Change function call information to be variable length.

Before this change FunctionCallInfoData, the struct arguments etc for
V1 function calls are stored in, always had space for
FUNC_MAX_ARGS/100 arguments, storing datums and their nullness in two
arrays.  For nearly every function call 100 arguments is far more than
needed, therefore wasting memory. Arg and argnull being two separate
arrays also guarantees that to access a single argument, two
cachelines have to be touched.

Change the layout so there's a single variable-length array with pairs
of value / isnull. That drastically reduces memory consumption for
most function calls (on x86-64 a two argument function now uses
64bytes, previously 936 bytes), and makes it very likely that argument
value and its nullness are on the same cacheline.

Arguments are stored in a new NullableDatum struct, which, due to
padding, needs more memory per argument than before. But as usually
far fewer arguments are stored, and individual arguments are cheaper
to access, that's still a clear win.  It's likely that there's other
places where conversion to NullableDatum arrays would make sense,
e.g. TupleTableSlots, but that's for another commit.

Because the function call information is now variable-length
allocations have to take the number of arguments into account. For
heap allocations that can be done with SizeForFunctionCallInfoData(),
for on-stack allocations there's a new LOCAL_FCINFO(name, nargs) macro
that helps to allocate an appropriately sized and aligned variable.

Some places with stack allocation function call information don't know
the number of arguments at compile time, and currently variably sized
stack allocations aren't allowed in postgres. Therefore allow for
FUNC_MAX_ARGS space in these cases. They're not that common, so for
now that seems acceptable.

Because of the need to allocate FunctionCallInfo of the appropriate
size, older extensions may need to update their code. To avoid subtle
breakages, the FunctionCallInfoData struct has been renamed to
FunctionCallInfoBaseData. Most code only references FunctionCallInfo,
so that shouldn't cause much collateral damage.

This change is also a prerequisite for more efficient expression JIT
compilation (by allocating the function call information on the stack,
allowing LLVM to optimize it away); previously the size of the call
information caused problems inside LLVM's optimizer.

Author: Andres Freund
Reviewed-By: Tom Lane
Discussion: https://postgr.es/m/20180605172952.x34m5uz6ju6enaem@alap3.anarazel.de

1 files changed, 76 insertions, 63 deletions

diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 5a7206f5882..5c5f655645d 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -387,7 +387,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_ALTERNATIVE_SUBPLAN,
 		&&CASE_EEOP_AGG_STRICT_DESERIALIZE,
 		&&CASE_EEOP_AGG_DESERIALIZE,
-		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK,
+		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_ARGS,
+		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_NULLS,
 		&&CASE_EEOP_AGG_INIT_TRANS,
 		&&CASE_EEOP_AGG_STRICT_TRANS_CHECK,
 		&&CASE_EEOP_AGG_PLAIN_TRANS_BYVAL,
@@ -631,14 +632,14 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		EEO_CASE(EEOP_FUNCEXPR_STRICT)
 		{
 			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
-			bool	   *argnull = fcinfo->argnull;
+			NullableDatum *args = fcinfo->args;
 			int			argno;
 			Datum		d;
 
 			/* strict function, so check for NULL args */
 			for (argno = 0; argno < op->d.func.nargs; argno++)
 			{
-				if (argnull[argno])
+				if (args[argno].isnull)
 				{
 					*op->resnull = true;
 					goto strictfail;
@@ -1054,8 +1055,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 				FunctionCallInfo fcinfo_out;
 
 				fcinfo_out = op->d.iocoerce.fcinfo_data_out;
-				fcinfo_out->arg[0] = *op->resvalue;
-				fcinfo_out->argnull[0] = false;
+				fcinfo_out->args[0].value = *op->resvalue;
+				fcinfo_out->args[0].isnull = false;
 
 				fcinfo_out->isnull = false;
 				str = DatumGetCString(FunctionCallInvoke(fcinfo_out));
@@ -1071,8 +1072,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 				Datum		d;
 
 				fcinfo_in = op->d.iocoerce.fcinfo_data_in;
-				fcinfo_in->arg[0] = PointerGetDatum(str);
-				fcinfo_in->argnull[0] = *op->resnull;
+				fcinfo_in->args[0].value = PointerGetDatum(str);
+				fcinfo_in->args[0].isnull = *op->resnull;
 				/* second and third arguments are already set up */
 
 				fcinfo_in->isnull = false;
@@ -1099,23 +1100,23 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		{
 			/*
 			 * IS DISTINCT FROM must evaluate arguments (already done into
-			 * fcinfo->arg/argnull) to determine whether they are NULL; if
-			 * either is NULL then the result is determined.  If neither is
-			 * NULL, then proceed to evaluate the comparison function, which
-			 * is just the type's standard equality operator.  We need not
-			 * care whether that function is strict.  Because the handling of
-			 * nulls is different, we can't just reuse EEOP_FUNCEXPR.
+			 * fcinfo->args) to determine whether they are NULL; if either is
+			 * NULL then the result is determined.  If neither is NULL, then
+			 * proceed to evaluate the comparison function, which is just the
+			 * type's standard equality operator.  We need not care whether
+			 * that function is strict.  Because the handling of nulls is
+			 * different, we can't just reuse EEOP_FUNCEXPR.
 			 */
 			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
 
