Cache argument type information in json(b) aggregate functions.

These functions have been looking up type info for every row they
process. Instead of doing that we only look them up the first time
through and stash the information in the aggregate state object.

Affects json_agg, json_object_agg, jsonb_agg and jsonb_object_agg.

There is plenty more work to do in making these more efficient,
especially the jsonb functions, but this is a virtually cost free
improvement that can be done right away.

Backpatch to 9.5 where the jsonb variants were introduced.

src/backend/utils/adt/json.c

@@ -68,6 +68,15 @@ typedef enum					/* type categories for datum_to_json */
 	JSONTYPE_OTHER				/* all else */
 } JsonTypeCategory;
 
+typedef struct JsonAggState
+{
+	StringInfo         str;
+	JsonTypeCategory   key_category;
+	Oid                key_output_func;
+	JsonTypeCategory   val_category;
+	Oid                val_output_func;
+} JsonAggState;
+
 static inline void json_lex(JsonLexContext *lex);
 static inline void json_lex_string(JsonLexContext *lex);
 static inline void json_lex_number(JsonLexContext *lex, char *s, bool *num_err);
@@ -1858,18 +1867,10 @@ to_json(PG_FUNCTION_ARGS)
 Datum
 json_agg_transfn(PG_FUNCTION_ARGS)
 {
-	Oid			val_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
 	MemoryContext aggcontext,
 				oldcontext;
-	StringInfo	state;
+	JsonAggState	*state;
 	Datum		val;
-	JsonTypeCategory tcategory;
-	Oid			outfuncoid;
-
-	if (val_type == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("could not determine input data type")));
 
 	if (!AggCheckCallContext(fcinfo, &aggcontext))
 	{
@@ -1879,50 +1880,59 @@ json_agg_transfn(PG_FUNCTION_ARGS)
 
 	if (PG_ARGISNULL(0))
 	{
+		Oid         arg_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
+
+		if (arg_type == InvalidOid)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("could not determine input data type")));
+
 		/*
-		 * Make this StringInfo in a context where it will persist for the
+		 * Make this state object in a context where it will persist for the
 		 * duration of the aggregate call.  MemoryContextSwitchTo is only
 		 * needed the first time, as the StringInfo routines make sure they
 		 * use the right context to enlarge the object if necessary.
 		 */
 		oldcontext = MemoryContextSwitchTo(aggcontext);
-		state = makeStringInfo();
+		state = (JsonAggState *) palloc(sizeof(JsonAggState));
+		state->str = makeStringInfo();
 		MemoryContextSwitchTo(oldcontext);
 
-		appendStringInfoChar(state, '[');
+		appendStringInfoChar(state->str, '[');
+		json_categorize_type(arg_type,&state->val_category,
+							 &state->val_output_func);
 	}
 	else
 	{
-		state = (StringInfo) PG_GETARG_POINTER(0);
-		appendStringInfoString(state, ", ");
+		state = (JsonAggState *) PG_GETARG_POINTER(0);
+		appendStringInfoString(state->str, ", ");
 	}
 
 	/* fast path for NULLs */
 	if (PG_ARGISNULL(1))
 	{
-		datum_to_json((Datum) 0, true, state, JSONTYPE_NULL, InvalidOid, false);
+		datum_to_json((Datum) 0, true, state->str, JSONTYPE_NULL,
+					  InvalidOid, false);
 		PG_RETURN_POINTER(state);
 	}
 
 	val = PG_GETARG_DATUM(1);
 
-	/* XXX we do this every time?? */
-	json_categorize_type(val_type,
-						 &tcategory, &outfuncoid);
-
 	/* add some whitespace if structured type and not first item */
 	if (!PG_ARGISNULL(0) &&
-		(tcategory == JSONTYPE_ARRAY || tcategory == JSONTYPE_COMPOSITE))
+		(state->val_category == JSONTYPE_ARRAY ||
+		 state->val_category == JSONTYPE_COMPOSITE))
 	{
-		appendStringInfoString(state, "\n ");
+		appendStringInfoString(state->str, "\n ");
 	}
 
-	datum_to_json(val, false, state, tcategory, outfuncoid, false);
+	datum_to_json(val, false, state->str, state->val_category,
+				  state->val_output_func, false);
 
