On 10/26/2014 04:22 PM, Pavel Stehule wrote:
2014-10-26 21:18 GMT+01:00 Andrew Dunstan <and...@dunslane.net
<mailto:and...@dunslane.net>>:
On 10/26/2014 04:14 PM, Thom Brown wrote:
On 26 October 2014 20:07, Andrew Dunstan <and...@dunslane.net
<mailto:and...@dunslane.net> <mailto:and...@dunslane.net
<mailto:and...@dunslane.net>>> wrote:
On 10/26/2014 03:50 PM, Pavel Stehule wrote:
Hi
I have a question,
what is expected result of null strip of
{"a": {"b": null, "c", null"} }
?
Please remember not to top-post.
The above is not legal json, so the answer would be an error.
I believe Pavel means:
{"a": {"b": null, "c": null} }
This is the expected result:
andrew=# select json_strip_nulls('{"a": {"b": null, "c": null} }');
json_strip_nulls
------------------
{"a":{}}
(1 row)
It is NOT expected that we replace an empty object with NULL (and
then strip it if it's a field value of an outer level object).
ok,
This case should be in regress test probably
Patch attached.
cheers
andrew
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7e5bcd9..352b408 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -10716,6 +10716,19 @@ table2-mapping
</programlisting>
</entry>
</row>
+ <row>
+ <entry><para><literal>json_strip_nulls(from_json json)</literal>
+ </para><para><literal>jsonb_strip_nulls(from_json jsonb)</literal>
+ </para></entry>
+ <entry><para><type>json</type></para><para><type>jsonb</type></para></entry>
+ <entry>
+ Returns <replaceable>from_json</replaceable>
+ with all object fields that have null values omitted. Other null values
+ are untouched.
+ </entry>
+ <entry><literal>json_strip_nulls('[{"f1":1,"f2":null},2,null,3]')</literal></entry>
+ <entry><literal>[{"f1":1},2,null,3]</literal></entry>
+ </row>
</tbody>
</tgroup>
</table>
@@ -10752,6 +10765,16 @@ table2-mapping
</para>
</note>
+ <note>
+ <para>
+ If the argument to <literal>json_strip_nulls</> contains duplicate
+ field names in any object, the result could be semantically somewhat
+ different, depending on the order in which they occur. This is not an
+ issue for <literal>jsonb_strip_nulls</> since jsonb values never have
+ duplicate object field names.
+ </para>
+ </note>
+
<para>
See also <xref linkend="functions-aggregate"> for the aggregate
function <function>json_agg</function> which aggregates record
diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 2d00dbe..06db3e4 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -105,6 +105,15 @@ static void populate_recordset_object_end(void *state);
static void populate_recordset_array_start(void *state);
static void populate_recordset_array_element_start(void *state, bool isnull);
+/* semantic action functions for json_strip_nulls */
+static void sn_object_start(void *state);
+static void sn_object_end(void *state);
+static void sn_array_start(void *state);
+static void sn_array_end(void *state);
+static void sn_object_field_start (void *state, char *fname, bool isnull);
+static void sn_array_element_start (void *state, bool isnull);
+static void sn_scalar(void *state, char *token, JsonTokenType tokentype);
+
/* worker function for populate_recordset and to_recordset */
static Datum populate_recordset_worker(FunctionCallInfo fcinfo, const char *funcname,
bool have_record_arg);
@@ -225,6 +234,13 @@ typedef struct PopulateRecordsetState
MemoryContext fn_mcxt; /* used to stash IO funcs */
} PopulateRecordsetState;
+/* state for json_strip_nulls */
+typedef struct StripnullState{
+ JsonLexContext *lex;
+ StringInfo strval;
+ bool skip_next_null;
+} StripnullState;
+
/* Turn a jsonb object into a record */
static void make_row_from_rec_and_jsonb(Jsonb *element,
PopulateRecordsetState *state);
@@ -2996,3 +3012,184 @@ findJsonbValueFromContainerLen(JsonbContainer *container, uint32 flags,
return findJsonbValueFromContainer(container, flags, &k);
}
+
+/*
+ * Semantic actions for json_strip_nulls.
+ *
+ * Simply repeat the input on the output unless we encounter
+ * a null object field. State for this is set when the field
+ * is started and reset when the scalar action (which must be next)
+ * is called.
