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

1 files changed, 2 insertions, 0 deletions

diff --git a/src/include/utils/json.h b/src/include/utils/json.h
index 6d7f1b387d1..79c1062e1bf 100644
--- a/src/include/utils/json.h
+++ b/src/include/utils/json.h
@@ -18,6 +18,8 @@
 
 /* functions in json.c */
 extern void escape_json(StringInfo buf, const char *str);
+extern void escape_json_with_len(StringInfo buf, const char *str, int len);
+extern void escape_json_text(StringInfo buf, const text *txt);
 extern char *JsonEncodeDateTime(char *buf, Datum value, Oid typid,
 								const int *tzp);
 extern bool to_json_is_immutable(Oid typoid);