Add array_to_json and row_to_json functions.

Also move the escape_json function from explain.c to json.c where it
seems to belong.

Andrew Dunstan, Reviewd by Abhijit Menon-Sen.

7 files changed, 579 insertions, 48 deletions

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index ec140040843..22adcb8c5a0 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -9617,6 +9617,65 @@ table2-mapping
   </sect2>
  </sect1>
 
+ <sect1 id="functions-json">
+  <title>JSON functions</title>
+
+  <indexterm zone="datatype-json">
+	<primary>JSON</primary>
+	<secondary>Functions and operators</secondary>
+  </indexterm>
+
+  <para>
+    This section descripbes the functions that are available for creating
+    JSON (see <xref linkend="datatype-json">) data.
+  </para>
+
+  <table id="functions-json-table">
+    <title>JSON Support Functions</title>
+    <tgroup cols="4">
+     <thead>
+      <row>
+       <entry>Function</entry>
+       <entry>Description</entry>
+       <entry>Example</entry>
+       <entry>Example Result</entry>
+      </row>
+     </thead>
+     <tbody>
+      <row>
+       <entry>
+         <indexterm>
+          <primary>array_to_json</primary>
+         </indexterm>
+         <literal>array_to_json(anyarray [, pretty_bool])</literal>
+       </entry>
+       <entry>
+         Returns the array as JSON. A Postgres multi-dimensional array 
+         becomes a JSON array of arrays. Line feeds will be added between 
+         dimension 1 elements if pretty_bool is true.
+       </entry>
+       <entry><literal>array_to_json('{{1,5},{99,100}}'::int[])</literal></entry>
+       <entry><literal>[[1,5],[99,100]]</literal></entry>
+      </row>
+      <row>
+       <entry>
+         <indexterm>
+          <primary>row_to_json</primary>
+         </indexterm>
+         <literal>row_to_json(record [, pretty_bool])</literal>
+       </entry>
+       <entry>
+         Returns the row as JSON. Line feeds will be added between level 
+         1 elements if pretty_bool is true.
+       </entry>
+       <entry><literal>row_to_json(row(1,'foo'))</literal></entry>
+       <entry><literal>{"f1":1,"f2":"foo"}</literal></entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </table>
+
+ </sect1>
 
  <sect1 id="functions-sequence">
   <title>Sequence Manipulation Functions</title>
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index e35ac590301..e57580e8add 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -24,6 +24,7 @@
 #include "rewrite/rewriteHandler.h"
 #include "tcop/tcopprot.h"
 #include "utils/builtins.h"
+#include "utils/json.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 #include "utils/snapmgr.h"
@@ -99,7 +100,6 @@ static void ExplainDummyGroup(const char *objtype, const char *labelname,
 static void ExplainXMLTag(const char *tagname, int flags, ExplainState *es);
 static void ExplainJSONLineEnding(ExplainState *es);
 static void ExplainYAMLLineStarting(ExplainState *es);
-static void escape_json(StringInfo buf, const char *str);
 static void escape_yaml(StringInfo buf, const char *str);
 
 
@@ -2319,51 +2319,6 @@ ExplainYAMLLineStarting(ExplainState *es)
 }
 
 /*
- * Produce a JSON string literal, properly escaping characters in the text.
- */
-static void
-escape_json(StringInfo buf, const char *str)
-{
-	const char *p;
-
-	appendStringInfoCharMacro(buf, '\"');
-	for (p = str; *p; p++)
-	{
-		switch (*p)
-		{
-			case '\b':
-				appendStringInfoString(buf, "\\b");
-				break;
-			case '\f':
-				appendStringInfoString(buf, "\\f");
-				break;
-			case '\n':
-				appendStringInfoString(buf, "\\n");
-				break;
-			case '\r':
-				appendStringInfoString(buf, "\\r");
-				break;
-			case '\t':
-				appendStringInfoString(buf, "\\t");
-				break;
-			case '"':
-				appendStringInfoString(buf, "\\\"");
-				break;
-			case '\\':
-				appendStringInfoString(buf, "\\\\");
-				break;
-			default:
-				if ((unsigned char) *p < ' ')
-					appendStringInfo(buf, "\\u%04x", (int) *p);
-				else
-					appendStringInfoCharMacro(buf, *p);
-				break;
-		}
-	}
-	appendStringInfoCharMacro(buf, '\"');
-}
-
-/*
  * YAML is a superset of JSON; unfortuantely, the YAML quoting rules are
  * ridiculously complicated -- as documented in sections 5.3 and 7.3.3 of
  * http://yaml.org/spec/1.2/spec.html -- so we chose to just quote everything.
diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index cbb81d1bf37..60addf2871f 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -13,11 +13,17 @@
  */
 #include "postgres.h"
 