+ */
+
+static void
+sn_object_start(void *state)
+{
+ StripnullState *_state = (StripnullState *) state;
+ appendStringInfoCharMacro(_state->strval, '{');
+}
+
+static void
+sn_object_end(void *state)
+{
+ StripnullState *_state = (StripnullState *) state;
+ appendStringInfoCharMacro(_state->strval, '}');
+}
+
+static void
+sn_array_start(void *state)
+{
+ StripnullState *_state = (StripnullState *) state;
+ appendStringInfoCharMacro(_state->strval, '[');
+}
+
+static void
+sn_array_end(void *state)
+{
+ StripnullState *_state = (StripnullState *) state;
+ appendStringInfoCharMacro(_state->strval, ']');
+}
+
+static void
+sn_object_field_start (void *state, char *fname, bool isnull)
+{
+ StripnullState *_state = (StripnullState *) state;
+
+ if (isnull)
+ {
+ /*
+ * The next thing must be a scalar or isnull couldn't be true,
+ * so there is no danger of this state being carried down
+ * into a nested object or array. The flag will be reset in the
+ * scalar action.
+ */
+ _state->skip_next_null = true;
+ return;
+ }
+
+ if (_state->strval->data[_state->strval->len - 1] != '{')
+ appendStringInfoCharMacro(_state->strval, ',');
+
+ /*
+ * Unfortunately we don't have the quoted and escaped string any more,
+ * so we have to re-escape it.
+ */
+ escape_json(_state->strval,fname);
+
+ appendStringInfoCharMacro(_state->strval, ':');
+}
+
+static void
+sn_array_element_start (void *state, bool isnull)
+{
+ StripnullState *_state = (StripnullState *) state;
+
+ if (_state->strval->data[_state->strval->len - 1] != '[')
+ appendStringInfoCharMacro(_state->strval, ',');
+}
+
+static void
+sn_scalar(void *state, char *token, JsonTokenType tokentype)
+{
+ StripnullState *_state = (StripnullState *) state;
+
+ if (_state->skip_next_null)
+ {
+ Assert (tokentype == JSON_TOKEN_NULL);
+ _state->skip_next_null = false;
+ return;
+ }
+
+ if (tokentype == JSON_TOKEN_STRING)
+ escape_json(_state->strval, token);
+ else
+ appendStringInfoString(_state->strval, token);
+}
+
+/*
+ * SQL function json_strip_nulls(json) -> json
+ */
+Datum
+json_strip_nulls(PG_FUNCTION_ARGS)
+{
+ text *json = PG_GETARG_TEXT_P(0);
+ StripnullState *state;
+ JsonLexContext *lex;
+ JsonSemAction *sem;
+
+ lex = makeJsonLexContext(json, true);
+ state = palloc0(sizeof(StripnullState));
+ sem = palloc0(sizeof(JsonSemAction));
+
+ state->strval = makeStringInfo();
+ state->skip_next_null = false;
+ state->lex = lex;
+
+ sem->semstate = (void *) state;
+ sem->object_start = sn_object_start;
+ sem->object_end = sn_object_end;
+ sem->array_start = sn_array_start;
+ sem->array_end = sn_array_end;
+ sem->scalar = sn_scalar;
+ sem->array_element_start = sn_array_element_start;
+ sem->object_field_start = sn_object_field_start;
+
+ pg_parse_json(lex, sem);
+
+ PG_RETURN_TEXT_P(cstring_to_text_with_len(state->strval->data,
+ state->strval->len));
+
+}
+
+/*
+ * SQL function jsonb_strip_nulls(jsonb) -> jsonb
+ */
+Datum
+jsonb_strip_nulls(PG_FUNCTION_ARGS)
+{
+ Jsonb * jb = PG_GETARG_JSONB(0);
+ JsonbIterator *it;
+ JsonbParseState *parseState = NULL;
+ JsonbValue *res;
+ int type;
+ JsonbValue v,k;
+ bool last_was_key = false;
+
+ if (JB_ROOT_IS_SCALAR(jb))
+ PG_RETURN_POINTER(jb);
+
+ it = JsonbIteratorInit(&jb->root);
+
+ while ((type = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
+ {
+ Assert( ! (type == WJB_KEY && last_was_key));
+
+ if (type == WJB_KEY)
+ {
+ /* stash the key until we know if it has a null value */
+ k = v;
+ last_was_key = true;
+ continue;
+ }
+
+ if (last_was_key)
+ {
+ /* if the last element was a key this one can't be */