 			/* check function arguments for NULLness */
-			if (fcinfo->argnull[0] && fcinfo->argnull[1])
+			if (fcinfo->args[0].isnull && fcinfo->args[1].isnull)
 			{
 				/* Both NULL? Then is not distinct... */
 				*op->resvalue = BoolGetDatum(false);
 				*op->resnull = false;
 			}
-			else if (fcinfo->argnull[0] || fcinfo->argnull[1])
+			else if (fcinfo->args[0].isnull || fcinfo->args[1].isnull)
 			{
 				/* Only one is NULL? Then is distinct... */
 				*op->resvalue = BoolGetDatum(true);
@@ -1141,12 +1142,12 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		{
 			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
 
-			if (fcinfo->argnull[0] && fcinfo->argnull[1])
+			if (fcinfo->args[0].isnull && fcinfo->args[1].isnull)
 			{
 				*op->resvalue = BoolGetDatum(true);
 				*op->resnull = false;
 			}
-			else if (fcinfo->argnull[0] || fcinfo->argnull[1])
+			else if (fcinfo->args[0].isnull || fcinfo->args[1].isnull)
 			{
 				*op->resvalue = BoolGetDatum(false);
 				*op->resnull = false;
@@ -1167,12 +1168,12 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		EEO_CASE(EEOP_NULLIF)
 		{
 			/*
-			 * The arguments are already evaluated into fcinfo->arg/argnull.
+			 * The arguments are already evaluated into fcinfo->args.
 			 */
 			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
 
 			/* if either argument is NULL they can't be equal */
-			if (!fcinfo->argnull[0] && !fcinfo->argnull[1])
+			if (!fcinfo->args[0].isnull && !fcinfo->args[1].isnull)
 			{
 				Datum		result;
 
@@ -1190,8 +1191,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			}
 
 			/* Arguments aren't equal, so return the first one */
-			*op->resvalue = fcinfo->arg[0];
-			*op->resnull = fcinfo->argnull[0];
+			*op->resvalue = fcinfo->args[0].value;
+			*op->resnull = fcinfo->args[0].isnull;
 
 			EEO_NEXT();
 		}
@@ -1257,7 +1258,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 
 			/* force NULL result if strict fn and NULL input */
 			if (op->d.rowcompare_step.finfo->fn_strict &&
-				(fcinfo->argnull[0] || fcinfo->argnull[1]))
+				(fcinfo->args[0].isnull || fcinfo->args[1].isnull))
 			{
 				*op->resnull = true;
 				EEO_JUMP(op->d.rowcompare_step.jumpnull);
@@ -1496,10 +1497,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		/* evaluate a strict aggregate deserialization function */
 		EEO_CASE(EEOP_AGG_STRICT_DESERIALIZE)
 		{
-			bool	   *argnull = op->d.agg_deserialize.fcinfo_data->argnull;
-
 			/* Don't call a strict deserialization function with NULL input */
-			if (argnull[0])
+			if (op->d.agg_deserialize.fcinfo_data->args[0].isnull)
 				EEO_JUMP(op->d.agg_deserialize.jumpnull);
 
 			/* fallthrough */
@@ -1529,7 +1528,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		 * Check that a strict aggregate transition / combination function's
 		 * input is not NULL.
 		 */
-		EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK)
+		EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK_NULLS)
 		{
 			int			argno;
 			bool	   *nulls = op->d.agg_strict_input_check.nulls;
@@ -1543,6 +1542,20 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
+		EEO_CASE(EEOP_AGG_STRICT_INPUT_CHECK_ARGS)
+		{
+			int			argno;
+			NullableDatum *args = op->d.agg_strict_input_check.args;
+			int			nargs = op->d.agg_strict_input_check.nargs;
+
+			for (argno = 0; argno < nargs; argno++)
+			{
+				if (args[argno].isnull)
+					EEO_JUMP(op->d.agg_strict_input_check.jumpnull);
+			}
+			EEO_NEXT();
+		}
+
 		/*
 		 * Initialize an aggregate's first value if necessary.
 		 */
@@ -1613,7 +1626,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 
 			Assert(pertrans->transtypeByVal);
 
-			fcinfo = &pertrans->transfn_fcinfo;
+			fcinfo = pertrans->transfn_fcinfo;
 