+#include "catalog/pg_type.h"
+#include "executor/spi.h"
 #include "lib/stringinfo.h"
 #include "libpq/pqformat.h"
 #include "mb/pg_wchar.h"
+#include "parser/parse_coerce.h"
+#include "utils/array.h"
 #include "utils/builtins.h"
+#include "utils/lsyscache.h"
 #include "utils/json.h"
+#include "utils/typcache.h"
 
 typedef enum
 {
@@ -72,8 +78,11 @@ static void json_lex_number(JsonLexContext *lex, char *s);
 static void report_parse_error(JsonParseStack *stack, JsonLexContext *lex);
 static void report_invalid_token(JsonLexContext *lex);
 static char *extract_mb_char(char *s);
-
-extern Datum json_in(PG_FUNCTION_ARGS);
+static void composite_to_json(Datum composite, StringInfo result, bool use_line_feeds);
+static void array_dim_to_json(StringInfo result, int dim, int ndims,int * dims,
+							  Datum *vals, int * valcount, TYPCATEGORY tcategory,
+							  Oid typoutputfunc, bool use_line_feeds);
+static void array_to_json_internal(Datum array, StringInfo result, bool use_line_feeds);
 
 /*
  * Input.
@@ -663,3 +672,344 @@ extract_mb_char(char *s)
 