+ last_was_key = false;
+
+ /* skip this field if value is null */
+ if (type == WJB_VALUE && v.type == jbvNull)
+ continue;
+
+ /* otherwise, do a delayed push of the key */
+ res = pushJsonbValue(&parseState, WJB_KEY, &k);
+ }
+
+ if (type == WJB_VALUE || type == WJB_ELEM)
+ res = pushJsonbValue(&parseState, type, &v);
+ else
+ res = pushJsonbValue(&parseState, type, NULL);
+ }
+
+ PG_RETURN_POINTER(JsonbValueToJsonb(res));
+}
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index b6dc1b8..23f8f2f 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4237,6 +4237,8 @@ DATA(insert OID = 3203 ( json_object PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0
DESCR("map text arrays of keys and values to json object");
DATA(insert OID = 3176 ( to_json PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 114 "2283" _null_ _null_ _null_ _null_ to_json _null_ _null_ _null_ ));
DESCR("map input to json");
+DATA(insert OID = 3300 ( json_strip_nulls PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 114 "114" _null_ _null_ _null_ _null_ json_strip_nulls _null_ _null_ _null_ ));
+DESCR("remove object fields with null values from json");
DATA(insert OID = 3947 ( json_object_field PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 114 "114 25" _null_ _null_ "{from_json, field_name}" _null_ json_object_field _null_ _null_ _null_ ));
DATA(insert OID = 3948 ( json_object_field_text PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 25 "114 25" _null_ _null_ "{from_json, field_name}" _null_ json_object_field_text _null_ _null_ _null_ ));
@@ -4599,6 +4601,9 @@ DESCR("I/O");
DATA(insert OID = 3803 ( jsonb_send PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 17 "3802" _null_ _null_ _null_ _null_ jsonb_send _null_ _null_ _null_ ));
DESCR("I/O");
+DATA(insert OID = 3301 ( jsonb_strip_nulls PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 3802 "3802" _null_ _null_ _null_ _null_ jsonb_strip_nulls _null_ _null_ _null_ ));
+DESCR("remove object fields with null values from jsonb");
+
DATA(insert OID = 3478 ( jsonb_object_field PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 3802 "3802 25" _null_ _null_ "{from_json, field_name}" _null_ jsonb_object_field _null_ _null_ _null_ ));
DATA(insert OID = 3214 ( jsonb_object_field_text PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 25 "3802 25" _null_ _null_ "{from_json, field_name}" _null_ jsonb_object_field_text _null_ _null_ _null_ ));
DATA(insert OID = 3215 ( jsonb_array_element PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 3802 "3802 23" _null_ _null_ "{from_json, element_index}" _null_ jsonb_array_element _null_ _null_ _null_ ));
diff --git a/src/include/utils/json.h b/src/include/utils/json.h
index 82cc48b..cada47e 100644
--- a/src/include/utils/json.h
+++ b/src/include/utils/json.h
@@ -63,6 +63,7 @@ extern Datum json_populate_record(PG_FUNCTION_ARGS);
extern Datum json_populate_recordset(PG_FUNCTION_ARGS);
extern Datum json_to_record(PG_FUNCTION_ARGS);
extern Datum json_to_recordset(PG_FUNCTION_ARGS);
+extern Datum json_strip_nulls(PG_FUNCTION_ARGS);
extern Datum jsonb_object_field(PG_FUNCTION_ARGS);
extern Datum jsonb_object_field_text(PG_FUNCTION_ARGS);
@@ -80,5 +81,6 @@ extern Datum jsonb_populate_record(PG_FUNCTION_ARGS);
extern Datum jsonb_populate_recordset(PG_FUNCTION_ARGS);
extern Datum jsonb_to_record(PG_FUNCTION_ARGS);
extern Datum jsonb_to_recordset(PG_FUNCTION_ARGS);
+extern Datum jsonb_strip_nulls(PG_FUNCTION_ARGS);
#endif /* JSON_H */
diff --git a/src/test/regress/expected/json.out b/src/test/regress/expected/json.out