 			/* cf. select_current_set() */
 			aggstate->curaggcontext = op->d.agg_trans.aggcontext;
@@ -1625,8 +1638,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			/* invoke transition function in per-tuple context */
 			oldContext = MemoryContextSwitchTo(aggstate->tmpcontext->ecxt_per_tuple_memory);
 
-			fcinfo->arg[0] = pergroup->transValue;
-			fcinfo->argnull[0] = pergroup->transValueIsNull;
+			fcinfo->args[0].value = pergroup->transValue;
+			fcinfo->args[0].isnull = pergroup->transValueIsNull;
 			fcinfo->isnull = false; /* just in case transfn doesn't set it */
 
 			newVal = FunctionCallInvoke(fcinfo);
@@ -1664,7 +1677,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 
 			Assert(!pertrans->transtypeByVal);
 
-			fcinfo = &pertrans->transfn_fcinfo;
+			fcinfo = pertrans->transfn_fcinfo;
 
 			/* cf. select_current_set() */
 			aggstate->curaggcontext = op->d.agg_trans.aggcontext;
@@ -1676,8 +1689,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			/* invoke transition function in per-tuple context */
 			oldContext = MemoryContextSwitchTo(aggstate->tmpcontext->ecxt_per_tuple_memory);
 
-			fcinfo->arg[0] = pergroup->transValue;
-			fcinfo->argnull[0] = pergroup->transValueIsNull;
+			fcinfo->args[0].value = pergroup->transValue;
+			fcinfo->args[0].isnull = pergroup->transValueIsNull;
 			fcinfo->isnull = false; /* just in case transfn doesn't set it */
 
 			newVal = FunctionCallInvoke(fcinfo);
@@ -2075,7 +2088,7 @@ ExecJustApplyFuncToCase(ExprState *state, ExprContext *econtext, bool *isnull)
 {
 	ExprEvalStep *op = &state->steps[0];
 	FunctionCallInfo fcinfo;
-	bool	   *argnull;
+	NullableDatum *args;
 	int			argno;
 	Datum		d;
 
@@ -2089,12 +2102,12 @@ ExecJustApplyFuncToCase(ExprState *state, ExprContext *econtext, bool *isnull)
 	op++;
 
 	fcinfo = op->d.func.fcinfo_data;
-	argnull = fcinfo->argnull;
+	args = fcinfo->args;
 
 	/* strict function, so check for NULL args */
 	for (argno = 0; argno < op->d.func.nargs; argno++)
 	{
-		if (argnull[argno])
+		if (args[argno].isnull)
 		{
 			*isnull = true;
 			return (Datum) 0;
@@ -2220,14 +2233,14 @@ ExecEvalFuncExprStrictFusage(ExprState *state, ExprEvalStep *op,
 
 	FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
 	PgStat_FunctionCallUsage fcusage;
-	bool	   *argnull = fcinfo->argnull;
+	NullableDatum *args = fcinfo->args;
 	int			argno;
 	Datum		d;
 
 	/* strict function, so check for NULL args */
 	for (argno = 0; argno < op->d.func.nargs; argno++)
 	{
-		if (argnull[argno])
+		if (args[argno].isnull)
 		{
 			*op->resnull = true;
 			return;
@@ -2317,8 +2330,8 @@ ExecEvalParamExtern(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
 void
 ExecEvalSQLValueFunction(ExprState *state, ExprEvalStep *op)
 {
+	LOCAL_FCINFO(fcinfo, 0);
 	SQLValueFunction *svf = op->d.sqlvaluefunction.svf;
-	FunctionCallInfoData fcinfo;
 
 	*op->resnull = false;
 
@@ -2350,24 +2363,24 @@ ExecEvalSQLValueFunction(ExprState *state, ExprEvalStep *op)
 		case SVFOP_CURRENT_ROLE:
 		case SVFOP_CURRENT_USER:
 		case SVFOP_USER:
-			InitFunctionCallInfoData(fcinfo, NULL, 0, InvalidOid, NULL, NULL);
-			*op->resvalue = current_user(&fcinfo);
-			*op->resnull = fcinfo.isnull;
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = current_user(fcinfo);
+			*op->resnull = fcinfo->isnull;
 			break;
 		case SVFOP_SESSION_USER:
-			InitFunctionCallInfoData(fcinfo, NULL, 0, InvalidOid, NULL, NULL);
-			*op->resvalue = session_user(&fcinfo);
-			*op->resnull = fcinfo.isnull;
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = session_user(fcinfo);
+			*op->resnull = fcinfo->isnull;
 			break;
 		case SVFOP_CURRENT_CATALOG:
-			InitFunctionCallInfoData(fcinfo, NULL, 0, InvalidOid, NULL, NULL);
-			*op->resvalue = current_database(&fcinfo);
-			*op->resnull = fcinfo.isnull;
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = current_database(fcinfo);
+			*op->resnull = fcinfo->isnull;
 			break;
 		case SVFOP_CURRENT_SCHEMA:
-			InitFunctionCallInfoData(fcinfo, NULL, 0, InvalidOid, NULL, NULL);
-			*op->resvalue = current_schema(&fcinfo);
-			*op->resnull = fcinfo.isnull;
+			InitFunctionCallInfoData(*fcinfo, NULL, 0, InvalidOid, NULL, NULL);
+			*op->resvalue = current_schema(fcinfo);
+			*op->resnull = fcinfo->isnull;
 			break;
 	}
 }
@@ -2800,8 +2813,8 @@ ExecEvalMinMax(ExprState *state, ExprEvalStep *op)
 	int			off;
 
