continue;			/* can't prove anything here */
-
-		/* Apply the type-specific equality function */
-
-		if (!DatumGetBool(FunctionCall2(&eqfunctions[i],
-										attr1, attr2)))
-		{
-			result = true;		/* they are unequal */
-			break;
-		}
-	}
-
-	MemoryContextSwitchTo(oldContext);
-
-	return result;
-}
-
-
-/*
  * execTuplesMatchPrepare
- *		Look up the equality functions needed for execTuplesMatch or
- *		execTuplesUnequal, given an array of equality operator OIDs.
- *
- * The result is a palloc'd array.
+ *		Build expression that can be evaluated using ExecQual(), returning
+ *		whether an ExprContext's inner/outer tuples are NOT DISTINCT
  */
-FmgrInfo *
-execTuplesMatchPrepare(int numCols,
-					   Oid *eqOperators)
+ExprState *
+execTuplesMatchPrepare(TupleDesc desc,
+					   int numCols,
+					   AttrNumber *keyColIdx,
+					   Oid *eqOperators,
+					   PlanState *parent)
 {
-	FmgrInfo   *eqFunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
+	Oid		   *eqFunctions = (Oid *) palloc(numCols * sizeof(Oid));
 	int			i;
+	ExprState  *expr;
+
+	if (numCols == 0)
+		return NULL;
 
+	/* lookup equality functions */
 	for (i = 0; i < numCols; i++)
-	{
-		Oid			eq_opr = eqOperators[i];
-		Oid			eq_function;
+		eqFunctions[i] = get_opcode(eqOperators[i]);
 
-		eq_function = get_opcode(eq_opr);
-		fmgr_info(eq_function, &eqFunctions[i]);
-	}
+	/* build actual expression */
+	expr = ExecBuildGroupingEqual(desc, desc, numCols, keyColIdx, eqFunctions,
+								  parent);
 
-	return eqFunctions;
+	return expr;
 }
 
 /*
@@ -233,12 +94,12 @@ execTuplesMatchPrepare(int numCols,
 void
 execTuplesHashPrepare(int numCols,
 					  Oid *eqOperators,
-					  FmgrInfo **eqFunctions,
+					  Oid **eqFuncOids,
 					  FmgrInfo **hashFunctions)
 {
 	int			i;
 
-	*eqFunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
+	*eqFuncOids = (Oid *) palloc(numCols * sizeof(Oid));
 	*hashFunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
 
 	for (i = 0; i < numCols; i++)
@@ -255,7 +116,7 @@ execTuplesHashPrepare(int numCols,
 				 eq_opr);
 		/* We're not supporting cross-type cases here */
 		Assert(left_hash_function == right_hash_function);
-		fmgr_info(eq_function, &(*eqFunctions)[i]);
+		(*eqFuncOids)[i] = eq_function;
 		fmgr_info(right_hash_function, &(*hashFunctions)[i]);
 	}
 }
@@ -288,8 +149,10 @@ execTuplesHashPrepare(int numCols,
  * storage that will live as long as the hashtable does.
  */
 TupleHashTable
-BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
-					FmgrInfo *eqfunctions,
+BuildTupleHashTable(PlanState *parent,
+					TupleDesc inputDesc,
+					int numCols, AttrNumber *keyColIdx,
+					Oid *eqfuncoids,
 					FmgrInfo *hashfunctions,
 					long nbuckets, Size additionalsize,
 					MemoryContext tablecxt, MemoryContext tempcxt,
@@ -297,6 +160,7 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
 {
 	TupleHashTable hashtable;
 	Size		entrysize = sizeof(TupleHashEntryData) + additionalsize;
+	MemoryContext oldcontext;
 
 	Assert(nbuckets > 0);
 
@@ -309,14 +173,13 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
 	hashtable->numCols = numCols;
 	hashtable->keyColIdx = keyColIdx;
 	hashtable->tab_hash_funcs = hashfunctions;
-	hashtable->tab_eq_funcs = eqfunctions;
 	hashtable->tablecxt = tablecxt;
 	hashtable->tempcxt = tempcxt;
 	hashtable->entrysize = entrysize;
 	hashtable->tableslot = NULL;	/* will be made on first lookup */
 	hashtable->inputslot = NULL;
 	hashtable->in_hash_funcs = NULL;
-	hashtable->cur_eq_funcs = NULL;
+	hashtable->cur_eq_func = NULL;
 