index bb4d9ed..e435d3e 100644
--- a/src/test/regress/expected/json.out
+++ b/src/test/regress/expected/json.out
@@ -1586,3 +1586,53 @@ select * from json_to_recordset('[{"a":1,"b":{"d":"foo"},"c":true},{"a":2,"c":fa
2 | {"d":"bar"} | f
(2 rows)
+-- json_strip_nulls
+select json_strip_nulls(null);
+ json_strip_nulls
+------------------
+
+(1 row)
+
+select json_strip_nulls('1');
+ json_strip_nulls
+------------------
+ 1
+(1 row)
+
+select json_strip_nulls('"a string"');
+ json_strip_nulls
+------------------
+ "a string"
+(1 row)
+
+select json_strip_nulls('null');
+ json_strip_nulls
+------------------
+ null
+(1 row)
+
+select json_strip_nulls('[1,2,null,3,4]');
+ json_strip_nulls
+------------------
+ [1,2,null,3,4]
+(1 row)
+
+select json_strip_nulls('{"a":1,"b":null,"c":[2,null,3],"d":{"e":4,"f":null}}');
+ json_strip_nulls
+------------------------------------
+ {"a":1,"c":[2,null,3],"d":{"e":4}}
+(1 row)
+
+select json_strip_nulls('[1,{"a":1,"b":null,"c":2},3]');
+ json_strip_nulls
+---------------------
+ [1,{"a":1,"c":2},3]
+(1 row)
+
+-- an empty object is not null and should not be stripped
+select json_strip_nulls('{"a": {"b": null, "c": null}, "d": {} }');
+ json_strip_nulls
+------------------
+ {"a":{},"d":{}}
+(1 row)
+
diff --git a/src/test/regress/expected/json_1.out b/src/test/regress/expected/json_1.out
index 83c1d7d..106b481 100644
--- a/src/test/regress/expected/json_1.out
+++ b/src/test/regress/expected/json_1.out
@@ -1582,3 +1582,53 @@ select * from json_to_recordset('[{"a":1,"b":{"d":"foo"},"c":true},{"a":2,"c":fa
2 | {"d":"bar"} | f
(2 rows)
+-- json_strip_nulls
+select json_strip_nulls(null);
+ json_strip_nulls
+------------------
+
+(1 row)
+
+select json_strip_nulls('1');
+ json_strip_nulls
+------------------
+ 1
+(1 row)
+
+select json_strip_nulls('"a string"');
+ json_strip_nulls
+------------------
+ "a string"
+(1 row)
+
+select json_strip_nulls('null');
+ json_strip_nulls
+------------------
+ null
+(1 row)
+
+select json_strip_nulls('[1,2,null,3,4]');
+ json_strip_nulls
+------------------
+ [1,2,null,3,4]
+(1 row)
+
+select json_strip_nulls('{"a":1,"b":null,"c":[2,null,3],"d":{"e":4,"f":null}}');
+ json_strip_nulls
+------------------------------------
+ {"a":1,"c":[2,null,3],"d":{"e":4}}
+(1 row)
+
+select json_strip_nulls('[1,{"a":1,"b":null,"c":2},3]');
+ json_strip_nulls
+---------------------
+ [1,{"a":1,"c":2},3]
+(1 row)
+
+-- an empty object is not null and should not be stripped
+select json_strip_nulls('{"a": {"b": null, "c": null}, "d": {} }');
+ json_strip_nulls
+------------------
+ {"a":{},"d":{}}
+(1 row)
+
diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index 9146f59..3e1d769 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -2472,3 +2472,53 @@ SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb ? 'e';
f
(1 row)
+-- jsonb_strip_nulls
+select jsonb_strip_nulls(null);
+ jsonb_strip_nulls
+-------------------
+
+(1 row)
+
+select jsonb_strip_nulls('1');
+ jsonb_strip_nulls
+-------------------
+ 1
+(1 row)
+
+select jsonb_strip_nulls('"a string"');
+ jsonb_strip_nulls
+-------------------
+ "a string"
+(1 row)
+
+select jsonb_strip_nulls('null');
+ jsonb_strip_nulls
+-------------------
+ null
+(1 row)
+
+select jsonb_strip_nulls('[1,2,null,3,4]');
+ jsonb_strip_nulls
+--------------------
+ [1, 2, null, 3, 4]
+(1 row)
+
+select jsonb_strip_nulls('{"a":1,"b":null,"c":[2,null,3],"d":{"e":4,"f":null}}');
+ jsonb_strip_nulls
+--------------------------------------------
+ {"a": 1, "c": [2, null, 3], "d": {"e": 4}}
+(1 row)
+
