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Add 'ignore_nulls' option to row_to_json
Provide an option to skip NULL values in a row when generating a JSON object from that row with row_to_json. This can reduce the size of the JSON object in cases where columns are NULL without really reducing the information in the JSON object. This also makes row_to_json into a single function with default values, rather than having multiple functions. In passing, change array_to_json to also be a single function with default values (we don't add an 'ignore_nulls' option yet- it's not clear that there is a sensible use-case there, and it hasn't been asked for in any case). Pavel Stehule
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8 files changed

+118
-51
lines changed

8 files changed

+118
-51
lines changed

‎doc/src/sgml/func.sgml‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -10309,11 +10309,13 @@ table2-mapping
1030910309
</row>
1031010310
<row>
1031110311
<entry>
10312-
<literal>row_to_json(record [, pretty_bool])</literal>
10312+
<literal>row_to_json(rowval record [, pretty bool [, ignore_nulls bool] ])</literal>
1031310313
</entry>
1031410314
<entry>
1031510315
Returns the row as a JSON object. Line feeds will be added between
10316-
level-1 elements if <parameter>pretty_bool</parameter> is true.
10316+
level-1 elements if <parameter>pretty_bool</parameter> is true. Elements
10317+
with NULL values will be skipped when <parameter>ignore_nulls</parameter>
10318+
is true.
1031710319
</entry>
1031810320
<entry><literal>row_to_json(row(1,'foo'))</literal></entry>
1031910321
<entry><literal>{"f1":1,"f2":"foo"}</literal></entry>

‎src/backend/catalog/system_views.sql‎

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -867,3 +867,17 @@ RETURNS interval
867867
LANGUAGE INTERNAL
868868
STRICT IMMUTABLE
869869
AS 'make_interval';
870+
871+
CREATE OR REPLACE FUNCTION
872+
row_to_json(rowval record, pretty boolean DEFAULT false, ignore_nulls boolean DEFAULT false)
873+
RETURNS json
874+
LANGUAGE INTERNAL
875+
STRICT STABLE
876+
AS 'row_to_json';
877+
878+
CREATE OR REPLACE FUNCTION
879+
array_to_json(arrayval anyarray, pretty boolean DEFAULT false)
880+
RETURNS json
881+
LANGUAGE INTERNAL
882+
STRICT STABLE
883+
AS 'array_to_json';

‎src/backend/utils/adt/json.c‎

Lines changed: 15 additions & 40 deletions
Original file line numberDiff line numberDiff line change
@@ -79,7 +79,8 @@ static void report_invalid_token(JsonLexContext *lex);
7979
static int report_json_context(JsonLexContext *lex);
8080
static char *extract_mb_char(char *s);
8181
static void composite_to_json(Datum composite, StringInfo result,
82-
bool use_line_feeds);
82+
bool use_line_feeds,
83+
bool ignore_nulls);
8384
static void array_dim_to_json(StringInfo result, int dim, int ndims, int *dims,
8485
Datum *vals, bool *nulls, int *valcount,
8586
JsonTypeCategory tcategory, Oid outfuncoid,
@@ -1362,7 +1363,7 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
13621363
array_to_json_internal(val, result, false);
13631364
break;
13641365
case JSONTYPE_COMPOSITE:
1365-
composite_to_json(val, result, false);
1366+
composite_to_json(val, result, false, false);
13661367
break;
13671368
case JSONTYPE_BOOL:
13681369
outputstr = DatumGetBool(val) ? "true" : "false";
@@ -1591,7 +1592,8 @@ array_to_json_internal(Datum array, StringInfo result, bool use_line_feeds)
15911592
* Turn a composite / record into JSON.
15921593
*/
15931594
static void
1594-
composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
1595+
composite_to_json(Datum composite, StringInfo result, bool use_line_feeds,
1596+
bool ignore_nulls)
15951597
{
15961598
HeapTupleHeader td;
15971599
Oid tupType;
@@ -1630,6 +1632,12 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
16301632
if (tupdesc->attrs[i]->attisdropped)
16311633
continue;
16321634

1635+
val = heap_getattr(tuple, i + 1, tupdesc, &isnull);
1636+
1637+
/* Don't serialize NULL field when we don't want it */
1638+
if (isnull && ignore_nulls)
1639+
continue;
1640+
16331641
if (needsep)
16341642
appendStringInfoString(result, sep);
16351643
needsep = true;
@@ -1638,8 +1646,6 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
16381646
escape_json(result, attname);
16391647
appendStringInfoChar(result, ':');
16401648

