Do execGrouping.c via expression eval machinery.

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.

Author: Andres Freund
Discussion: https://postgr.es/m/[email protected]

Author: anarazel

src/backend/executor/execExpr.c

@@ -3193,3 +3193,121 @@ ExecBuildAggTransCall(ExprState *state, AggState *aggstate,
 		as->d.agg_strict_trans_check.jumpnull = state->steps_len;
 	}
 }
+
+/*
+ * Build equality expression that can be evaluated using ExecQual(), returning
+ * true if the expression context's inner/outer tuple are NOT DISTINCT. I.e
+ * two nulls match, a null and a not-null don't match.
+ *
+ * desc: tuple descriptor of the to-be-compared tuples
+ * numCols: the number of attributes to be examined
+ * keyColIdx: array of attribute column numbers
+ * eqFunctions: array of function oids of the equality functions to use
+ * parent: parent executor node
+ */
+ExprState *
+ExecBuildGroupingEqual(TupleDesc desc,
+					   int numCols,
+					   AttrNumber *keyColIdx,
+					   Oid *eqfunctions,
+					   PlanState *parent)
+{
+	ExprState  *state = makeNode(ExprState);
+	ExprEvalStep scratch = {0};
+	int			natt;
+	int			maxatt = -1;
+	List	   *adjust_jumps = NIL;
+	ListCell   *lc;
+
+	/*
+	 * When no columns are actually compared, the result's always true. See
+	 * special case in ExecQual().
+	 */
+	if (numCols == 0)
+		return NULL;
+
+	state->expr = NULL;
+	state->flags = EEO_FLAG_IS_QUAL;
+	state->parent = parent;
+
+	scratch.resvalue = &state->resvalue;
+	scratch.resnull = &state->resnull;
+
+	/* compute max needed attribute */
+	for (natt = 0; natt < numCols; natt++)
+	{
+		int			attno = keyColIdx[natt];
+
+		if (attno > maxatt)
+			maxatt = attno;
+	}
+	Assert(maxatt >= 0);
+
+	/* push deform steps */
+	scratch.opcode = EEOP_INNER_FETCHSOME;
+	scratch.d.fetch.last_var = maxatt;
+	ExprEvalPushStep(state, &scratch);
+
+	scratch.opcode = EEOP_OUTER_FETCHSOME;
+	scratch.d.fetch.last_var = maxatt;
+	ExprEvalPushStep(state, &scratch);
+
+	/*
+	 * 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.
+	 */
+	for (natt = numCols; --natt >= 0;)
+	{
+		int			attno = keyColIdx[natt];
+		Form_pg_attribute att = TupleDescAttr(desc, attno - 1);
+		Var		   *larg,
+				   *rarg;
+		List	   *args;
+
+		/*
+		 * Reusing ExecInitFunc() requires creating Vars, but still seems
+		 * worth it from a code reuse perspective.
+		 */
+
+		/* left arg */
+		larg = makeVar(INNER_VAR, attno, att->atttypid,
+					   att->atttypmod, InvalidOid, 0);
+		/* right arg */
+		rarg = makeVar(OUTER_VAR, attno, att->atttypid,
+					   att->atttypmod, InvalidOid, 0);
+		args = list_make2(larg, rarg);
+
+		/* evaluate distinctness */
+		ExecInitFunc(&scratch, NULL,
+					 args, eqfunctions[natt], InvalidOid,
+					 state);
+		scratch.opcode = EEOP_NOT_DISTINCT;
+		ExprEvalPushStep(state, &scratch);
+
+		/* then emit EEOP_QUAL to detect if result is false (or null) */
+		scratch.opcode = EEOP_QUAL;
+		scratch.d.qualexpr.jumpdone = -1;
+		ExprEvalPushStep(state, &scratch);
+		adjust_jumps = lappend_int(adjust_jumps,
+								   state->steps_len - 1);
+	}
+
+	/* adjust jump targets */
+	foreach(lc, adjust_jumps)
+	{
+		ExprEvalStep *as = &state->steps[lfirst_int(lc)];
+
+		Assert(as->opcode == EEOP_QUAL);
+		Assert(as->d.qualexpr.jumpdone == -1);
+		as->d.qualexpr.jumpdone = state->steps_len;
+	}
+
+	scratch.resvalue = NULL;
+	scratch.resnull = NULL;
+	scratch.opcode = EEOP_DONE;
+	ExprEvalPushStep(state, &scratch);
+
+	ExecReadyExpr(state);
+
+	return state;
+}

src/backend/executor/execExprInterp.c

@@ -355,6 +355,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_MAKE_READONLY,
 		&&CASE_EEOP_IOCOERCE,
 		&&CASE_EEOP_DISTINCT,
+		&&CASE_EEOP_NOT_DISTINCT,
 		&&CASE_EEOP_NULLIF,
 		&&CASE_EEOP_SQLVALUEFUNCTION,
 		&&CASE_EEOP_CURRENTOFEXPR,
@@ -1198,6 +1199,34 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
+		/* see EEOP_DISTINCT for comments, this is just inverted */
+		EEO_CASE(EEOP_NOT_DISTINCT)
+		{
+			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
+
+			if (fcinfo->argnull[0] && fcinfo->argnull[1])
+			{
+				*op->resvalue = BoolGetDatum(true);
+				*op->resnull = false;
+			}
+			else if (fcinfo->argnull[0] || fcinfo->argnull[1])
+			{
+				*op->resvalue = BoolGetDatum(false);
+				*op->resnull = false;
+			}
+			else
+			{
+				Datum		eqresult;
+
+				fcinfo->isnull = false;
+				eqresult = op->d.func.fn_addr(fcinfo);
+				*op->resvalue = eqresult;
+				*op->resnull = fcinfo->isnull;
+			}
+
+			EEO_NEXT();
+		}
+
 		EEO_CASE(EEOP_NULLIF)
 		{
 			/*