 	/*
 	 * The transition type for array_agg() is declared to be "internal", which
 	 * is a pass-by-value type the same size as a pointer.  So we can safely
-	 * pass the ArrayBuildState pointer through nodeAgg.c's machinations.
+	 * pass the JsonAggState pointer through nodeAgg.c's machinations.
 	 */
 	PG_RETURN_POINTER(state);
 }
@@ -1933,19 +1943,21 @@ json_agg_transfn(PG_FUNCTION_ARGS)
 Datum
 json_agg_finalfn(PG_FUNCTION_ARGS)
 {
-	StringInfo	state;
+	JsonAggState	*state;
 
 	/* cannot be called directly because of internal-type argument */
 	Assert(AggCheckCallContext(fcinfo, NULL));
 
-	state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
+	state = PG_ARGISNULL(0) ?
+		NULL :
+		(JsonAggState *) PG_GETARG_POINTER(0);
 
 	/* NULL result for no rows in, as is standard with aggregates */
 	if (state == NULL)
 		PG_RETURN_NULL();
 
 	/* Else return state with appropriate array terminator added */
-	PG_RETURN_TEXT_P(catenate_stringinfo_string(state, "]"));
+	PG_RETURN_TEXT_P(catenate_stringinfo_string(state->str, "]"));
 }
 
 /*
@@ -1956,10 +1968,9 @@ json_agg_finalfn(PG_FUNCTION_ARGS)
 Datum
 json_object_agg_transfn(PG_FUNCTION_ARGS)
 {
-	Oid			val_type;
 	MemoryContext aggcontext,
 				oldcontext;
-	StringInfo	state;
+	JsonAggState	*state;
 	Datum		arg;
 
 	if (!AggCheckCallContext(fcinfo, &aggcontext))
@@ -1970,6 +1981,8 @@ json_object_agg_transfn(PG_FUNCTION_ARGS)
 
 	if (PG_ARGISNULL(0))
 	{
+		Oid			arg_type;
+
 		/*
 		 * Make the StringInfo in a context where it will persist for the
 		 * duration of the aggregate call. Switching context is only needed
@@ -1977,15 +1990,36 @@ json_object_agg_transfn(PG_FUNCTION_ARGS)
 		 * use the right context to enlarge the object if necessary.
 		 */
 		oldcontext = MemoryContextSwitchTo(aggcontext);
-		state = makeStringInfo();
+		state = (JsonAggState *) palloc(sizeof(JsonAggState));
+		state->str = makeStringInfo();
 		MemoryContextSwitchTo(oldcontext);
 
-		appendStringInfoString(state, "{ ");
+		arg_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
+
+		if (arg_type == InvalidOid)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("could not determine data type for argument 1")));
+
+		json_categorize_type(arg_type,&state->key_category,
+							 &state->key_output_func);
+
+		arg_type = get_fn_expr_argtype(fcinfo->flinfo, 2);
+
+		if (arg_type == InvalidOid)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("could not determine data type for argument 2")));
+
+		json_categorize_type(arg_type,&state->val_category,
+							 &state->val_output_func);
+
+		appendStringInfoString(state->str, "{ ");
 	}
 	else
 	{
-		state = (StringInfo) PG_GETARG_POINTER(0);
-		appendStringInfoString(state, ", ");
+		state = (JsonAggState *) PG_GETARG_POINTER(0);
+		appendStringInfoString(state->str, ", ");
 	}
 
 	/*
@@ -1995,12 +2029,6 @@ json_object_agg_transfn(PG_FUNCTION_ARGS)
 	 * type UNKNOWN, which fortunately does not matter to us, since
 	 * unknownout() works fine.
 	 */
-	val_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
-
-	if (val_type == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("could not determine data type for argument %d", 1)));
 
 	if (PG_ARGISNULL(1))
 		ereport(ERROR,
@@ -2009,23 +2037,18 @@ json_object_agg_transfn(PG_FUNCTION_ARGS)
 
 	arg = PG_GETARG_DATUM(1);
 
-	add_json(arg, false, state, val_type, true);
-
-	appendStringInfoString(state, " : ");
+	datum_to_json(arg, false, state->str, state->key_category,
+				  state->key_output_func, true);
 
-	val_type = get_fn_expr_argtype(fcinfo->flinfo, 2);
-
-	if (val_type == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("could not determine data type for argument %d", 2)));
+	appendStringInfoString(state->str, " : ");
 
 	if (PG_ARGISNULL(2))
 		arg = (Datum) 0;
 	else
 		arg = PG_GETARG_DATUM(2);
 
-	add_json(arg, PG_ARGISNULL(2), state, val_type, false);
+	datum_to_json(arg, PG_ARGISNULL(2), state->str, state->val_category,
+				  state->val_output_func, false);
 