 	return res;
 }
+
+/*
+ * Turn a scalar Datum into JSON. Hand off a non-scalar datum to
+ * composite_to_json or array_to_json_internal as appropriate.
+ */
+static inline void
+datum_to_json(Datum val, StringInfo result, TYPCATEGORY tcategory,
+			  Oid typoutputfunc)
+{
+
+	char *outputstr;
+
+	if (val == (Datum) NULL)
+	{
+		appendStringInfoString(result,"null");
+		return;
+	}
+
+	switch (tcategory)
+	{
+		case TYPCATEGORY_ARRAY:
+			array_to_json_internal(val, result, false);
+			break;
+		case TYPCATEGORY_COMPOSITE:
+			composite_to_json(val, result, false);
+			break;
+		case TYPCATEGORY_BOOLEAN:
+			if (DatumGetBool(val))
+				appendStringInfoString(result,"true");
+			else
+				appendStringInfoString(result,"false");
+			break;
+		case TYPCATEGORY_NUMERIC:
+			outputstr = OidOutputFunctionCall(typoutputfunc, val);
+			/*
+			 * Don't call escape_json here. Numeric output should
+			 * be a valid JSON number and JSON numbers shouldn't
+			 * be quoted.
+			 */
+			appendStringInfoString(result, outputstr);
+			pfree(outputstr);
+			break;
+		default:
+			outputstr = OidOutputFunctionCall(typoutputfunc, val);
+			escape_json(result, outputstr);
+			pfree(outputstr);
+	}
+}
+
+/*
+ * Process a single dimension of an array.
+ * If it's the innermost dimension, output the values, otherwise call
+ * ourselves recursively to process the next dimension.
+ */
+static void
+array_dim_to_json(StringInfo result, int dim, int ndims,int * dims, Datum *vals,
+				  int * valcount, TYPCATEGORY tcategory, Oid typoutputfunc,
+				  bool use_line_feeds)
+{
+
+	int i;
+	char *sep;
+
+	Assert(dim < ndims);
+
+	sep = use_line_feeds ? ",\n " : ",";
+
+	appendStringInfoChar(result, '[');
+
+	for (i = 1; i <= dims[dim]; i++)
+	{
+		if (i > 1)
+			appendStringInfoString(result,sep);
+
+		if (dim + 1 == ndims)
+		{
+			datum_to_json(vals[*valcount],result,tcategory,typoutputfunc);
+			(*valcount)++;
+		}
+		else
+		{
+			/*
+			 * Do we want line feeds on inner dimensions of arrays?
+			 * For now we'll say no.
+			 */
+			array_dim_to_json(result, dim+1, ndims, dims, vals, valcount,
+							  tcategory,typoutputfunc,false);
+		}
+	}
+
+	appendStringInfoChar(result, ']');
+}
+
+/*
+ * Turn an array into JSON.
+ */
+static void
+array_to_json_internal(Datum array, StringInfo result, bool use_line_feeds)
+{
+	ArrayType  *v = DatumGetArrayTypeP(array);
+	Oid			element_type = ARR_ELEMTYPE(v);
+	int		   *dim;
+	int			ndim;
+	int			nitems;
+	int         count = 0;
+	Datum	   *elements;
+	bool       *nulls;
+
+	int16		typlen;
+	bool		typbyval;
+	char		typalign,
+				typdelim;
+	Oid			typioparam;
+	Oid			typoutputfunc;
+	TYPCATEGORY tcategory;
+
+	ndim = ARR_NDIM(v);
+	dim = ARR_DIMS(v);
+	nitems = ArrayGetNItems(ndim, dim);
+
+	if (nitems <= 0)
+	{
+		appendStringInfoString(result,"[]");
+		return;
+	}
+
+	get_type_io_data(element_type, IOFunc_output,
+					 &typlen, &typbyval, &typalign,
+					 &typdelim, &typioparam, &typoutputfunc);
+
+	deconstruct_array(v, element_type, typlen, typbyval,
+					  typalign, &elements, &nulls,
+					  &nitems);
+
+	/* can't have an array of arrays, so this is the only special case here */
+	if (element_type == RECORDOID)
+		tcategory = TYPCATEGORY_COMPOSITE;
+	else
+		tcategory = TypeCategory(element_type);
+
+	array_dim_to_json(result, 0, ndim, dim, elements, &count, tcategory,
+					  typoutputfunc, use_line_feeds);
+
+	pfree(elements);
+	pfree(nulls);
+}
+
+/*
+ * Turn a composite / record into JSON.
+ */
+static void
+composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
+{
+    HeapTupleHeader td;
+    Oid         tupType;
+    int32       tupTypmod;
+    TupleDesc   tupdesc;
+    HeapTupleData tmptup, *tuple;
+	int         i;
+	bool        needsep = false;
+	char       *sep;
+
+	sep = use_line_feeds ? ",\n " : ",";
+
+    td = DatumGetHeapTupleHeader(composite);
+
+    /* Extract rowtype info and find a tupdesc */
+    tupType = HeapTupleHeaderGetTypeId(td);
+    tupTypmod = HeapTupleHeaderGetTypMod(td);
+    tupdesc = lookup_rowtype_tupdesc(tupType, tupTypmod);
+
+    /* Build a temporary HeapTuple control structure */
+    tmptup.t_len = HeapTupleHeaderGetDatumLength(td);
+    tmptup.t_data = td;
+	tuple = &tmptup;
+
+	appendStringInfoChar(result,'{');
+
+    for (i = 0; i < tupdesc->natts; i++)
+    {
+        Datum       val, origval;
+        bool        isnull;
+        char       *attname;
+		TYPCATEGORY tcategory;
+		Oid			typoutput;
+		bool		typisvarlena;
+
+		if (tupdesc->attrs[i]->attisdropped)
+            continue;
+
+		if (needsep)
+			appendStringInfoString(result,sep);
