From 17a5871d9d58ea639b6d1ba4f0ce58462d55a33c Mon Sep 17 00:00:00 2001
From: David Rowley
Date: Sat, 27 Jul 2024 23:46:07 +1200
Subject: Optimize escaping of JSON strings

There were quite a few places where we either had a non-NUL-terminated
string or a text Datum which we needed to call escape_json() on.  Many of
these places required that a temporary string was created due to the fact
that escape_json() needs a NUL-terminated cstring.  For text types, those
first had to be converted to cstring before calling escape_json() on them.

Here we introduce two new functions to make escaping JSON more optimal:

escape_json_text() can be given a text Datum to append onto the given
buffer.  This is more optimal as it foregoes the need to convert the text
Datum into a cstring.  A temporary allocation is only required if the text
Datum needs to be detoasted.

escape_json_with_len() can be used when the length of the cstring is
already known or the given string isn't NUL-terminated.  Having this
allows various places which were creating a temporary NUL-terminated
string to just call escape_json_with_len() without any temporary memory
allocations.

Discussion: https://postgr.es/m/CAApHDvpLXwMZvbCKcdGfU9XQjGCDm7tFpRdTXuB9PVgpNUYfEQ@mail.gmail.com
Reviewed-by: Melih Mutlu, Heikki Linnakangas
---
 src/backend/utils/adt/jsonpath.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

(limited to 'src/backend/utils/adt/jsonpath.c')

diff --git a/src/backend/utils/adt/jsonpath.c b/src/backend/utils/adt/jsonpath.c
index 11e6193e964..0f691bc5f0f 100644
--- a/src/backend/utils/adt/jsonpath.c
+++ b/src/backend/utils/adt/jsonpath.c
@@ -523,6 +523,8 @@ printJsonPathItem(StringInfo buf, JsonPathItem *v, bool inKey,
 {
 	JsonPathItem elem;
 	int			i;
+	int32		len;
+	char	   *str;
 
 	check_stack_depth();
 	CHECK_FOR_INTERRUPTS();
@@ -533,7 +535,8 @@ printJsonPathItem(StringInfo buf, JsonPathItem *v, bool inKey,
 			appendStringInfoString(buf, "null");
 			break;
 		case jpiString:
-			escape_json(buf, jspGetString(v, NULL));
+			str = jspGetString(v, &len);
+			escape_json_with_len(buf, str, len);
 			break;
 		case jpiNumeric:
 			if (jspHasNext(v))
@@ -662,7 +665,8 @@ printJsonPathItem(StringInfo buf, JsonPathItem *v, bool inKey,
 		case jpiKey:
 			if (inKey)
 				appendStringInfoChar(buf, '.');
-			escape_json(buf, jspGetString(v, NULL));
+			str = jspGetString(v, &len);
+			escape_json_with_len(buf, str, len);
 			break;
 		case jpiCurrent:
 			Assert(!inKey);
@@ -674,7 +678,8 @@ printJsonPathItem(StringInfo buf, JsonPathItem *v, bool inKey,
 			break;
 		case jpiVariable:
 			appendStringInfoChar(buf, '$');
-			escape_json(buf, jspGetString(v, NULL));
+			str = jspGetString(v, &len);
+			escape_json_with_len(buf, str, len);
 			break;
 		case jpiFilter:
 			appendStringInfoString(buf, "?(");
@@ -732,7 +737,9 @@ printJsonPathItem(StringInfo buf, JsonPathItem *v, bool inKey,
 
 			appendStringInfoString(buf, " like_regex ");
 
-			escape_json(buf, v->content.like_regex.pattern);
+			escape_json_with_len(buf,
+								 v->content.like_regex.pattern,
+								 v->content.like_regex.patternlen);
 
 			if (v->content.like_regex.flags)
 			{
-- 
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