Use stack allocated StringInfoDatas, where possible

Various places that were using StringInfo but didn't need that
StringInfo to exist beyond the scope of the function were using
makeStringInfo(), which allocates both a StringInfoData and the buffer it
uses as two separate allocations.  It's more efficient for these cases to
use a StringInfoData on the stack and initialize it with initStringInfo(),
which only allocates the string buffer.  This also simplifies the cleanup,
in a few cases.

Author: Mats Kindahl <mats.kindahl@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/4379aac8-26f1-42f2-a356-ff0e886228d3@gmail.com

7 files changed, 87 insertions, 75 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 88a612b041d..06dd62f0008 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -631,13 +631,13 @@ Datum
 array_to_json(PG_FUNCTION_ARGS)
 {
 	Datum		array = PG_GETARG_DATUM(0);
-	StringInfo	result;
+	StringInfoData result;
 
-	result = makeStringInfo();
+	initStringInfo(&result);
 
-	array_to_json_internal(array, result, false);
+	array_to_json_internal(array, &result, false);
 
-	PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
+	PG_RETURN_TEXT_P(cstring_to_text_with_len(result.data, result.len));
 }
 
 /*
@@ -648,13 +648,13 @@ array_to_json_pretty(PG_FUNCTION_ARGS)
 {
 	Datum		array = PG_GETARG_DATUM(0);
 	bool		use_line_feeds = PG_GETARG_BOOL(1);
-	StringInfo	result;
+	StringInfoData result;
 
-	result = makeStringInfo();
+	initStringInfo(&result);
 
-	array_to_json_internal(array, result, use_line_feeds);
+	array_to_json_internal(array, &result, use_line_feeds);
 
-	PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
+	PG_RETURN_TEXT_P(cstring_to_text_with_len(result.data, result.len));
 }
 
 /*
@@ -664,13 +664,13 @@ Datum
 row_to_json(PG_FUNCTION_ARGS)
 {
 	Datum		array = PG_GETARG_DATUM(0);
-	StringInfo	result;
+	StringInfoData result;
 
-	result = makeStringInfo();
+	initStringInfo(&result);
 
-	composite_to_json(array, result, false);
+	composite_to_json(array, &result, false);
 
-	PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
+	PG_RETURN_TEXT_P(cstring_to_text_with_len(result.data, result.len));
 }
 
 /*
@@ -681,13 +681,13 @@ row_to_json_pretty(PG_FUNCTION_ARGS)
 {
 	Datum		array = PG_GETARG_DATUM(0);
 	bool		use_line_feeds = PG_GETARG_BOOL(1);
-	StringInfo	result;
+	StringInfoData result;
 
-	result = makeStringInfo();
+	initStringInfo(&result);
 
-	composite_to_json(array, result, use_line_feeds);
+	composite_to_json(array, &result, use_line_feeds);
 
-	PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
+	PG_RETURN_TEXT_P(cstring_to_text_with_len(result.data, result.len));
 }
 
 /*
@@ -763,12 +763,13 @@ to_json(PG_FUNCTION_ARGS)
 Datum
 datum_to_json(Datum val, JsonTypeCategory tcategory, Oid outfuncoid)
 {
-	StringInfo	result = makeStringInfo();
+	StringInfoData result;
 
-	datum_to_json_internal(val, false, result, tcategory, outfuncoid,
+	initStringInfo(&result);
+	datum_to_json_internal(val, false, &result, tcategory, outfuncoid,
 						   false);
 
-	return PointerGetDatum(cstring_to_text_with_len(result->data, result->len));
+	return PointerGetDatum(cstring_to_text_with_len(result.data, result.len));
 }
 
 /*
@@ -1347,25 +1348,25 @@ json_build_array_worker(int nargs, const Datum *args, const bool *nulls, const O
 {
 	int			i;
 	const char *sep = "";
-	StringInfo	result;
+	StringInfoData result;
 
-	result = makeStringInfo();
+	initStringInfo(&result);
 
-	appendStringInfoChar(result, '[');
+	appendStringInfoChar(&result, '[');
 
 	for (i = 0; i < nargs; i++)
 	{
 		if (absent_on_null && nulls[i])
 			continue;
 
-		appendStringInfoString(result, sep);
+		appendStringInfoString(&result, sep);
 		sep = ", ";
-		add_json(args[i], nulls[i], result, types[i], false);
+		add_json(args[i], nulls[i], &result, types[i], false);
 	}
 
-	appendStringInfoChar(result, ']');
+	appendStringInfoChar(&result, ']');
 