+		needsep = true;
+
+        attname = NameStr(tupdesc->attrs[i]->attname);
+		escape_json(result,attname);
+		appendStringInfoChar(result,':');
+
+        origval = heap_getattr(tuple, i + 1, tupdesc, &isnull);
+
+		if (tupdesc->attrs[i]->atttypid == RECORDARRAYOID)
+			tcategory = TYPCATEGORY_ARRAY;
+		else if (tupdesc->attrs[i]->atttypid == RECORDOID)
+			tcategory = TYPCATEGORY_COMPOSITE;
+		else
+			tcategory = TypeCategory(tupdesc->attrs[i]->atttypid);
+
+		getTypeOutputInfo(tupdesc->attrs[i]->atttypid,
+						  &typoutput, &typisvarlena);
+
+		/*
+		 * If we have a toasted datum, forcibly detoast it here to avoid memory
+		 * leakage inside the type's output routine.
+		 */
+		if (typisvarlena && ! isnull)
+			val = PointerGetDatum(PG_DETOAST_DATUM(origval));
+		else
+			val = origval;
+
+		datum_to_json(val, result, tcategory, typoutput);
+
+		/* Clean up detoasted copy, if any */
+		if (val != origval)
+			pfree(DatumGetPointer(val));
+	}
+
+	appendStringInfoChar(result,'}');
+    ReleaseTupleDesc(tupdesc);
+}
+
+/*
+ * SQL function array_to_json(row)
+ */
+extern Datum
+array_to_json(PG_FUNCTION_ARGS)
+{
+	Datum    array = PG_GETARG_DATUM(0);
+	StringInfo	result;
+
+	result = makeStringInfo();
+
+	array_to_json_internal(array, result, false);
+
+	PG_RETURN_TEXT_P(cstring_to_text(result->data));
+};
+
+/*
+ * SQL function array_to_json(row, prettybool)
+ */
+extern Datum
+array_to_json_pretty(PG_FUNCTION_ARGS)
+{
+	Datum    array = PG_GETARG_DATUM(0);
+	bool     use_line_feeds = PG_GETARG_BOOL(1);
+	StringInfo	result;
+
+	result = makeStringInfo();
+
+	array_to_json_internal(array, result, use_line_feeds);
+
+	PG_RETURN_TEXT_P(cstring_to_text(result->data));
+};
+
+/*
+ * SQL function row_to_json(row)
+ */
+extern Datum
+row_to_json(PG_FUNCTION_ARGS)
+{
+	Datum    array = PG_GETARG_DATUM(0);
+	StringInfo	result;
+
+	result = makeStringInfo();
+
+	composite_to_json(array, result, false);
+
+	PG_RETURN_TEXT_P(cstring_to_text(result->data));
+};
+
+/*
+ * SQL function row_to_json(row, prettybool)
+ */
+extern Datum
+row_to_json_pretty(PG_FUNCTION_ARGS)
+{
+	Datum    array = PG_GETARG_DATUM(0);
+	bool     use_line_feeds = PG_GETARG_BOOL(1);
+	StringInfo	result;
+
+	result = makeStringInfo();
+
+	composite_to_json(array, result, use_line_feeds);
+
+	PG_RETURN_TEXT_P(cstring_to_text(result->data));
+};
+
+/*
+ * Produce a JSON string literal, properly escaping characters in the text.
+ */
+void
+escape_json(StringInfo buf, const char *str)
+{
+	const char *p;
+
+	appendStringInfoCharMacro(buf, '\"');
+	for (p = str; *p; p++)
+	{
+		switch (*p)
+		{
+			case '\b':
+				appendStringInfoString(buf, "\\b");
+				break;
+			case '\f':
+				appendStringInfoString(buf, "\\f");
+				break;
+			case '\n':
+				appendStringInfoString(buf, "\\n");
+				break;
+			case '\r':
+				appendStringInfoString(buf, "\\r");
+				break;
+			case '\t':
+				appendStringInfoString(buf, "\\t");
+				break;
+			case '"':
+				appendStringInfoString(buf, "\\\"");
+				break;
+			case '\\':
+				appendStringInfoString(buf, "\\\\");
+				break;
+			default:
+				if ((unsigned char) *p < ' ')
+					appendStringInfo(buf, "\\u%04x", (int) *p);
+				else
+					appendStringInfoCharMacro(buf, *p);
+				break;
+		}
+	}
+	appendStringInfoCharMacro(buf, '\"');
+}
+
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 5dc6d05478f..8fc4ddb4b56 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4031,6 +4031,14 @@ DATA(insert OID = 323 (  json_recv		   PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 11
 DESCR("I/O");
 DATA(insert OID = 324 (  json_send		   PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 17 "114" _null_ _null_ _null_ _null_ json_send _null_ _null_ _null_ ));
 DESCR("I/O");
+DATA(insert OID = 3153 (  array_to_json	   PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 114 "2277" _null_ _null_ _null_ _null_ array_to_json _null_ _null_ _null_ ));
+DESCR("map array to json");
+DATA(insert OID = 3154 (  array_to_json	   PGNSP PGUID 12 1 0 0 0 f f f t f s 2 0 114 "2277 16" _null_ _null_ _null_ _null_ array_to_json_pretty _null_ _null_ _null_ ));
+DESCR("map array to json with optional pretty printing");
+DATA(insert OID = 3155 (  row_to_json	   PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 114 "2249" _null_ _null_ _null_ _null_ row_to_json _null_ _null_ _null_ ));
+DESCR("map row to json");
+DATA(insert OID = 3156 (  row_to_json	   PGNSP PGUID 12 1 0 0 0 f f f t f s 2 0 114 "2249 16" _null_ _null_ _null_ _null_ row_to_json_pretty _null_ _null_ _null_ ));
+DESCR("map row to json with optional pretty printing");
 
