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, 143 insertions, 0 deletions

diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index c6eb3ebacf8..463e185a9a9 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -3193,3 +3193,146 @@ 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 ldesc, TupleDesc rdesc,
+					   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 latt = TupleDescAttr(ldesc, attno - 1);
+		Form_pg_attribute ratt = TupleDescAttr(rdesc, attno - 1);
+		Oid			foid = eqfunctions[natt];
+		FmgrInfo   *finfo;
+		FunctionCallInfo fcinfo;
+		AclResult	aclresult;
+
+		/* Check permission to call function */
+		aclresult = pg_proc_aclcheck(foid, GetUserId(), ACL_EXECUTE);
+		if (aclresult != ACLCHECK_OK)
+			aclcheck_error(aclresult, OBJECT_FUNCTION, get_func_name(foid));
+
+		InvokeFunctionExecuteHook(foid);
+
+		/* Set up the primary fmgr lookup information */
+		finfo = palloc0(sizeof(FmgrInfo));
+		fcinfo = palloc0(sizeof(FunctionCallInfoData));
+		fmgr_info(foid, finfo);
+		fmgr_info_set_expr(NULL, finfo);
+		InitFunctionCallInfoData(*fcinfo, finfo, 2,
+								 InvalidOid, NULL, NULL);
+
+		/* left arg */
+		scratch.opcode = EEOP_INNER_VAR;
+		scratch.d.var.attnum = attno - 1;
+		scratch.d.var.vartype = latt->atttypid;
+		scratch.resvalue = &fcinfo->arg[0];
+		scratch.resnull = &fcinfo->argnull[0];
+		ExprEvalPushStep(state, &scratch);
+
+		/* right arg */
+		scratch.opcode = EEOP_OUTER_VAR;
+		scratch.d.var.attnum = attno - 1;
+		scratch.d.var.vartype = ratt->atttypid;
+		scratch.resvalue = &fcinfo->arg[1];
+		scratch.resnull = &fcinfo->argnull[1];
+		ExprEvalPushStep(state, &scratch);
+
+		/* evaluate distinctness */
+		scratch.opcode = EEOP_NOT_DISTINCT;
+		scratch.d.func.finfo = finfo;
+		scratch.d.func.fcinfo_data = fcinfo;
+		scratch.d.func.fn_addr = finfo->fn_addr;
+		scratch.d.func.nargs = 2;
+		scratch.resvalue = &state->resvalue;
+		scratch.resnull = &state->resnull;
+		ExprEvalPushStep(state, &scratch);
+
+		/* then emit EEOP_QUAL to detect if result is false (or null) */
+		scratch.opcode = EEOP_QUAL;
+		scratch.d.qualexpr.jumpdone = -1;
+		scratch.resvalue = &state->resvalue;
+		scratch.resnull = &state->resnull;
+		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;
+}