diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index be7b00b1f32..e397386bf24 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -10095,7 +10095,7 @@ table2-mapping
json
- Returns JSON object pointed to by path_elems.
+ Returns JSON value pointed to by path_elems.
json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}','f4')
{"f5":99,"f6":"foo"}
@@ -10109,7 +10109,7 @@ table2-mapping
text
- Returns JSON object pointed to by path_elems.
+ Returns JSON value pointed to by path_elems.
json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}','f4', 'f6')
foo
@@ -10192,7 +10192,7 @@ table2-mapping
SETOF json
- Expands a JSON array to a set of JSON elements.
+ Expands a JSON array to a set of JSON values.
json_array_elements('[1,true, [2,false]]')
@@ -10205,6 +10205,23 @@ table2-mapping
+
+
+
+ json_typeof
+
+ json_typeof(json)
+
+ text
+
+ Returns the type of the outermost JSON value as a text string. The types are
+ object, array, string, number,
+ boolean, and null. (See note below regarding the
+ distinction between a JSON null and a SQL NULL.)
+
+ json_typeof('-123.4')
+ number
+
@@ -10237,6 +10254,14 @@ table2-mapping
+
+
+ The json_typeof function's null return value should not be confused
+ with a SQL NULL. While calling json_typeof('null'::json) will return null,
+ calling json_typeof(NULL::json) will return a SQL NULL.
+
+
+
See also about the aggregate
function json_agg which aggregates record
diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 9f3f5d4feb4..b6199fbf68d 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -1826,3 +1826,55 @@ escape_json(StringInfo buf, const char *str)
}
appendStringInfoCharMacro(buf, '\"');
}
+
+/*
+ * SQL function json_typeof(json) -> text
+ *
+ * Returns the type of the outermost JSON value as TEXT. Possible types are
+ * "object", "array", "string", "number", "boolean", and "null".
+ *
+ * Performs a single call to json_lex() to get the first token of the supplied
+ * value. This initial token uniquely determines the value's type. As our
+ * input must already have been validated by json_in() or json_recv(), the
+ * initial token should never be JSON_TOKEN_OBJECT_END, JSON_TOKEN_ARRAY_END,
+ * JSON_TOKEN_COLON, JSON_TOKEN_COMMA, or JSON_TOKEN_END.
+ */
+Datum
+json_typeof(PG_FUNCTION_ARGS)
+{
+ text *json = PG_GETARG_TEXT_P(0);
+
+ JsonLexContext *lex = makeJsonLexContext(json, false);
+ JsonTokenType tok;
+ char *type;
+
+ /* Lex exactly one token from the input and check its type. */
+ json_lex(lex);
+ tok = lex_peek(lex);
+ switch (tok)
+ {
+ case JSON_TOKEN_OBJECT_START:
+ type = "object";
+ break;
+ case JSON_TOKEN_ARRAY_START:
+ type = "array";
+ break;
+ case JSON_TOKEN_STRING:
+ type = "string";
+ break;
+ case JSON_TOKEN_NUMBER:
+ type = "number";
+ break;
+ case JSON_TOKEN_TRUE:
+ case JSON_TOKEN_FALSE:
+ type = "boolean";
+ break;
+ case JSON_TOKEN_NULL:
+ type = "null";
+ break;
+ default:
+ elog(ERROR, "unexpected json token: %d", tok);
+ }
+
+ PG_RETURN_TEXT_P(cstring_to_text(type));
+}
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 5b2749c417e..58ed8a3fe99 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 201310091
+#define CATALOG_VERSION_NO 201310101
#endif
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 3e523989c38..08586ae064a 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4150,6 +4150,8 @@ DATA(insert OID = 3960 ( json_populate_record PGNSP PGUID 12 1 0 0 0 f f f f
DESCR("get record fields from a json object");