-	return PointerGetDatum(cstring_to_text_with_len(result->data, result->len));
+	return PointerGetDatum(cstring_to_text_with_len(result.data, result.len));
 }
 
 /*
diff --git a/src/backend/utils/adt/jsonb.c b/src/backend/utils/adt/jsonb.c
index da94d424d61..9399cdb491a 100644
--- a/src/backend/utils/adt/jsonb.c
+++ b/src/backend/utils/adt/jsonb.c
@@ -125,15 +125,16 @@ jsonb_send(PG_FUNCTION_ARGS)
 {
 	Jsonb	   *jb = PG_GETARG_JSONB_P(0);
 	StringInfoData buf;
-	StringInfo	jtext = makeStringInfo();
+	StringInfoData jtext;
 	int			version = 1;
 
-	(void) JsonbToCString(jtext, &jb->root, VARSIZE(jb));
+	initStringInfo(&jtext);
+	(void) JsonbToCString(&jtext, &jb->root, VARSIZE(jb));
 
 	pq_begintypsend(&buf);
 	pq_sendint8(&buf, version);
-	pq_sendtext(&buf, jtext->data, jtext->len);
-	destroyStringInfo(jtext);
+	pq_sendtext(&buf, jtext.data, jtext.len);
+	pfree(jtext.data);
 
 	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
 }
diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 41862872e8a..8898f0f90a1 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -4507,14 +4507,16 @@ json_strip_nulls(PG_FUNCTION_ARGS)
 	text	   *json = PG_GETARG_TEXT_PP(0);
 	bool		strip_in_arrays = PG_NARGS() == 2 ? PG_GETARG_BOOL(1) : false;
 	StripnullState *state;
+	StringInfoData strbuf;
 	JsonLexContext lex;
 	JsonSemAction *sem;
 
 	state = palloc0(sizeof(StripnullState));
 	sem = palloc0(sizeof(JsonSemAction));
+	initStringInfo(&strbuf);
 
 	state->lex = makeJsonLexContext(&lex, json, true);
-	state->strval = makeStringInfo();
+	state->strval = &strbuf;
 	state->skip_next_null = false;
 	state->strip_in_arrays = strip_in_arrays;
 
@@ -4607,11 +4609,12 @@ Datum
 jsonb_pretty(PG_FUNCTION_ARGS)
 {
 	Jsonb	   *jb = PG_GETARG_JSONB_P(0);
-	StringInfo	str = makeStringInfo();
+	StringInfoData str;
 
-	JsonbToCStringIndent(str, &jb->root, VARSIZE(jb));
+	initStringInfo(&str);
+	JsonbToCStringIndent(&str, &jb->root, VARSIZE(jb));
 
-	PG_RETURN_TEXT_P(cstring_to_text_with_len(str->data, str->len));
+	PG_RETURN_TEXT_P(cstring_to_text_with_len(str.data, str.len));
 }
 
 /*
@@ -5846,7 +5849,7 @@ transform_jsonb_string_values(Jsonb *jsonb, void *action_state,
  * Iterate over a json, and apply a specified JsonTransformStringValuesAction
  * to every string value or element. Any necessary context for a
  * JsonTransformStringValuesAction can be passed in the action_state variable.
- * Function returns a StringInfo, which is a copy of an original json with
+ * Function returns a Text Datum, which is a copy of an original json with
  * transformed values.
  */
 text *
@@ -5856,9 +5859,12 @@ transform_json_string_values(text *json, void *action_state,
 	JsonLexContext lex;
 	JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
 	TransformJsonStringValuesState *state = palloc0(sizeof(TransformJsonStringValuesState));
+	StringInfoData strbuf;
+
+	initStringInfo(&strbuf);
 
 	state->lex = makeJsonLexContext(&lex, json, true);
-	state->strval = makeStringInfo();
+	state->strval = &strbuf;
 	state->action = transform_action;
 	state->action_state = action_state;
 
diff --git a/src/backend/utils/adt/multirangetypes.c b/src/backend/utils/adt/multirangetypes.c
index 84733dc5019..95e9539591e 100644
--- a/src/backend/utils/adt/multirangetypes.c
+++ b/src/backend/utils/adt/multirangetypes.c
@@ -378,17 +378,18 @@ multirange_send(PG_FUNCTION_ARGS)
 {
 	MultirangeType *multirange = PG_GETARG_MULTIRANGE_P(0);
 	Oid			mltrngtypoid = MultirangeTypeGetOid(multirange);
-	StringInfo	buf = makeStringInfo();
+	StringInfoData buf;
 	RangeType **ranges;
 	int32		range_count;
 	MultirangeIOData *cache;
 