 	PG_RETURN_POINTER(state);
 }
@@ -2036,19 +2059,19 @@ json_object_agg_transfn(PG_FUNCTION_ARGS)
 Datum
 json_object_agg_finalfn(PG_FUNCTION_ARGS)
 {
-	StringInfo	state;
+	JsonAggState	*state;
 
 	/* cannot be called directly because of internal-type argument */
 	Assert(AggCheckCallContext(fcinfo, NULL));
 
-	state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
+	state = PG_ARGISNULL(0) ? NULL : (JsonAggState *) PG_GETARG_POINTER(0);
 
 	/* NULL result for no rows in, as is standard with aggregates */
 	if (state == NULL)
 		PG_RETURN_NULL();
 
 	/* Else return state with appropriate object terminator added */
-	PG_RETURN_TEXT_P(catenate_stringinfo_string(state, " }"));
+	PG_RETURN_TEXT_P(catenate_stringinfo_string(state->str, " }"));
 }
 
 /*

src/backend/utils/adt/jsonb.c

@@ -59,6 +59,15 @@ typedef enum					/* type categories for datum_to_jsonb */
 	JSONBTYPE_OTHER				/* all else */
 } JsonbTypeCategory;
 
+typedef struct JsonbAggState
+{
+   JsonbInState      *res;
+   JsonbTypeCategory  key_category;
+   Oid                key_output_func;
+   JsonbTypeCategory  val_category;
+   Oid                val_output_func;
+} JsonbAggState;
+
 static inline Datum jsonb_from_cstring(char *json, int len);
 static size_t checkStringLen(size_t len);
 static void jsonb_in_object_start(void *pstate);
@@ -1573,12 +1582,10 @@ clone_parse_state(JsonbParseState *state)
 Datum
 jsonb_agg_transfn(PG_FUNCTION_ARGS)
 {
-	Oid			val_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
 	MemoryContext oldcontext,
 				aggcontext;
+	JsonbAggState *state;
 	JsonbInState elem;
-	JsonbTypeCategory tcategory;
-	Oid			outfuncoid;
 	Datum		val;
 	JsonbInState *result;
 	bool		single_scalar = false;
@@ -1587,48 +1594,56 @@ jsonb_agg_transfn(PG_FUNCTION_ARGS)
 	JsonbValue	v;
 	JsonbIteratorToken type;
 
-	if (val_type == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("could not determine input data type")));
-
 	if (!AggCheckCallContext(fcinfo, &aggcontext))
 	{
 		/* cannot be called directly because of internal-type argument */
 		elog(ERROR, "jsonb_agg_transfn called in non-aggregate context");
 	}
 
-	/* turn the argument into jsonb in the normal function context */
-
-	val = PG_ARGISNULL(1) ? (Datum) 0 : PG_GETARG_DATUM(1);
-
-	jsonb_categorize_type(val_type,
-						  &tcategory, &outfuncoid);
-
-	memset(&elem, 0, sizeof(JsonbInState));
-
-	datum_to_jsonb(val, PG_ARGISNULL(1), &elem, tcategory, outfuncoid, false);
-
-	jbelem = JsonbValueToJsonb(elem.res);
-
-	/* switch to the aggregate context for accumulation operations */
-
-	oldcontext = MemoryContextSwitchTo(aggcontext);
-
 	/* set up the accumulator on the first go round */
 
 	if (PG_ARGISNULL(0))
 	{
+
+		Oid         arg_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
+
+		if (arg_type == InvalidOid)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("could not determine input data type")));
+
+		oldcontext = MemoryContextSwitchTo(aggcontext);
+		state = palloc(sizeof(JsonbAggState));
 		result = palloc0(sizeof(JsonbInState));
+		state->res = result;
 		result->res = pushJsonbValue(&result->parseState,
 									 WJB_BEGIN_ARRAY, NULL);
+		MemoryContextSwitchTo(oldcontext);
 
+		jsonb_categorize_type(arg_type, &state->val_category,
+							  &state->val_output_func);
 	}
 	else
 	{
-		result = (JsonbInState *) PG_GETARG_POINTER(0);
+		state = (JsonbAggState *) PG_GETARG_POINTER(0);
+		result = state->res;
 	}
 