+select jsonb_strip_nulls('[1,{"a":1,"b":null,"c":2},3]');
+ jsonb_strip_nulls
+--------------------------
+ [1, {"a": 1, "c": 2}, 3]
+(1 row)
+
+-- an empty object is not null and should not be stripped
+select jsonb_strip_nulls('{"a": {"b": null, "c": null}, "d": {} }');
+ jsonb_strip_nulls
+--------------------
+ {"a": {}, "d": {}}
+(1 row)
+
diff --git a/src/test/regress/expected/jsonb_1.out b/src/test/regress/expected/jsonb_1.out
index 83d61f8..35da6f4 100644
--- a/src/test/regress/expected/jsonb_1.out
+++ b/src/test/regress/expected/jsonb_1.out
@@ -2472,3 +2472,53 @@ SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb ? 'e';
f
(1 row)
+-- jsonb_strip_nulls
+select jsonb_strip_nulls(null);
+ jsonb_strip_nulls
+-------------------
+
+(1 row)
+
+select jsonb_strip_nulls('1');
+ jsonb_strip_nulls
+-------------------
+ 1
+(1 row)
+
+select jsonb_strip_nulls('"a string"');
+ jsonb_strip_nulls
+-------------------
+ "a string"
+(1 row)
+
+select jsonb_strip_nulls('null');
+ jsonb_strip_nulls
+-------------------
+ null
+(1 row)
+
+select jsonb_strip_nulls('[1,2,null,3,4]');
+ jsonb_strip_nulls
+--------------------
+ [1, 2, null, 3, 4]
+(1 row)
+
+select jsonb_strip_nulls('{"a":1,"b":null,"c":[2,null,3],"d":{"e":4,"f":null}}');
+ jsonb_strip_nulls
+--------------------------------------------
+ {"a": 1, "c": [2, null, 3], "d": {"e": 4}}
+(1 row)
+
+select jsonb_strip_nulls('[1,{"a":1,"b":null,"c":2},3]');
+ jsonb_strip_nulls
+--------------------------
+ [1, {"a": 1, "c": 2}, 3]
+(1 row)
+
+-- an empty object is not null and should not be stripped
+select jsonb_strip_nulls('{"a": {"b": null, "c": null}, "d": {} }');
+ jsonb_strip_nulls
+--------------------
+ {"a": {}, "d": {}}
+(1 row)
+
diff --git a/src/test/regress/sql/json.sql b/src/test/regress/sql/json.sql
index c980132..36a6674 100644
--- a/src/test/regress/sql/json.sql
+++ b/src/test/regress/sql/json.sql
@@ -509,3 +509,23 @@ select * from json_to_recordset('[{"a":1,"b":"foo","d":false},{"a":2,"b":"bar","
select * from json_to_recordset('[{"a":1,"b":{"d":"foo"},"c":true},{"a":2,"c":false,"b":{"d":"bar"}}]')
as x(a int, b json, c boolean);
+
+
+-- json_strip_nulls
+
+select json_strip_nulls(null);
+
+select json_strip_nulls('1');
+
+select json_strip_nulls('"a string"');
+
+select json_strip_nulls('null');
+
+select json_strip_nulls('[1,2,null,3,4]');
+
+select json_strip_nulls('{"a":1,"b":null,"c":[2,null,3],"d":{"e":4,"f":null}}');
+
+select json_strip_nulls('[1,{"a":1,"b":null,"c":2},3]');
+
+-- an empty object is not null and should not be stripped
+select json_strip_nulls('{"a": {"b": null, "c": null}, "d": {} }');
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index f1ed021..e8e6117 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -542,3 +542,22 @@ SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb ? 'b';
SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb ? 'c';
SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb ? 'd';
SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb ? 'e';
+
+-- jsonb_strip_nulls
+
+select jsonb_strip_nulls(null);
+
+select jsonb_strip_nulls('1');
+
+select jsonb_strip_nulls('"a string"');
+
+select jsonb_strip_nulls('null');
+
+select jsonb_strip_nulls('[1,2,null,3,4]');
+
+select jsonb_strip_nulls('{"a":1,"b":null,"c":[2,null,3],"d":{"e":4,"f":null}}');
+
+select jsonb_strip_nulls('[1,{"a":1,"b":null,"c":2},3]');
+
+-- an empty object is not null and should not be stripped
+select jsonb_strip_nulls('{"a": {"b": null, "c": null}, "d": {} }');
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