SQL/JSON query functions

This introduces the SQL/JSON functions for querying JSON data using
jsonpath expressions. The functions are:

JSON_EXISTS()
JSON_QUERY()
JSON_VALUE()

All of these functions only operate on jsonb. The workaround for now is
to cast the argument to jsonb.

JSON_EXISTS() tests if the jsonpath expression applied to the jsonb
value yields any values. JSON_VALUE() must return a single value, and an
error occurs if it tries to return multiple values. JSON_QUERY() must
return a json object or array, and there are various WRAPPER options for
handling scalar or multi-value results. Both these functions have
options for handling EMPTY and ERROR conditions.

Nikita Glukhov

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru

1 files changed, 40 insertions, 5 deletions

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index ed698f788d..ac74333be5 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -1023,11 +1023,6 @@ typedef struct NUMProc
 			   *L_currency_symbol;
 } NUMProc;
 
-/* Return flags for DCH_from_char() */
-#define DCH_DATED	0x01
-#define DCH_TIMED	0x02
-#define DCH_ZONED	0x04
-
 /* ----------
  * Functions
  * ----------
@@ -6672,3 +6667,43 @@ float8_to_char(PG_FUNCTION_ARGS)
 	NUM_TOCHAR_finish;
 	PG_RETURN_TEXT_P(result);
 }
+
+int
+datetime_format_flags(const char *fmt_str, bool *have_error)
+{
+	bool		incache;
+	int			fmt_len = strlen(fmt_str);
+	int			result;
+	FormatNode *format;
+
+	if (fmt_len > DCH_CACHE_SIZE)
+	{
+		/*
+		 * Allocate new memory if format picture is bigger than static cache
+		 * and do not use cache (call parser always)
+		 */
+		incache = false;
+
+		format = (FormatNode *) palloc((fmt_len + 1) * sizeof(FormatNode));
+
+		parse_format(format, fmt_str, DCH_keywords,
+					 DCH_suff, DCH_index, DCH_FLAG, NULL);
+	}
+	else
+	{
+		/*
+		 * Use cache buffers
+		 */
+		DCHCacheEntry *ent = DCH_cache_fetch(fmt_str, false);
+
+		incache = true;
+		format = ent->format;
+	}
+
+	result = DCH_datetime_type(format, have_error);
+
+	if (!incache)
+		pfree(format);
+
+	return result;
+}