 	/*
 	 * If parallelism is in use, even if the master backend is performing the
@@ -333,6 +196,24 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
 
 	hashtable->hashtab = tuplehash_create(tablecxt, nbuckets, hashtable);
 
+	oldcontext = MemoryContextSwitchTo(hashtable->tablecxt);
+
+	/*
+	 * We copy the input tuple descriptor just for safety --- we assume all
+	 * input tuples will have equivalent descriptors.
+	 */
+	hashtable->tableslot = MakeSingleTupleTableSlot(CreateTupleDescCopy(inputDesc));
+
+	/* build comparator for all columns */
+	hashtable->tab_eq_func = ExecBuildGroupingEqual(inputDesc, inputDesc,
+													numCols,
+													keyColIdx, eqfuncoids,
+													parent);
+
+	MemoryContextSwitchTo(oldcontext);
+
+	hashtable->exprcontext = CreateExprContext(parent->state);
+
 	return hashtable;
 }
 
@@ -357,29 +238,13 @@ LookupTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
 	bool		found;
 	MinimalTuple key;
 
-	/* If first time through, clone the input slot to make table slot */
-	if (hashtable->tableslot == NULL)
-	{
-		TupleDesc	tupdesc;
-
-		oldContext = MemoryContextSwitchTo(hashtable->tablecxt);
-
-		/*
-		 * We copy the input tuple descriptor just for safety --- we assume
-		 * all input tuples will have equivalent descriptors.
-		 */
-		tupdesc = CreateTupleDescCopy(slot->tts_tupleDescriptor);
-		hashtable->tableslot = MakeSingleTupleTableSlot(tupdesc);
-		MemoryContextSwitchTo(oldContext);
-	}
-
 	/* Need to run the hash functions in short-lived context */
 	oldContext = MemoryContextSwitchTo(hashtable->tempcxt);
 
 	/* set up data needed by hash and match functions */
 	hashtable->inputslot = slot;
 	hashtable->in_hash_funcs = hashtable->tab_hash_funcs;
-	hashtable->cur_eq_funcs = hashtable->tab_eq_funcs;
+	hashtable->cur_eq_func = hashtable->tab_eq_func;
 
 	key = NULL;					/* flag to reference inputslot */
 
@@ -424,7 +289,7 @@ LookupTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
  */
 TupleHashEntry
 FindTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
-				   FmgrInfo *eqfunctions,
+				   ExprState *eqcomp,
 				   FmgrInfo *hashfunctions)
 {
 	TupleHashEntry entry;
@@ -437,7 +302,7 @@ FindTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
 	/* Set up data needed by hash and match functions */
 	hashtable->inputslot = slot;
 	hashtable->in_hash_funcs = hashfunctions;
-	hashtable->cur_eq_funcs = eqfunctions;
+	hashtable->cur_eq_func = eqcomp;
 
 	/* Search the hash table */
 	key = NULL;					/* flag to reference inputslot */
@@ -524,9 +389,6 @@ TupleHashTableHash(struct tuplehash_hash *tb, const MinimalTuple tuple)
  * See whether two tuples (presumably of the same hash value) match
  *
  * As above, the passed pointers are pointers to TupleHashEntryData.
- *
- * Also, the caller must select an appropriate memory context for running
- * the compare functions.  (dynahash.c doesn't change CurrentMemoryContext.)
  */
 static int
 TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tuple1, const MinimalTuple tuple2)
@@ -534,6 +396,7 @@ TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tuple1, const
 	TupleTableSlot *slot1;
 	TupleTableSlot *slot2;
 	TupleHashTable hashtable = (TupleHashTable) tb->private_data;
+	ExprContext *econtext = hashtable->exprcontext;
 
 	/*
 	 * We assume that simplehash.h will only ever call us with the first
@@ -548,13 +411,7 @@ TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tuple1, const
 	slot2 = hashtable->inputslot;
 
 	/* For crosstype comparisons, the inputslot must be first */
-	if (execTuplesMatch(slot2,
-						slot1,
-						hashtable->numCols,
-						hashtable->keyColIdx,
-						hashtable->cur_eq_funcs,
-						hashtable->tempcxt))
-		return 0;
-	else
-		return 1;
+	econtext->ecxt_innertuple = slot2;
+	econtext->ecxt_outertuple = slot1;
+	return !ExecQualAndReset(hashtable->cur_eq_func, econtext);
 }