Обсуждение: replacing jsonb field value

using 9.4.2

suppose we have
create table test (id serial primary key, data jsonb);
insert into test (data) values ({"a":1, "b":2})

want to replace "b" with 3

okay, we are retrieving entire record
res = select * from test where data ->> b = 2

newrec = res
newrec["b" = 3

delete from test where data ->> b= 2
insert into test (data) values (newrec)

is this the best way until upsert arrives ?

On Sat, May 30, 2015 at 11:52 AM, john.tiger <john.tigernassau@gmail.com> wrote:
> using 9.4.2
>
> suppose we have
> create table test (id serial primary key, data jsonb);
> insert into test (data) values ({"a":1, "b":2})
>
> want to replace "b" with 3
>
> okay, we are retrieving entire record
> res = select * from test where data ->> b = 2
>
> newrec = res
> newrec["b" = 3
>
> delete from test where data ->> b= 2
> insert into test (data) values (newrec)
>
> is this the best way until upsert arrives ?

Append the new value to it the existing field, jsonb has as property
to enforce key uniqueness, and uses the last value scanned for a given
key.
--
Michael

Michael Paquier <michael.paquier@gmail.com> wrote:

>
> Append the new value to it the existing field, jsonb has as property
> to enforce key uniqueness, and uses the last value scanned for a given
> key.

can you show a simple example, how to append a jsonb to an jsonb-field?
Maybe i'm blind, but i can't find how it works.

Thx.


Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

----- Original Message -----
> From: Andreas Kretschmer <akretschmer@spamfence.net>
> To: pgsql-general@postgresql.org
> Cc:
> Sent: Saturday, 30 May 2015, 13:10
> Subject: Re: [GENERAL] replacing jsonb field value
>
> Michael Paquier <michael.paquier@gmail.com> wrote:
>
>>
>>  Append the new value to it the existing field, jsonb has as property
>>  to enforce key uniqueness, and uses the last value scanned for a given
>>  key.
>
> can you show a simple example, how to append a jsonb to an jsonb-field?
> Maybe i'm blind, but i can't find how it works.
>
> Thx.
>

>
> Andreas

Prior to 9.5 you can't, I think you have to use something like jsonb_each to unwrap it then wrap it back up again.

The jsonbx extension, which I believe is what ended up in 9.5 has a simple concatenate function (here:
https://github.com/erthalion/jsonbx),I also had a go (here: https://github.com/glynastill/pg_jsonb_opx). 

Glyn Astill <glynastill@yahoo.co.uk> wrote:

> Prior to 9.5 you can't, I think you have to use something like jsonb_each to unwrap it then wrap it back up again.
>
> The jsonbx extension, which I believe is what ended up in 9.5 has a simple concatenate function (here:
https://github.com/erthalion/jsonbx),I also had a go (here: https://github.com/glynastill/pg_jsonb_opx). 

Thanks.


Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

On Sat, May 30, 2015 at 9:10 PM, Andreas Kretschmer
<akretschmer@spamfence.net> wrote:
> Michael Paquier <michael.paquier@gmail.com> wrote:
>
>>
>> Append the new value to it the existing field, jsonb has as property
>> to enforce key uniqueness, and uses the last value scanned for a given
>> key.
>
> can you show a simple example, how to append a jsonb to an jsonb-field?
> Maybe i'm blind, but i can't find how it works.

You need some extra magic to do it in 9.4, for example that (not the
best performer by far that's simple enough):
=# CREATE FUNCTION jsonb_append(jsonb, jsonb)
   RETURNS jsonb AS $$
     WITH json_union AS
       (SELECT * FROM jsonb_each_text($1)
          UNION ALL
        SELECT * FROM jsonb_each_text($2))
     SELECT json_object_agg(key, value)::jsonb FROM json_union;
   $$ LANGUAGE SQL;
CREATE FUNCTION
=# SELECT jsonb_append('{"a1":"v1", "a2":"v2"}', '{"a1":"b1"}');
       jsonb_append
--------------------------
 {"a1": "b1", "a2": "v2"}
(1 row)
Googling would show up more performant functions for sure, usable with
9.4, and there is even jsonbx.
--
Michael