+	/* turn the argument into jsonb in the normal function context */
+
+	val = PG_ARGISNULL(1) ? (Datum) 0 : PG_GETARG_DATUM(1);
+
+	memset(&elem, 0, sizeof(JsonbInState));
+
+	datum_to_jsonb(val, PG_ARGISNULL(1), &elem, state->val_category,
+				   state->val_output_func, false);
+
+	jbelem = JsonbValueToJsonb(elem.res);
+
+	/* switch to the aggregate context for accumulation operations */
+
+	oldcontext = MemoryContextSwitchTo(aggcontext);
+
 	it = JsonbIteratorInit(&jbelem->root);
 
 	while ((type = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
@@ -1669,7 +1684,6 @@ jsonb_agg_transfn(PG_FUNCTION_ARGS)
 					v.val.numeric =
 					DatumGetNumeric(DirectFunctionCall1(numeric_uplus,
 											NumericGetDatum(v.val.numeric)));
-
 				}
 				result->res = pushJsonbValue(&result->parseState,
 											 type, &v);
@@ -1681,13 +1695,13 @@ jsonb_agg_transfn(PG_FUNCTION_ARGS)
 
 	MemoryContextSwitchTo(oldcontext);
 
-	PG_RETURN_POINTER(result);
+	PG_RETURN_POINTER(state);
 }
 
 Datum
 jsonb_agg_finalfn(PG_FUNCTION_ARGS)
 {
-	JsonbInState *arg;
+	JsonbAggState *arg;
 	JsonbInState result;
 	Jsonb	   *out;
 
@@ -1697,7 +1711,7 @@ jsonb_agg_finalfn(PG_FUNCTION_ARGS)
 	if (PG_ARGISNULL(0))
 		PG_RETURN_NULL();		/* returns null iff no input values */
 
-	arg = (JsonbInState *) PG_GETARG_POINTER(0);
+	arg = (JsonbAggState *) PG_GETARG_POINTER(0);
 
 	/*
 	 * We need to do a shallow clone of the argument in case the final
@@ -1706,12 +1720,11 @@ jsonb_agg_finalfn(PG_FUNCTION_ARGS)
 	 * values, just add the final array end marker.
 	 */
 
-	result.parseState = clone_parse_state(arg->parseState);
+	result.parseState = clone_parse_state(arg->res->parseState);
 
 	result.res = pushJsonbValue(&result.parseState,
 								WJB_END_ARRAY, NULL);
 
-
 	out = JsonbValueToJsonb(result.res);
 
 	PG_RETURN_POINTER(out);
@@ -1723,12 +1736,10 @@ jsonb_agg_finalfn(PG_FUNCTION_ARGS)
 Datum
 jsonb_object_agg_transfn(PG_FUNCTION_ARGS)
 {
-	Oid			val_type;
 	MemoryContext oldcontext,
 				aggcontext;
 	JsonbInState elem;
-	JsonbTypeCategory tcategory;
-	Oid			outfuncoid;
+	JsonbAggState *state;
 	Datum		val;
 	JsonbInState *result;
 	bool		single_scalar;
@@ -1744,14 +1755,47 @@ jsonb_object_agg_transfn(PG_FUNCTION_ARGS)
 		elog(ERROR, "jsonb_object_agg_transfn called in non-aggregate context");
 	}
 
-	/* turn the argument into jsonb in the normal function context */
+	/* set up the accumulator on the first go round */
 
-	val_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
+	if (PG_ARGISNULL(0))
+	{
+		Oid         arg_type;
 
-	if (val_type == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("could not determine input data type")));
+		oldcontext = MemoryContextSwitchTo(aggcontext);
+		state = palloc(sizeof(JsonbAggState));
+		result = palloc0(sizeof(JsonbInState));
+		state->res = result;
+		result->res = pushJsonbValue(&result->parseState,
+									 WJB_BEGIN_OBJECT, NULL);
+		MemoryContextSwitchTo(oldcontext);
+
+		arg_type = get_fn_expr_argtype(fcinfo->flinfo, 1);
+
+		if (arg_type == InvalidOid)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("could not determine input data type")));
+
+		jsonb_categorize_type(arg_type, &state->key_category,
+							  &state->key_output_func);
+
+		arg_type = get_fn_expr_argtype(fcinfo->flinfo, 2);
+
+		if (arg_type == InvalidOid)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("could not determine input data type")));
+
+		jsonb_categorize_type(arg_type, &state->val_category,
+							  &state->val_output_func);
+	}
+	else
+	{
+		state = (JsonbAggState *) PG_GETARG_POINTER(0);
+		result = state->res;
+	}
+
+	/* turn the argument into jsonb in the normal function context */
 
 	if (PG_ARGISNULL(1))
 		ereport(ERROR,
@@ -1760,53 +1804,28 @@ jsonb_object_agg_transfn(PG_FUNCTION_ARGS)
 
 	val = PG_GETARG_DATUM(1);
 
