Add special case fast-paths for strict functions

Many STRICT function calls will have one or two arguments, in which
case we can speed up checking for NULL input by avoiding setting up
a loop over the arguments. This adds EEOP_FUNCEXPR_STRICT_1 and the
corresponding EEOP_FUNCEXPR_STRICT_2 for functions with one and two
arguments respectively.

Author: Andres Freund <andres@anarazel.de>
Co-authored-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Discussion: https://postgr.es/m/415721CE-7D2E-4B74-B5D9-1950083BA03E@yesql.se
Discussion: https://postgr.es/m/20191023163849.sosqbfs5yenocez3@alap3.anarazel.de

2 files changed, 85 insertions, 2 deletions

diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index 0175b152980..f1569879b52 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -2788,7 +2788,15 @@ ExecInitFunc(ExprEvalStep *scratch, Expr *node, List *args, Oid funcid,
 	if (pgstat_track_functions <= flinfo->fn_stats)
 	{
 		if (flinfo->fn_strict && nargs > 0)
-			scratch->opcode = EEOP_FUNCEXPR_STRICT;
+		{
+			/* Choose nargs optimized implementation if available. */
+			if (nargs == 1)
+				scratch->opcode = EEOP_FUNCEXPR_STRICT_1;
+			else if (nargs == 2)
+				scratch->opcode = EEOP_FUNCEXPR_STRICT_2;
+			else
+				scratch->opcode = EEOP_FUNCEXPR_STRICT;
+		}
 		else
 			scratch->opcode = EEOP_FUNCEXPR;
 	}
@@ -3892,6 +3900,8 @@ ExecBuildAggTrans(AggState *aggstate, AggStatePerPhase phase,
 		{
 			if (strictnulls)
 				scratch.opcode = EEOP_AGG_STRICT_INPUT_CHECK_NULLS;
+			else if (strictargs && pertrans->numTransInputs == 1)
+				scratch.opcode = EEOP_AGG_STRICT_INPUT_CHECK_ARGS_1;
 			else
 				scratch.opcode = EEOP_AGG_STRICT_INPUT_CHECK_ARGS;
 			scratch.d.agg_strict_input_check.nulls = strictnulls;
@@ -3968,6 +3978,7 @@ ExecBuildAggTrans(AggState *aggstate, AggStatePerPhase phase,
 				as->d.jump.jumpdone = state->steps_len;
 			}
 			else if (as->opcode == EEOP_AGG_STRICT_INPUT_CHECK_ARGS ||
+					 as->opcode == EEOP_AGG_STRICT_INPUT_CHECK_ARGS_1 ||
 					 as->opcode == EEOP_AGG_STRICT_INPUT_CHECK_NULLS)
 			{
 				Assert(as->d.agg_strict_input_check.jumpnull == -1);
diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 491ecad8dc6..8a72b5e70a4 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -366,7 +366,9 @@ ExecReadyInterpretedExpr(ExprState *state)
 			return;
 		}
 		else if (step0 == EEOP_CASE_TESTVAL &&
-				 step1 == EEOP_FUNCEXPR_STRICT)
+				 (step1 == EEOP_FUNCEXPR_STRICT ||
+				  step1 == EEOP_FUNCEXPR_STRICT_1 ||
+				  step1 == EEOP_FUNCEXPR_STRICT_2))
 		{
 			state->evalfunc_private = ExecJustApplyFuncToCase;
 			return;
@@ -498,6 +500,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_CONST,
 		&&CASE_EEOP_FUNCEXPR,
 		&&CASE_EEOP_FUNCEXPR_STRICT,
+		&&CASE_EEOP_FUNCEXPR_STRICT_1,
+		&&CASE_EEOP_FUNCEXPR_STRICT_2,
 		&&CASE_EEOP_FUNCEXPR_FUSAGE,
 		&&CASE_EEOP_FUNCEXPR_STRICT_FUSAGE,
 		&&CASE_EEOP_BOOL_AND_STEP_FIRST,
@@ -575,6 +579,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_AGG_STRICT_DESERIALIZE,
 		&&CASE_EEOP_AGG_DESERIALIZE,
 		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_ARGS,
+		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_ARGS_1,
 		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_NULLS,
 		&&CASE_EEOP_AGG_PLAIN_PERGROUP_NULLCHECK,
 		&&CASE_EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL,
@@ -925,6 +930,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
+		/* strict function call with more than two arguments */
 		EEO_CASE(EEOP_FUNCEXPR_STRICT)
 		{
 			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
@@ -932,6 +938,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			int			nargs = op->d.func.nargs;
 			Datum		d;
 
+			Assert(nargs > 2);
+
 			/* strict function, so check for NULL args */
 			for (int argno = 0; argno < nargs; argno++)
 			{
@@ -950,6 +958,54 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
+		/* strict function call with one argument */
+		EEO_CASE(EEOP_FUNCEXPR_STRICT_1)
+		{
+			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
+			NullableDatum *args = fcinfo->args;
+
+			Assert(op->d.func.nargs == 1);
+
+			/* strict function, so check for NULL args */
+			if (args[0].isnull)
+				*op->resnull = true;
+			else
+			{
+				Datum		d;
+
+				fcinfo->isnull = false;
+				d = op->d.func.fn_addr(fcinfo);
+				*op->resvalue = d;
+				*op->resnull = fcinfo->isnull;
+			}
+
+			EEO_NEXT();
+		}
+
+		/* strict function call with two arguments */
+		EEO_CASE(EEOP_FUNCEXPR_STRICT_2)
+		{
+			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
+			NullableDatum *args = fcinfo->args;
+
+			Assert(op->d.func.nargs == 2);
+
+			/* strict function, so check for NULL args */
+			if (args[0].isnull || args[1].isnull)
+				*op->resnull = true;
+			else
+			{
+				Datum		d;
+
+				fcinfo->isnull = false;
+				d = op->d.func.fn_addr(fcinfo);
+				*op->resvalue = d;
+				*op->resnull = fcinfo->isnull;
+			}
+
+			EEO_NEXT();
+		}
+
 		EEO_CASE(EEOP_FUNCEXPR_FUSAGE)
 		{
 			/* not common enough to inline */
@@ -1982,11 +2038,14 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		 * input is not NULL.
 		 */
 
+		/* when checking more than one argument */
 		EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK_ARGS)
 		{
 			NullableDatum *args = op->d.agg_strict_input_check.args;
 			int			nargs = op->d.agg_strict_input_check.nargs;
 
+			Assert(nargs > 1);
+
 			for (int argno = 0; argno < nargs; argno++)
 			{
 				if (args[argno].isnull)
@@ -1995,6 +2054,19 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
+		/* special case for just one argument */
+		EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK_ARGS_1)
+		{
+			NullableDatum *args = op->d.agg_strict_input_check.args;
+			PG_USED_FOR_ASSERTS_ONLY int nargs = op->d.agg_strict_input_check.nargs;
+
+			Assert(nargs == 1);
+
+			if (args[0].isnull)
+				EEO_JUMP(op->d.agg_strict_input_check.jumpnull);
+			EEO_NEXT();
+		}
+
 		EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK_NULLS)
 		{
 			bool	   *nulls = op->d.agg_strict_input_check.nulls;