DATA(insert OID = 3961 ( json_populate_recordset PGNSP PGUID 12 1 100 0 0 f f f f f t s 3 0 2283 "2283 114 16" _null_ _null_ _null_ _null_ json_populate_recordset _null_ _null_ _null_ ));
DESCR("get set of records with fields from a json array of objects");
+DATA(insert OID = 3968 ( json_typeof PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "114" _null_ _null_ _null_ _null_ json_typeof _null_ _null_ _null_ ));
+DESCR("get the type of a json value");
/* uuid */
DATA(insert OID = 2952 ( uuid_in PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 2950 "2275" _null_ _null_ _null_ _null_ uuid_in _null_ _null_ _null_ ));
diff --git a/src/include/utils/json.h b/src/include/utils/json.h
index 4845f5f6183..62fd7c78295 100644
--- a/src/include/utils/json.h
+++ b/src/include/utils/json.h
@@ -33,6 +33,8 @@ extern Datum json_agg_finalfn(PG_FUNCTION_ARGS);
extern void escape_json(StringInfo buf, const char *str);
+extern Datum json_typeof(PG_FUNCTION_ARGS);
+
/* functions in jsonfuncs.c */
extern Datum json_object_field(PG_FUNCTION_ARGS);
extern Datum json_object_field_text(PG_FUNCTION_ARGS);
diff --git a/src/test/regress/expected/json.out b/src/test/regress/expected/json.out
index 1a357988e47..d7e96941322 100644
--- a/src/test/regress/expected/json.out
+++ b/src/test/regress/expected/json.out
@@ -962,3 +962,32 @@ select json '{ "a": "null \u0000 escape" }' ->> 'a' as not_unescaped;
null \u0000 escape
(1 row)
+--json_typeof() function
+select value, json_typeof(value)
+ from (values (json '123.4'),
+ (json '-1'),
+ (json '"foo"'),
+ (json 'true'),
+ (json 'false'),
+ (json 'null'),
+ (json '[1, 2, 3]'),
+ (json '[]'),
+ (json '{"x":"foo", "y":123}'),
+ (json '{}'),
+ (NULL::json))
+ as data(value);
+ value | json_typeof
+----------------------+-------------
+ 123.4 | number
+ -1 | number
+ "foo" | string
+ true | boolean
+ false | boolean
+ null | null
+ [1, 2, 3] | array
+ [] | array
+ {"x":"foo", "y":123} | object
+ {} | object
+ |
+(11 rows)
+
diff --git a/src/test/regress/expected/json_1.out b/src/test/regress/expected/json_1.out
index 201fcb2d204..c9710d22e4c 100644
--- a/src/test/regress/expected/json_1.out
+++ b/src/test/regress/expected/json_1.out
@@ -958,3 +958,32 @@ select json '{ "a": "null \u0000 escape" }' ->> 'a' as not_unescaped;
null \u0000 escape
(1 row)
+--json_typeof() function
+select value, json_typeof(value)
+ from (values (json '123.4'),
+ (json '-1'),
+ (json '"foo"'),
+ (json 'true'),
+ (json 'false'),
+ (json 'null'),
+ (json '[1, 2, 3]'),
+ (json '[]'),
+ (json '{"x":"foo", "y":123}'),
+ (json '{}'),
+ (NULL::json))
+ as data(value);
+ value | json_typeof
+----------------------+-------------
+ 123.4 | number
+ -1 | number
+ "foo" | string
+ true | boolean
+ false | boolean
+ null | null
+ [1, 2, 3] | array
+ [] | array
+ {"x":"foo", "y":123} | object
+ {} | object
+ |
+(11 rows)
+
diff --git a/src/test/regress/sql/json.sql b/src/test/regress/sql/json.sql
index 4c4c6958bbd..ff7675fad0d 100644
--- a/src/test/regress/sql/json.sql
+++ b/src/test/regress/sql/json.sql
@@ -310,3 +310,18 @@ select json '{ "a": "\ude04X" }' -> 'a'; -- orphan low surrogate
select json '{ "a": "the Copyright \u00a9 sign" }' ->> 'a' as correct_in_utf8;
select json '{ "a": "dollar \u0024 character" }' ->> 'a' as correct_everywhere;
select json '{ "a": "null \u0000 escape" }' ->> 'a' as not_unescaped;
+
+--json_typeof() function
+select value, json_typeof(value)
+ from (values (json '123.4'),
+ (json '-1'),
+ (json '"foo"'),
+ (json 'true'),
+ (json 'false'),
+ (json 'null'),
+ (json '[1, 2, 3]'),
+ (json '[]'),
+ (json '{"x":"foo", "y":123}'),
+ (json '{}'),
+ (NULL::json))
+ as data(value);