Hello
I am sending small patch, that allows ignore nulls in row_to_json function.
It allow significant size reduction of generated JSON documents.
Regards
Pavel
2014-05-25 7:53 GMT+02:00 Pavel Stehule <pavel.steh...@gmail.com>:
> Hello
>
> In Czech Postgres mailing list was user request for serialization to json
> without null values.
>
> He needs a similar behave like XMLFOREST has - it ignores NULLs
>
> In some situations and conversions, when your table is +/- sparse matrix,
> this request is valid
>
> postgres=# select hstore(omega) from omega;
> hstore
> ─────────────────────────────────
> "a"=>"10", "b"=>"20", "c"=>NULL
> "a"=>NULL, "b"=>"20", "c"=>"30"
> (2 rows)
>
> Proposed function
>
> postgres=# select hstore(omega, ignore_nulls := true) from omega;
> hstore
> ─────────────────────────────────
> "a"=>"10", "b"=>"20"
> "b"=>"20", "c"=>"30"
> (2 rows)
>
> What do you thinking about this proposal?
>
> Regards
>
> Pavel
>
>
commit c97bb5fd8b6c68a1141430d47964ebc3488f4429
Author: Pavel Stehule <pavel.steh...@gooddata.com>
Date: Sat Jun 28 17:40:47 2014 +0200
initial
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index f475458..d46b90d 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -10290,11 +10290,12 @@ table2-mapping
</row>
<row>
<entry>
- <literal>row_to_json(record [, pretty_bool])</literal>
+ <literal>row_to_json(record [, pretty_bool [, ignore_nulls] ])</literal>
</entry>
<entry>
Returns the row as a JSON object. Line feeds will be added between
- level-1 elements if <parameter>pretty_bool</parameter> is true.
+ level-1 elements if <parameter>pretty_bool</parameter> is true. Ignore
+ NULL when <parameter>ignore_nulls</parameter> is true.
</entry>
<entry><literal>row_to_json(row(1,'foo'))</literal></entry>
<entry><literal>{"f1":1,"f2":"foo"}</literal></entry>
diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 841dd1a..22e1dd6 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -77,7 +77,8 @@ static void report_invalid_token(JsonLexContext *lex);
static int report_json_context(JsonLexContext *lex);
static char *extract_mb_char(char *s);
static void composite_to_json(Datum composite, StringInfo result,
- bool use_line_feeds);
+ bool use_line_feeds,
+ bool ignore_nulls);
static void array_dim_to_json(StringInfo result, int dim, int ndims, int *dims,
Datum *vals, bool *nulls, int *valcount,
JsonTypeCategory tcategory, Oid outfuncoid,
@@ -1355,7 +1356,7 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
array_to_json_internal(val, result, false);
break;
case JSONTYPE_COMPOSITE:
- composite_to_json(val, result, false);
+ composite_to_json(val, result, false, false);
break;
case JSONTYPE_BOOL:
outputstr = DatumGetBool(val) ? "true" : "false";
@@ -1560,7 +1561,8 @@ array_to_json_internal(Datum array, StringInfo result, bool use_line_feeds)
* Turn a composite / record into JSON.
