Add json_array_elements_text function.

This was a notable omission from the json functions added in 9.3 and
there have been numerous complaints about its absence.

Laurence Rowe.

doc/src/sgml/func.sgml

@@ -10280,6 +10280,27 @@ table2-mapping
  1
  true
  [2,false]
+</programlisting>
+       </entry>
+      </row>
+      <row>
+       <entry>
+         <indexterm>
+          <primary>json_array_elements_text</primary>
+         </indexterm>
+         <literal>json_array_elements_text(json)</literal>
+       </entry>
+       <entry><type>SETOF json</type></entry>
+       <entry>
+         Expands a JSON array to a set of text values.
+       </entry>
+       <entry><literal>json_array_elements_text('["foo", "bar"]')</literal></entry>
+       <entry>
+<programlisting>
+   value
+-----------
+ foo
+ bar
 </programlisting>
        </entry>
       </row>

src/backend/utils/adt/jsonfuncs.c

@@ -66,6 +66,9 @@ static void each_object_field_end(void *state, char *fname, bool isnull);
 static void each_array_start(void *state);
 static void each_scalar(void *state, char *token, JsonTokenType tokentype);
 
+/* common worker for json_each* functions */
+static inline Datum elements_worker(PG_FUNCTION_ARGS, bool as_text);
+
 /* semantic action functions for json_array_elements */
 static void elements_object_start(void *state);
 static void elements_array_element_start(void *state, bool isnull);
@@ -165,6 +168,9 @@ typedef struct ElementsState
 	TupleDesc	ret_tdesc;
 	MemoryContext tmp_cxt;
 	char	   *result_start;
+	bool		normalize_results;
+	bool		next_scalar;
+	char	   *normalized_scalar;
 } ElementsState;
 
 /* state for get_json_object_as_hash */
@@ -1069,7 +1075,7 @@ each_scalar(void *state, char *token, JsonTokenType tokentype)
 }
 
 /*
- * SQL function json_array_elements
+ * SQL functions json_array_elements and json_array_elements_text
  *
  * get the elements from a json array
  *
@@ -1077,11 +1083,23 @@ each_scalar(void *state, char *token, JsonTokenType tokentype)
  */
 Datum
 json_array_elements(PG_FUNCTION_ARGS)
+{
+	return elements_worker(fcinfo, false);
+}
+
+Datum
+json_array_elements_text(PG_FUNCTION_ARGS)
+{
+	return elements_worker(fcinfo, true);
+}
+
+static inline Datum
+elements_worker(PG_FUNCTION_ARGS, bool as_text)
 {
 	text	   *json = PG_GETARG_TEXT_P(0);
 
-	/* elements doesn't need any escaped strings, so use false here */
-	JsonLexContext *lex = makeJsonLexContext(json, false);
+	/* elements only needs escaped strings when as_text */
+	JsonLexContext *lex = makeJsonLexContext(json, as_text);
 	JsonSemAction *sem;
 	ReturnSetInfo *rsi;
 	MemoryContext old_cxt;
@@ -1124,6 +1142,9 @@ json_array_elements(PG_FUNCTION_ARGS)
 	sem->array_element_start = elements_array_element_start;
 	sem->array_element_end = elements_array_element_end;
 
+	state->normalize_results = as_text;
+	state->next_scalar = false;
+
 	state->lex = lex;
 	state->tmp_cxt = AllocSetContextCreate(CurrentMemoryContext,
 										 "json_array_elements temporary cxt",
@@ -1146,7 +1167,17 @@ elements_array_element_start(void *state, bool isnull)
 
 	/* save a pointer to where the value starts */
 	if (_state->lex->lex_level == 1)
-		_state->result_start = _state->lex->token_start;
+	{
+		/*
+		 * next_scalar will be reset in the array_element_end handler, and
+		 * since we know the value is a scalar there is no danger of it being
+		 * on while recursing down the tree.
+		 */
+		if (_state->normalize_results && _state->lex->token_type == JSON_TOKEN_STRING)
+			_state->next_scalar = true;
+		else
+			_state->result_start = _state->lex->token_start;
+	}
 }
 
 static void
@@ -1158,7 +1189,7 @@ elements_array_element_end(void *state, bool isnull)
 	text	   *val;
 	HeapTuple	tuple;
 	Datum		values[1];
-	static bool nulls[1] = {false};
+	bool nulls[1] = {false};
 
 	/* skip over nested objects */
 	if (_state->lex->lex_level != 1)
@@ -1167,10 +1198,23 @@ elements_array_element_end(void *state, bool isnull)
 	/* use the tmp context so we can clean up after each tuple is done */
 	old_cxt = MemoryContextSwitchTo(_state->tmp_cxt);
 