-	jsonb_categorize_type(val_type,
-						  &tcategory, &outfuncoid);
-
 	memset(&elem, 0, sizeof(JsonbInState));
 
-	datum_to_jsonb(val, false, &elem, tcategory, outfuncoid, true);
+	datum_to_jsonb(val, false, &elem, state->key_category,
+				   state->key_output_func, true);
 
 	jbkey = JsonbValueToJsonb(elem.res);
 
-	val_type = get_fn_expr_argtype(fcinfo->flinfo, 2);
-
-	if (val_type == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("could not determine input data type")));
-
 	val = PG_ARGISNULL(2) ? (Datum) 0 : PG_GETARG_DATUM(2);
 
-	jsonb_categorize_type(val_type,
-						  &tcategory, &outfuncoid);
-
 	memset(&elem, 0, sizeof(JsonbInState));
 
-	datum_to_jsonb(val, PG_ARGISNULL(2), &elem, tcategory, outfuncoid, false);
+	datum_to_jsonb(val, PG_ARGISNULL(2), &elem, state->val_category,
+				   state->val_output_func, false);
 
 	jbval = JsonbValueToJsonb(elem.res);
 
+	it = JsonbIteratorInit(&jbkey->root);
+
 	/* switch to the aggregate context for accumulation operations */
 
 	oldcontext = MemoryContextSwitchTo(aggcontext);
 
-	/* set up the accumulator on the first go round */
-
-	if (PG_ARGISNULL(0))
-	{
-		result = palloc0(sizeof(JsonbInState));
-		result->res = pushJsonbValue(&result->parseState,
-									 WJB_BEGIN_OBJECT, NULL);
-
-	}
-	else
-	{
-		result = (JsonbInState *) PG_GETARG_POINTER(0);
-	}
-
-	it = JsonbIteratorInit(&jbkey->root);
-
 	/*
 	 * keys should be scalar, and we should have already checked for that
 	 * above when calling datum_to_jsonb, so we only need to look for these
@@ -1895,7 +1914,6 @@ jsonb_object_agg_transfn(PG_FUNCTION_ARGS)
 					v.val.numeric =
 					DatumGetNumeric(DirectFunctionCall1(numeric_uplus,
 											NumericGetDatum(v.val.numeric)));
-
 				}
 				result->res = pushJsonbValue(&result->parseState,
 											 single_scalar ? WJB_VALUE : type,
@@ -1908,13 +1926,13 @@ jsonb_object_agg_transfn(PG_FUNCTION_ARGS)
 
 	MemoryContextSwitchTo(oldcontext);
 
-	PG_RETURN_POINTER(result);
+	PG_RETURN_POINTER(state);
 }
 
 Datum
 jsonb_object_agg_finalfn(PG_FUNCTION_ARGS)
 {
-	JsonbInState *arg;
+	JsonbAggState *arg;
 	JsonbInState result;
 	Jsonb	   *out;
 
@@ -1924,21 +1942,20 @@ jsonb_object_agg_finalfn(PG_FUNCTION_ARGS)
 	if (PG_ARGISNULL(0))
 		PG_RETURN_NULL();		/* returns null iff no input values */
 
-	arg = (JsonbInState *) PG_GETARG_POINTER(0);
+	arg = (JsonbAggState *) PG_GETARG_POINTER(0);
 
 	/*
-	 * We need to do a shallow clone of the argument in case the final
-	 * function is called more than once, so we avoid changing the argument. A
-	 * shallow clone is sufficient as we aren't going to change any of the
-	 * values, just add the final object end marker.
+	 * We need to do a shallow clone of the argument's res field in case the
+	 * final function is called more than once, so we avoid changing the
+	 * it. A shallow clone is sufficient as we aren't going to change any of
+	 * the values, just add the final object end marker.
 	 */
 
-	result.parseState = clone_parse_state(arg->parseState);
+	result.parseState = clone_parse_state(arg->res->parseState);
 
 	result.res = pushJsonbValue(&result.parseState,
 								WJB_END_OBJECT, NULL);
 
-
 	out = JsonbValueToJsonb(result.res);
 
 	PG_RETURN_POINTER(out);