*/
static void
-composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
+composite_to_json(Datum composite, StringInfo result, bool use_line_feeds,
+ bool ignore_nulls)
{
HeapTupleHeader td;
Oid tupType;
@@ -1599,6 +1601,12 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
if (tupdesc->attrs[i]->attisdropped)
continue;
+ val = heap_getattr(tuple, i + 1, tupdesc, &isnull);
+
+ /* Don't serialize NULL field when we don't want it */
+ if (isnull && ignore_nulls)
+ continue;
+
if (needsep)
appendStringInfoString(result, sep);
needsep = true;
@@ -1607,8 +1615,6 @@ composite_to_json(Datum composite, StringInfo result, bool use_line_feeds)
escape_json(result, attname);
appendStringInfoChar(result, ':');
- val = heap_getattr(tuple, i + 1, tupdesc, &isnull);
-
if (isnull)
{
tcategory = JSONTYPE_NULL;
@@ -1700,7 +1706,7 @@ row_to_json(PG_FUNCTION_ARGS)
result = makeStringInfo();
- composite_to_json(array, result, false);
+ composite_to_json(array, result, false, false);
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
}
@@ -1717,7 +1723,25 @@ row_to_json_pretty(PG_FUNCTION_ARGS)
result = makeStringInfo();
- composite_to_json(array, result, use_line_feeds);
+ composite_to_json(array, result, use_line_feeds, false);
+
+ PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
+}
+
+/*
+ * SQL function row_to_json(row, prettybool, ignore_nulls)
+ */
+extern Datum
+row_to_json_pretty_choosy(PG_FUNCTION_ARGS)
+{
+ Datum array = PG_GETARG_DATUM(0);
+ bool use_line_feeds = PG_GETARG_BOOL(1);
+ bool ignore_nulls = PG_GETARG_BOOL(2);
+ StringInfo result;
+
+ result = makeStringInfo();
+
+ composite_to_json(array, result, use_line_feeds, ignore_nulls);
PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
}
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 762ce6c..ccd3db5 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4197,6 +4197,8 @@ DATA(insert OID = 3155 ( row_to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 1
DESCR("map row to json");
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_ ));
DESCR("map row to json with optional pretty printing");
+DATA(insert OID = 3255 ( 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_ _null_ _null_ row_to_json_pretty_choosy _null_ _null_ _null_ ));
+DESCR("map row to json with optional pretty printing and skipping NULLs");
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_ ));
DESCR("json aggregate transition function");
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_ ));
diff --git a/src/include/utils/json.h b/src/include/utils/json.h
index 82cc48b..6e43dec 100644
--- a/src/include/utils/json.h
+++ b/src/include/utils/json.h
@@ -26,6 +26,7 @@ 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 Datum row_to_json_pretty_choosy(PG_FUNCTION_ARGS);
extern Datum to_json(PG_FUNCTION_ARGS);
extern Datum json_agg_transfn(PG_FUNCTION_ARGS);
diff --git a/src/test/regress/expected/json.out b/src/test/regress/expected/json.out
index d1e32a1..cd4d8fc 100644
--- a/src/test/regress/expected/json.out
+++ b/src/test/regress/expected/json.out
@@ -403,6 +403,28 @@ SELECT row_to_json(row((select array_agg(x) as d from generate_series(5,10) x)),
{"f1":[5,6,7,8,9,10]}
(1 row)
+WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
+ (10,NULL, NULL),
+ (NULL, NULL, NULL)) g(a,b,c))
+ SELECT row_to_json(x, false, false) FROM x;
+ row_to_json
+------------------------------
+ {"a":10,"b":20,"c":30}
+ {"a":10,"b":null,"c":null}
+ {"a":null,"b":null,"c":null}
+(3 rows)
+
+WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
+ (10,NULL, NULL),
+ (NULL, NULL, NULL)) g(a,b,c))
+ SELECT row_to_json(x, false, true) FROM x;
+ row_to_json
+------------------------
+ {"a":10,"b":20,"c":30}
+ {"a":10}
+ {}
+(3 rows)
+
-- to_json, timestamps
select to_json(timestamp '2014-05-28 12:22:35.614298');
to_json
diff --git a/src/test/regress/sql/json.sql b/src/test/regress/sql/json.sql
index bc8bb62..b687ec5 100644
--- a/src/test/regress/sql/json.sql
+++ b/src/test/regress/sql/json.sql
@@ -100,6 +100,16 @@ FROM rows q;
SELECT row_to_json(row((select array_agg(x) as d from generate_series(5,10) x)),false);
+WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
+ (10,NULL, NULL),
+ (NULL, NULL, NULL)) g(a,b,c))
+ SELECT row_to_json(x, false, false) FROM x;
+
+WITH x AS (SELECT a,b,c FROM (VALUES(10,20,30),
+ (10,NULL, NULL),
+ (NULL, NULL, NULL)) g(a,b,c))
+ SELECT row_to_json(x, false, true) FROM x;
+
-- to_json, timestamps
select to_json(timestamp '2014-05-28 12:22:35.614298');
--
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