 /* uuid */
 DATA(insert OID = 2952 (  uuid_in		   PGNSP PGUID 12 1 0 0 0 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 ee87fd61d7c..415787b458d 100644
--- a/src/include/utils/json.h
+++ b/src/include/utils/json.h
@@ -20,5 +20,10 @@ extern Datum json_in(PG_FUNCTION_ARGS);
 extern Datum json_out(PG_FUNCTION_ARGS);
 extern Datum json_recv(PG_FUNCTION_ARGS);
 extern Datum json_send(PG_FUNCTION_ARGS);
+extern Datum array_to_json(PG_FUNCTION_ARGS);
+extern Datum array_to_json_pretty(PG_FUNCTION_ARGS);
+extern Datum row_to_json(PG_FUNCTION_ARGS);
+extern Datum row_to_json_pretty(PG_FUNCTION_ARGS);
+extern void  escape_json(StringInfo buf, const char *str);
 
 #endif   /* XML_H */
diff --git a/src/test/regress/expected/json.out b/src/test/regress/expected/json.out
index 5ef65f7c972..f2148bf362f 100644
--- a/src/test/regress/expected/json.out
+++ b/src/test/regress/expected/json.out
@@ -256,3 +256,114 @@ ERROR:  invalid input syntax for type json: "    "
 LINE 1: SELECT '    '::json;
                ^
 DETAIL:  The input string ended unexpectedly.
+--constructors
+-- array_to_json
+SELECT array_to_json(array(select 1 as a));
+ array_to_json 
+---------------
+ [1]
+(1 row)
+
+SELECT array_to_json(array_agg(q),false) from (select x as b, x * 2 as c from generate_series(1,3) x) q;
+                   array_to_json                   
+---------------------------------------------------
+ [{"f1":1,"f2":2},{"f1":2,"f2":4},{"f1":3,"f2":6}]
+(1 row)
+
+SELECT array_to_json(array_agg(q),true) from (select x as b, x * 2 as c from generate_series(1,3) x) q;
+   array_to_json   
+-------------------
+ [{"f1":1,"f2":2},+
+  {"f1":2,"f2":4},+
+  {"f1":3,"f2":6}]
+(1 row)
+
+SELECT array_to_json(array_agg(q),false)
+  FROM ( SELECT $$a$$ || x AS b, y AS c, 
+               ARRAY[ROW(x.*,ARRAY[1,2,3]),
+               ROW(y.*,ARRAY[4,5,6])] AS z 
+         FROM generate_series(1,2) x, 
+              generate_series(4,5) y) q;
+                                                                                                                                 array_to_json                                                                                                                                 
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ [{"b":"a1","c":4,"z":[{"f1":1,"f2":[1,2,3]},{"f1":4,"f2":[4,5,6]}]},{"b":"a1","c":5,"z":[{"f1":1,"f2":[1,2,3]},{"f1":5,"f2":[4,5,6]}]},{"b":"a2","c":4,"z":[{"f1":2,"f2":[1,2,3]},{"f1":4,"f2":[4,5,6]}]},{"b":"a2","c":5,"z":[{"f1":2,"f2":[1,2,3]},{"f1":5,"f2":[4,5,6]}]}]
+(1 row)
+
+SELECT array_to_json(array_agg(x),false) from generate_series(5,10) x;
+ array_to_json  
+----------------
+ [5,6,7,8,9,10]
+(1 row)
+
+SELECT array_to_json('{{1,5},{99,100}}'::int[]);
+  array_to_json   
+------------------
+ [[1,5],[99,100]]
+(1 row)
+
+-- row_to_json
+SELECT row_to_json(row(1,'foo'));
+     row_to_json     
+---------------------
+ {"f1":1,"f2":"foo"}
+(1 row)
+
+SELECT row_to_json(q) 
+FROM (SELECT $$a$$ || x AS b, 
+         y AS c, 
+         ARRAY[ROW(x.*,ARRAY[1,2,3]),
+               ROW(y.*,ARRAY[4,5,6])] AS z 
+      FROM generate_series(1,2) x, 
+           generate_series(4,5) y) q;
+                            row_to_json                             
+--------------------------------------------------------------------
+ {"b":"a1","c":4,"z":[{"f1":1,"f2":[1,2,3]},{"f1":4,"f2":[4,5,6]}]}
+ {"b":"a1","c":5,"z":[{"f1":1,"f2":[1,2,3]},{"f1":5,"f2":[4,5,6]}]}