-	len = _state->lex->prev_token_terminator - _state->result_start;
-	val = cstring_to_text_with_len(_state->result_start, len);
+	if (isnull && _state->normalize_results)
+	{
+		nulls[0] = true;
+		values[0] = (Datum) NULL;
+	}
+	else if (_state->next_scalar)
+	{
+		values[0] = CStringGetTextDatum(_state->normalized_scalar);
+		_state->next_scalar = false;
+	}
+	else
+	{
+		len = _state->lex->prev_token_terminator - _state->result_start;
+		val = cstring_to_text_with_len(_state->result_start, len);
+		values[0] = PointerGetDatum(val);
+	}
 
-	values[0] = PointerGetDatum(val);
 
 	tuple = heap_form_tuple(_state->ret_tdesc, values, nulls);
 
@@ -1204,10 +1248,9 @@ elements_scalar(void *state, char *token, JsonTokenType tokentype)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("cannot call json_array_elements on a scalar")));
 
-	/*
-	 * json_array_elements always returns json, so there's no need to think
-	 * about de-escaped values here.
-	 */
+	/* supply de-escaped value if required */
+	if (_state->next_scalar)
+		_state->normalized_scalar = token;
 }
 
 /*

src/include/catalog/pg_proc.h

@@ -4185,6 +4185,8 @@ DATA(insert OID = 3205 (  json_to_recordset  PGNSP PGUID 12 1 100 0 0 f f f f f
 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");
+DATA(insert OID = 3969 (  json_array_elements_text	PGNSP PGUID 12 1 100 0 0 f f f f t t i 1 0 25 "114" "{114,25}" "{i,o}" "{from_json,value}" _null_ json_array_elements_text _null_ _null_ _null_ ));
+DESCR("elements of json array");
 
 /* 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_ ));

src/include/utils/json.h

@@ -58,6 +58,7 @@ extern Datum json_array_length(PG_FUNCTION_ARGS);
 extern Datum json_each(PG_FUNCTION_ARGS);
 extern Datum json_each_text(PG_FUNCTION_ARGS);
 extern Datum json_array_elements(PG_FUNCTION_ARGS);
+extern Datum json_array_elements_text(PG_FUNCTION_ARGS);
 extern Datum json_populate_record(PG_FUNCTION_ARGS);
 extern Datum json_populate_recordset(PG_FUNCTION_ARGS);
 extern Datum json_to_record(PG_FUNCTION_ARGS);

src/test/regress/expected/json.out

@@ -801,7 +801,7 @@ select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>'{f2,1}';
 (1 row)
 
 -- array_elements
-select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]');
+select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]');
   json_array_elements  
 -----------------------
  1
@@ -810,9 +810,10 @@ select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]'
  null
  {"f1":1,"f2":[7,8,9]}
  false
-(6 rows)
+ "stringy"
+(7 rows)
 
-select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]') q;
+select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]') q;
          value         
 -----------------------
  1
@@ -821,7 +822,32 @@ select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},
  null
  {"f1":1,"f2":[7,8,9]}
  false
-(6 rows)
+ "stringy"
+(7 rows)
+
+select json_array_elements_text('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]');
+ json_array_elements_text 
+--------------------------
+ 1
+ true
+ [1,[2,3]]
+ 
+ {"f1":1,"f2":[7,8,9]}
+ false
+ stringy
+(7 rows)
+
+select * from json_array_elements_text('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]') q;
+         value         
+-----------------------
+ 1
+ true
+ [1,[2,3]]
+ 
+ {"f1":1,"f2":[7,8,9]}
+ false
+ stringy
+(7 rows)
 
 -- populate_record
 create type jpop as (a text, b int, c timestamp);

src/test/regress/expected/json_1.out

@@ -801,7 +801,7 @@ select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>'{f2,1}';
 (1 row)
 
 -- array_elements
-select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]');
+select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]');
   json_array_elements  
 -----------------------
  1
@@ -810,9 +810,10 @@ select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]'
  null
  {"f1":1,"f2":[7,8,9]}
  false
-(6 rows)
+ "stringy"
+(7 rows)
 
-select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]') q;
+select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]') q;
          value         
 -----------------------
  1
@@ -821,7 +822,32 @@ select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},
  null
  {"f1":1,"f2":[7,8,9]}
  false
-(6 rows)
+ "stringy"
+(7 rows)
+
+select json_array_elements_text('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]');
+ json_array_elements_text 
+--------------------------
+ 1
+ true
+ [1,[2,3]]
+ 
+ {"f1":1,"f2":[7,8,9]}
+ false
+ stringy
+(7 rows)
+
+select * from json_array_elements_text('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]') q;
+         value         
+-----------------------
+ 1
+ true
+ [1,[2,3]]
+ 
+ {"f1":1,"f2":[7,8,9]}
+ false
+ stringy
+(7 rows)
 
 -- populate_record
 create type jpop as (a text, b int, c timestamp);

src/test/regress/sql/json.sql

@@ -265,8 +265,10 @@ select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>'{f2,1}';
 
 -- array_elements
 
-select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]');
-select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]') q;
+select json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]');
+select * from json_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]') q;
+select json_array_elements_text('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]');
+select * from json_array_elements_text('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false,"stringy"]') q;
 
 -- populate_record
 create type jpop as (a text, b int, c timestamp);