1641-
val = heap_getattr(tuple, i + 1, tupdesc, &isnull);
1642-
16431649
if (isnull)
16441650
{
16451651
tcategory = JSONTYPE_NULL;
@@ -1687,27 +1693,11 @@ add_json(Datum val, bool is_null, StringInfo result,
16871693
datum_to_json(val, is_null, result, tcategory, outfuncoid, key_scalar);
16881694
}
16891695

1690-
/*
1691-
* SQL function array_to_json(row)
1692-
*/
1693-
extern Datum
1694-
array_to_json(PG_FUNCTION_ARGS)
1695-
{
1696-
Datum array = PG_GETARG_DATUM(0);
1697-
StringInfo result;
1698-
1699-
result = makeStringInfo();
1700-
1701-
array_to_json_internal(array, result, false);
1702-
1703-
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
1704-
}
1705-
17061696
/*
17071697
* SQL function array_to_json(row, prettybool)
17081698
*/
17091699
extern Datum
1710-
array_to_json_pretty(PG_FUNCTION_ARGS)
1700+
array_to_json(PG_FUNCTION_ARGS)
17111701
{
17121702
Datum array = PG_GETARG_DATUM(0);
17131703
bool use_line_feeds = PG_GETARG_BOOL(1);
@@ -1721,34 +1711,19 @@ array_to_json_pretty(PG_FUNCTION_ARGS)
17211711
}
17221712

17231713
/*
1724-
* SQL function row_to_json(row)
1714+
* SQL function row_to_json(rowval record, pretty bool, ignore_nulls bool)
17251715
*/
17261716
extern Datum
17271717
row_to_json(PG_FUNCTION_ARGS)
1728-
{
1729-
Datum array = PG_GETARG_DATUM(0);
1730-
StringInfo result;
1731-
1732-
result = makeStringInfo();
1733-
1734-
composite_to_json(array, result, false);
1735-
1736-
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
1737-
}
1738-
1739-
/*
1740-
* SQL function row_to_json(row, prettybool)
1741-
*/
1742-
extern Datum
1743-
row_to_json_pretty(PG_FUNCTION_ARGS)
17441718
{
17451719
Datum array = PG_GETARG_DATUM(0);
17461720
bool use_line_feeds = PG_GETARG_BOOL(1);
1721+
bool ignore_nulls = PG_GETARG_BOOL(2);
17471722
StringInfo result;
17481723

17491724
result = makeStringInfo();
17501725

1751-
composite_to_json(array, result, use_line_feeds);
1726+
composite_to_json(array, result, use_line_feeds, ignore_nulls);
17521727

17531728
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
17541729
}

‎src/include/catalog/catversion.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,6 @@
5353
*/
5454

5555
/* yyyymmddN */
56-
#define CATALOG_VERSION_NO 201409101
56+
#define CATALOG_VERSION_NO 201409111
5757

5858
#endif

‎src/include/catalog/pg_proc.h‎

Lines changed: 2 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -4203,14 +4203,10 @@ DATA(insert OID = 323 ( json_recv PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0
42034203
DESCR("I/O");
42044204
DATA(insert OID = 324 ( json_send PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 17 "114" _null_ _null_ _null_ _null_ json_send _null_ _null_ _null_ ));
42054205
DESCR("I/O");
4206-
DATA(insert OID = 3153 ( array_to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 114 "2277" _null_ _null_ _null_ _null_ array_to_json _null_ _null_ _null_ ));
4206+
DATA(insert OID = 3153 ( array_to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 114 "2277 16" _null_ _null_ "{arrayval,pretty}" _null_ array_to_json _null_ _null_ _null_ ));
42074207
DESCR("map array to json");
4208-
DATA(insert OID = 3154 ( array_to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 114 "2277 16" _null_ _null_ _null_ _null_ array_to_json_pretty _null_ _null_ _null_ ));
4209-
DESCR("map array to json with optional pretty printing");
4210-
DATA(insert OID = 3155 ( row_to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 114 "2249" _null_ _null_ _null_ _null_ row_to_json _null_ _null_ _null_ ));
4208+
DATA(insert OID = 3155 ( row_to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 3 0 114 "2249 16 16" _null_ _null_ "{rowval,pretty,ignore_nulls}" _null_ row_to_json _null_ _null_ _null_ ));
42114209
DESCR("map row to json");
4212-
DATA(insert OID = 3156 ( row_to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 114 "2249 16" _null_ _null_ _null_ _null_ row_to_json_pretty _null_ _null_ _null_ ));
4213-
DESCR("map row to json with optional pretty printing");
42144210
DATA(insert OID = 3173 ( json_agg_transfn PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2283" _null_ _null_ _null_ _null_ json_agg_transfn _null_ _null_ _null_ ));
42154211
DESCR("json aggregate transition function");
42164212
DATA(insert OID = 3174 ( json_agg_finalfn PGNSP PGUID 12 1 0 0 0 f f f f f f i 1 0 114 "2281" _null_ _null_ _null_ _null_ json_agg_finalfn _null_ _null_ _null_ ));