+ {"b":"a2","c":4,"z":[{"f1":2,"f2":[1,2,3]},{"f1":4,"f2":[4,5,6]}]}
+ {"b":"a2","c":5,"z":[{"f1":2,"f2":[1,2,3]},{"f1":5,"f2":[4,5,6]}]}
+(4 rows)
+
+SELECT row_to_json(q,true) 
+FROM (SELECT $$a$$ || x AS b, 
+         y AS c, 
+         ARRAY[ROW(x.*,ARRAY[1,2,3]),
+               ROW(y.*,ARRAY[4,5,6])] AS z 
+      FROM generate_series(1,2) x, 
+           generate_series(4,5) y) q;
+                     row_to_json                     
+-----------------------------------------------------
+ {"b":"a1",                                         +
+  "c":4,                                            +
+  "z":[{"f1":1,"f2":[1,2,3]},{"f1":4,"f2":[4,5,6]}]}
+ {"b":"a1",                                         +
+  "c":5,                                            +
+  "z":[{"f1":1,"f2":[1,2,3]},{"f1":5,"f2":[4,5,6]}]}
+ {"b":"a2",                                         +
+  "c":4,                                            +
+  "z":[{"f1":2,"f2":[1,2,3]},{"f1":4,"f2":[4,5,6]}]}
+ {"b":"a2",                                         +
+  "c":5,                                            +
+  "z":[{"f1":2,"f2":[1,2,3]},{"f1":5,"f2":[4,5,6]}]}
+(4 rows)
+
+CREATE TEMP TABLE rows AS
+SELECT x, 'txt' || x as y
+FROM generate_series(1,3) AS x;
+SELECT row_to_json(q,true) 
+FROM rows q;
+ row_to_json  
+--------------
+ {"x":1,     +
+  "y":"txt1"}
+ {"x":2,     +
+  "y":"txt2"}
+ {"x":3,     +
+  "y":"txt3"}
+(3 rows)
+
+SELECT row_to_json(row((select array_agg(x) as d from generate_series(5,10) x)),false);
+      row_to_json      
+-----------------------
+ {"f1":[5,6,7,8,9,10]}
+(1 row)
+
diff --git a/src/test/regress/sql/json.sql b/src/test/regress/sql/json.sql
index 440398b9b9f..61273555aae 100644
--- a/src/test/regress/sql/json.sql
+++ b/src/test/regress/sql/json.sql
@@ -54,3 +54,46 @@ SELECT 'truf'::json;			-- ERROR, not a keyword
 SELECT 'trues'::json;			-- ERROR, not a keyword
 SELECT ''::json;				-- ERROR, no value
 SELECT '    '::json;			-- ERROR, no value
+
+--constructors
+-- array_to_json
+
+SELECT array_to_json(array(select 1 as a));
+SELECT array_to_json(array_agg(q),false) from (select x as b, x * 2 as c from generate_series(1,3) x) q;
+SELECT array_to_json(array_agg(q),true) from (select x as b, x * 2 as c from generate_series(1,3) x) q;
+SELECT array_to_json(array_agg(q),false)
+  FROM ( SELECT $$a$$ || x AS b, y AS c, 
+               ARRAY[ROW(x.*,ARRAY[1,2,3]),
+               ROW(y.*,ARRAY[4,5,6])] AS z 
+         FROM generate_series(1,2) x, 
+              generate_series(4,5) y) q;
+SELECT array_to_json(array_agg(x),false) from generate_series(5,10) x;
+SELECT array_to_json('{{1,5},{99,100}}'::int[]);
+
+-- row_to_json
+SELECT row_to_json(row(1,'foo'));
+
+SELECT row_to_json(q) 
+FROM (SELECT $$a$$ || x AS b, 
+         y AS c, 
+         ARRAY[ROW(x.*,ARRAY[1,2,3]),
+               ROW(y.*,ARRAY[4,5,6])] AS z 
+      FROM generate_series(1,2) x, 
+           generate_series(4,5) y) q;
+
+SELECT row_to_json(q,true) 
+FROM (SELECT $$a$$ || x AS b, 
+         y AS c, 
+         ARRAY[ROW(x.*,ARRAY[1,2,3]),
+               ROW(y.*,ARRAY[4,5,6])] AS z 
+      FROM generate_series(1,2) x, 
+           generate_series(4,5) y) q;
+
+CREATE TEMP TABLE rows AS
+SELECT x, 'txt' || x as y
+FROM generate_series(1,3) AS x;
+
+SELECT row_to_json(q,true) 
+FROM rows q;
+
+SELECT row_to_json(row((select array_agg(x) as d from generate_series(5,10) x)),false);