+	initStringInfo(&buf);
 	cache = get_multirange_io_data(fcinfo, mltrngtypoid, IOFunc_send);
 
 	/* construct output */
-	pq_begintypsend(buf);
+	pq_begintypsend(&buf);
 
-	pq_sendint32(buf, multirange->rangeCount);
+	pq_sendint32(&buf, multirange->rangeCount);
 
 	multirange_deserialize(cache->typcache->rngtype, multirange, &range_count, &ranges);
 	for (int i = 0; i < range_count; i++)
@@ -399,11 +400,11 @@ multirange_send(PG_FUNCTION_ARGS)
 		range = RangeTypePGetDatum(ranges[i]);
 		outputbytes = SendFunctionCall(&cache->typioproc, range);
 
-		pq_sendint32(buf, VARSIZE(outputbytes) - VARHDRSZ);
-		pq_sendbytes(buf, VARDATA(outputbytes), VARSIZE(outputbytes) - VARHDRSZ);
+		pq_sendint32(&buf, VARSIZE(outputbytes) - VARHDRSZ);
+		pq_sendbytes(&buf, VARDATA(outputbytes), VARSIZE(outputbytes) - VARHDRSZ);
 	}
 
-	PG_RETURN_BYTEA_P(pq_endtypsend(buf));
+	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
 }
 
 /*
diff --git a/src/backend/utils/adt/rangetypes.c b/src/backend/utils/adt/rangetypes.c
index 0b2ad8b0975..0e451e4693b 100644
--- a/src/backend/utils/adt/rangetypes.c
+++ b/src/backend/utils/adt/rangetypes.c
@@ -264,7 +264,7 @@ Datum
 range_send(PG_FUNCTION_ARGS)
 {
 	RangeType  *range = PG_GETARG_RANGE_P(0);
-	StringInfo	buf = makeStringInfo();
+	StringInfoData buf;
 	RangeIOData *cache;
 	char		flags;
 	RangeBound	lower;
@@ -273,6 +273,8 @@ range_send(PG_FUNCTION_ARGS)
 
 	check_stack_depth();		/* recurses when subtype is a range type */
 
+	initStringInfo(&buf);
+
 	cache = get_range_io_data(fcinfo, RangeTypeGetOid(range), IOFunc_send);
 
 	/* deserialize */
@@ -280,9 +282,9 @@ range_send(PG_FUNCTION_ARGS)
 	flags = range_get_flags(range);
 
 	/* construct output */
-	pq_begintypsend(buf);
+	pq_begintypsend(&buf);
 
-	pq_sendbyte(buf, flags);
+	pq_sendbyte(&buf, flags);
 
 	if (RANGE_HAS_LBOUND(flags))
 	{
@@ -290,8 +292,8 @@ range_send(PG_FUNCTION_ARGS)
 		uint32		bound_len = VARSIZE(bound) - VARHDRSZ;
 		char	   *bound_data = VARDATA(bound);
 
-		pq_sendint32(buf, bound_len);
-		pq_sendbytes(buf, bound_data, bound_len);
+		pq_sendint32(&buf, bound_len);
+		pq_sendbytes(&buf, bound_data, bound_len);
 	}
 
 	if (RANGE_HAS_UBOUND(flags))
@@ -300,11 +302,11 @@ range_send(PG_FUNCTION_ARGS)
 		uint32		bound_len = VARSIZE(bound) - VARHDRSZ;
 		char	   *bound_data = VARDATA(bound);
 
-		pq_sendint32(buf, bound_len);
-		pq_sendbytes(buf, bound_data, bound_len);
+		pq_sendint32(&buf, bound_len);
+		pq_sendbytes(&buf, bound_data, bound_len);
 	}
 
-	PG_RETURN_BYTEA_P(pq_endtypsend(buf));
+	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
 }
 
 /*
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 5398679cce2..556ab057e5a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -13711,25 +13711,26 @@ char *
 get_range_partbound_string(List *bound_datums)
 {
 	deparse_context context;
-	StringInfo	buf = makeStringInfo();
+	StringInfoData buf;
 	ListCell   *cell;
 	char	   *sep;
 
+	initStringInfo(&buf);
 	memset(&context, 0, sizeof(deparse_context));
-	context.buf = buf;
+	context.buf = &buf;
 
-	appendStringInfoChar(buf, '(');
+	appendStringInfoChar(&buf, '(');
 	sep = "";
 	foreach(cell, bound_datums)
 	{
 		PartitionRangeDatum *datum =
 			lfirst_node(PartitionRangeDatum, cell);
 