‎src/include/utils/json.h‎

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -23,9 +23,7 @@ extern Datum json_out(PG_FUNCTION_ARGS);
2323
extern Datum json_recv(PG_FUNCTION_ARGS);
2424
extern Datum json_send(PG_FUNCTION_ARGS);
2525
extern Datum array_to_json(PG_FUNCTION_ARGS);
26-
extern Datum array_to_json_pretty(PG_FUNCTION_ARGS);
2726
extern Datum row_to_json(PG_FUNCTION_ARGS);
28-
extern Datum row_to_json_pretty(PG_FUNCTION_ARGS);
2927
extern Datum to_json(PG_FUNCTION_ARGS);
3028

3129
extern Datum json_agg_transfn(PG_FUNCTION_ARGS);

‎src/test/regress/expected/json.out‎

Lines changed: 58 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -397,12 +397,70 @@ FROM rows q;
397397
"y":"txt3"}
398398
(3 rows)
399399

400+
SELECT row_to_json(q,pretty := true)
401+
FROM rows q;
402+
row_to_json
403+
--------------
404+
{"x":1, +
405+
"y":"txt1"}
406+
{"x":2, +
407+
"y":"txt2"}
408+
{"x":3, +
409+
"y":"txt3"}
410+
(3 rows)
411+
400412
SELECT row_to_json(row((select array_agg(x) as d from generate_series(5,10) x)),false);
401413
row_to_json
402414
-----------------------
403415
{"f1":[5,6,7,8,9,10]}
404416
(1 row)
405417

418+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
419+
(10,NULL, NULL),
420+
(NULL, NULL, NULL)) g(a,b,c))
421+
SELECT row_to_json(x, false, false) FROM x;
422+
row_to_json
423+
------------------------------
424+
{"a":10,"b":20,"c":30}
425+
{"a":10,"b":null,"c":null}
426+
{"a":null,"b":null,"c":null}
427+
(3 rows)
428+
429+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
430+
(10,NULL, NULL),
431+
(NULL, NULL, NULL)) g(a,b,c))
432+
SELECT row_to_json(x, false, true) FROM x;
433+
row_to_json
434+
------------------------
435+
{"a":10,"b":20,"c":30}
436+
{"a":10}
437+
{}
438+
(3 rows)
439+
440+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
441+
(10,NULL, NULL),
442+
(NULL, NULL, NULL)) g(a,b,c))
443+
SELECT row_to_json(x, ignore_nulls := true) FROM x;
444+
row_to_json
445+
------------------------
446+
{"a":10,"b":20,"c":30}
447+
{"a":10}
448+
{}
449+
(3 rows)
450+
451+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
452+
(10,NULL, NULL),
453+
(NULL, NULL, NULL)) g(a,b,c))
454+
SELECT row_to_json(x, ignore_nulls := true, pretty := true) FROM x;
455+
row_to_json
456+
-------------
457+
{"a":10, +
458+
"b":20, +
459+
"c":30}
460+
{"a":10}
461+
{}
462+
(3 rows)
463+
406464
-- to_json, timestamps
407465
select to_json(timestamp '2014-05-28 12:22:35.614298');
408466
to_json

‎src/test/regress/sql/json.sql‎

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -98,8 +98,32 @@ FROM generate_series(1,3) AS x;
9898
SELECT row_to_json(q,true)
9999
FROM rows q;
100100

101+
SELECT row_to_json(q,pretty := true)
102+
FROM rows q;
103+
101104
SELECT row_to_json(row((select array_agg(x) as d from generate_series(5,10) x)),false);
102105

106+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
107+
(10,NULL, NULL),
108+
(NULL, NULL, NULL)) g(a,b,c))
109+
SELECT row_to_json(x, false, false) FROM x;
110+
111+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
112+
(10,NULL, NULL),
113+
(NULL, NULL, NULL)) g(a,b,c))
114+
SELECT row_to_json(x, false, true) FROM x;
115+
116+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
117+
(10,NULL, NULL),
118+
(NULL, NULL, NULL)) g(a,b,c))
119+
SELECT row_to_json(x, ignore_nulls := true) FROM x;
120+
121+
WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
122+
(10,NULL, NULL),
123+
(NULL, NULL, NULL)) g(a,b,c))
124+
SELECT row_to_json(x, ignore_nulls := true, pretty := true) FROM x;
125+
126+
103127
-- to_json, timestamps
104128

105129
select to_json(timestamp '2014-05-28 12:22:35.614298');

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