[PATCH] hstore_to_json: empty hstores must return empty json objects - Mailing list pgsql-hackers

hstore_to_json used to return an empty string for empty hstores, but
that is not correct as an empty string is not valid json and calling
row_to_json() on rows which have empty hstores will generate invalid
json for the entire row.  The right thing to do is to return an empty
json object.

Signed-off-by: Oskari Saarenmaa <os@ohmu.fi>
---
This should probably be applied to 9.3 tree as well as master.

# select row_to_json(r.*) from (select ''::hstore as d) r;{"d":}

# select hstore_to_json('')::text::json;
ERROR:  invalid input syntax for type json
contrib/hstore/expected/hstore.out | 12 ++++++++++++contrib/hstore/hstore_io.c         |  8
++++----contrib/hstore/sql/hstore.sql     |  2 ++3 files changed, 18 insertions(+), 4 deletions(-)
 

diff --git a/contrib/hstore/expected/hstore.out b/contrib/hstore/expected/hstore.out
index 2114143..3280b5e 100644
--- a/contrib/hstore/expected/hstore.out
+++ b/contrib/hstore/expected/hstore.out
@@ -1472,6 +1472,18 @@ select hstore_to_json_loose('"a key" =>1, b => t, c => null, d=> 12345, e => 012 {"b": true,
"c":null, "d": 12345, "e": "012345", "f": 1.234, "g": 2.345e+4, "a key": 1}(1 row)
 
+select hstore_to_json('');
+ hstore_to_json 
+----------------
+ {}
+(1 row)
+
+select hstore_to_json_loose('');
+ hstore_to_json_loose 
+----------------------
+ {}
+(1 row)
+create table test_json_agg (f1 text, f2 hstore);insert into test_json_agg values ('rec1','"a key" =>1, b => t, c =>
null,d=> 12345, e => 012345, f=> 1.234, g=> 2.345e+4'),       ('rec2','"a key" =>2, b => f, c => "null", d=> -12345, e
=>012345.6, f=> -1.234, g=> 0.345e-4');
 
diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index d3e67dd..3781a71 100644
--- a/contrib/hstore/hstore_io.c
+++ b/contrib/hstore/hstore_io.c
@@ -1241,8 +1241,8 @@ hstore_to_json_loose(PG_FUNCTION_ARGS)    if (count == 0)    {
-        out = palloc(1);
-        *out = '\0';
+        out = palloc(3);
+        memcpy(out, "{}", 3);        PG_RETURN_TEXT_P(cstring_to_text(out));    }
@@ -1370,8 +1370,8 @@ hstore_to_json(PG_FUNCTION_ARGS)    if (count == 0)    {
-        out = palloc(1);
-        *out = '\0';
+        out = palloc(3);
+        memcpy(out, "{}", 3);        PG_RETURN_TEXT_P(cstring_to_text(out));    }
diff --git a/contrib/hstore/sql/hstore.sql b/contrib/hstore/sql/hstore.sql
index 68b74bf..47cbfad 100644
--- a/contrib/hstore/sql/hstore.sql
+++ b/contrib/hstore/sql/hstore.sql
@@ -335,6 +335,8 @@ select count(*) from testhstore where h = 'pos=>98, line=>371, node=>CBA, indexeselect
hstore_to_json('"akey" =>1, b => t, c => null, d=> 12345, e => 012345, f=> 1.234, g=> 2.345e+4');select cast( hstore
'"akey" =>1, b => t, c => null, d=> 12345, e => 012345, f=> 1.234, g=> 2.345e+4' as json);select
hstore_to_json_loose('"akey" =>1, b => t, c => null, d=> 12345, e => 012345, f=> 1.234, g=> 2.345e+4');
 
+select hstore_to_json('');
+select hstore_to_json_loose('');create table test_json_agg (f1 text, f2 hstore);insert into test_json_agg values
('rec1','"akey" =>1, b => t, c => null, d=> 12345, e => 012345, f=> 1.234, g=> 2.345e+4'),
 
-- 
1.8.3.1