-		appendStringInfoString(buf, sep);
+		appendStringInfoString(&buf, sep);
 		if (datum->kind == PARTITION_RANGE_DATUM_MINVALUE)
-			appendStringInfoString(buf, "MINVALUE");
+			appendStringInfoString(&buf, "MINVALUE");
 		else if (datum->kind == PARTITION_RANGE_DATUM_MAXVALUE)
-			appendStringInfoString(buf, "MAXVALUE");
+			appendStringInfoString(&buf, "MAXVALUE");
 		else
 		{
 			Const	   *val = castNode(Const, datum->value);
@@ -13738,7 +13739,7 @@ get_range_partbound_string(List *bound_datums)
 		}
 		sep = ", ";
 	}
-	appendStringInfoChar(buf, ')');
+	appendStringInfoChar(&buf, ')');
 
-	return buf->data;
+	return buf.data;
 }
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 35c915573a1..41e775570ec 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2133,7 +2133,7 @@ xml_errorHandler(void *data, PgXmlErrorPtr error)
 						   node->type == XML_ELEMENT_NODE) ? node->name : NULL;
 	int			domain = error->domain;
 	int			level = error->level;
-	StringInfo	errorBuf;
+	StringInfoData errorBuf;
 
 	/*
 	 * Defend against someone passing us a bogus context struct.
@@ -2210,16 +2210,16 @@ xml_errorHandler(void *data, PgXmlErrorPtr error)
 	}
 
 	/* Prepare error message in errorBuf */
-	errorBuf = makeStringInfo();
+	initStringInfo(&errorBuf);
 
 	if (error->line > 0)
-		appendStringInfo(errorBuf, "line %d: ", error->line);
+		appendStringInfo(&errorBuf, "line %d: ", error->line);
 	if (name != NULL)
-		appendStringInfo(errorBuf, "element %s: ", name);
+		appendStringInfo(&errorBuf, "element %s: ", name);
 	if (error->message != NULL)
-		appendStringInfoString(errorBuf, error->message);
+		appendStringInfoString(&errorBuf, error->message);
 	else
-		appendStringInfoString(errorBuf, "(no message provided)");
+		appendStringInfoString(&errorBuf, "(no message provided)");
 
 	/*
 	 * Append context information to errorBuf.
@@ -2237,11 +2237,11 @@ xml_errorHandler(void *data, PgXmlErrorPtr error)
 		xmlGenericErrorFunc errFuncSaved = xmlGenericError;
 		void	   *errCtxSaved = xmlGenericErrorContext;
 
-		xmlSetGenericErrorFunc(errorBuf,
+		xmlSetGenericErrorFunc(&errorBuf,
 							   (xmlGenericErrorFunc) appendStringInfo);
 
 		/* Add context information to errorBuf */
-		appendStringInfoLineSeparator(errorBuf);
+		appendStringInfoLineSeparator(&errorBuf);
 
 		xmlParserPrintFileContext(input);
 
@@ -2250,7 +2250,7 @@ xml_errorHandler(void *data, PgXmlErrorPtr error)
 	}
 
 	/* Get rid of any trailing newlines in errorBuf */
-	chopStringInfoNewlines(errorBuf);
+	chopStringInfoNewlines(&errorBuf);
 
 	/*
 	 * Legacy error handling mode.  err_occurred is never set, we just add the
@@ -2263,10 +2263,10 @@ xml_errorHandler(void *data, PgXmlErrorPtr error)
 	if (xmlerrcxt->strictness == PG_XML_STRICTNESS_LEGACY)
 	{
 		appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
-		appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf->data,
-							   errorBuf->len);
+		appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf.data,
+							   errorBuf.len);
 
-		destroyStringInfo(errorBuf);
+		pfree(errorBuf.data);
 		return;
 	}
 
@@ -2281,23 +2281,23 @@ xml_errorHandler(void *data, PgXmlErrorPtr error)
 	if (level >= XML_ERR_ERROR)
 	{
 		appendStringInfoLineSeparator(&xmlerrcxt->err_buf);
-		appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf->data,
-							   errorBuf->len);
+		appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf.data,
+							   errorBuf.len);
 
 		xmlerrcxt->err_occurred = true;
 	}
 	else if (level >= XML_ERR_WARNING)
 	{
 		ereport(WARNING,
-				(errmsg_internal("%s", errorBuf->data)));
+				(errmsg_internal("%s", errorBuf.data)));
 	}
 	else
 	{
 		ereport(NOTICE,
-				(errmsg_internal("%s", errorBuf->data)));
+				(errmsg_internal("%s", errorBuf.data)));
 	}
 
-	destroyStringInfo(errorBuf);
+	pfree(errorBuf.data);
 }