 	/* set at initialization */
-	Assert(fcinfo->argnull[0] == false);
-	Assert(fcinfo->argnull[1] == false);
+	Assert(fcinfo->args[0].isnull == false);
+	Assert(fcinfo->args[1].isnull == false);
 
 	/* default to null result */
 	*op->resnull = true;
@@ -2823,8 +2836,8 @@ ExecEvalMinMax(ExprState *state, ExprEvalStep *op)
 			int			cmpresult;
 
 			/* apply comparison function */
-			fcinfo->arg[0] = *op->resvalue;
-			fcinfo->arg[1] = values[off];
+			fcinfo->args[0].value = *op->resvalue;
+			fcinfo->args[1].value = values[off];
 
 			fcinfo->isnull = false;
 			cmpresult = DatumGetInt32(FunctionCallInvoke(fcinfo));
@@ -3324,7 +3337,7 @@ ExecEvalConvertRowtype(ExprState *state, ExprEvalStep *op, ExprContext *econtext
  * Evaluate "scalar op ANY/ALL (array)".
  *
  * Source array is in our result area, scalar arg is already evaluated into
- * fcinfo->arg[0]/argnull[0].
+ * fcinfo->args[0].
  *
  * The operator always yields boolean, and we combine the results across all
  * array elements using OR and AND (for ANY and ALL respectively).  Of course
@@ -3376,7 +3389,7 @@ ExecEvalScalarArrayOp(ExprState *state, ExprEvalStep *op)
 	 * If the scalar is NULL, and the function is strict, return NULL; no
 	 * point in iterating the loop.
 	 */
-	if (fcinfo->argnull[0] && strictfunc)
+	if (fcinfo->args[0].isnull && strictfunc)
 	{
 		*op->resnull = true;
 		return;
@@ -3416,20 +3429,20 @@ ExecEvalScalarArrayOp(ExprState *state, ExprEvalStep *op)
 		/* Get array element, checking for NULL */
 		if (bitmap && (*bitmap & bitmask) == 0)
 		{
-			fcinfo->arg[1] = (Datum) 0;
-			fcinfo->argnull[1] = true;
+			fcinfo->args[1].value = (Datum) 0;
+			fcinfo->args[1].isnull = true;
 		}
 		else
 		{
 			elt = fetch_att(s, typbyval, typlen);
 			s = att_addlength_pointer(s, typlen, s);
 			s = (char *) att_align_nominal(s, typalign);
-			fcinfo->arg[1] = elt;
-			fcinfo->argnull[1] = false;
+			fcinfo->args[1].value = elt;
+			fcinfo->args[1].isnull = false;
 		}
 
 		/* Call comparison function */
-		if (fcinfo->argnull[1] && strictfunc)
+		if (fcinfo->args[1].isnull && strictfunc)
 		{
 			fcinfo->isnull = true;
 			thisresult = (Datum) 0;
@@ -4044,7 +4057,7 @@ ExecEvalSysVar(ExprState *state, ExprEvalStep *op, ExprContext *econtext,
 void
 ExecAggInitGroup(AggState *aggstate, AggStatePerTrans pertrans, AggStatePerGroup pergroup)
 {
-	FunctionCallInfo fcinfo = &pertrans->transfn_fcinfo;
+	FunctionCallInfo fcinfo = pertrans->transfn_fcinfo;
 	MemoryContext oldContext;
 
 	/*
@@ -4055,7 +4068,7 @@ ExecAggInitGroup(AggState *aggstate, AggStatePerTrans pertrans, AggStatePerGroup
 	 */
 	oldContext = MemoryContextSwitchTo(
 									   aggstate->curaggcontext->ecxt_per_tuple_memory);
-	pergroup->transValue = datumCopy(fcinfo->arg[1],
+	pergroup->transValue = datumCopy(fcinfo->args[1].value,
 									 pertrans->transtypeByVal,
 									 pertrans->transtypeLen);
 	pergroup->transValueIsNull = false;