Re: [GENERAL] Question about jsonb and data structures

On 21/06/2017 01:01, Emilie Laffray wrote:
> Hello,
>
> I have been playing with Postgresql recently with a large table and I have started looking at reducing the number of
rowsin that table. 
> One idea to reduce the actual size, I thought I would "compress" the data structure into a JSON object (more on that
later).
> The table is pretty straightforward in itself
> other_id integer
> type_id integer
> label_id integer
> rank_id integer
> value real
>
> and the goal is to move to a data structure where we have
> other_id integer
> value jsonb
>
> There are many things in the table that is not optimal for legacy reasons and I can't just get rid of them.
>
> I looked at several json object data structure to see if I could make it work notably
> [{"type":1,"label":1,"rank":1,"value":.5},{"type":1,"label":2,"rank":1,"value":.25}]
> {"1":{"1":{"rank":1,"value":.5},"2":{"rank":1,"value":.25}}}
>
> For better or worse, the first one would be the best for me as I can do a simple query like this using the GIN index
builton top of value: 
> SELECT *
> FROM mytable
> WHERE value @> '[{"type":1,"rank":1,"label":2}]'
>
> Effectively, I would want to extract the value corresponding to my condition using simple SQL aka not having to write
afunction extracting the json. 
>
> The experiment on the second data structure shows that it is not as convenient as I may need to perform search on
eithertype, label, rank and various combinations of the fields. 
>
Maybe you could try smth like :
test=# select * from lala;
  id |    txt
----+------------
   1 | one
   2 | two
   3 | ZZZbabaZZZ
   4 | ZZZbabaZZZ
   5 | ZZZbabaZZZ
   6 | ZZZbabaZZZ
   7 | ZZZbabaZZZ
   8 | ZZZbabaZZZ
   9 | ZZZbabaZZZ
  10 | ZZZbabaZZZ
  11 | ZZZbabaZZZ
  12 | ZZZbabaZZZ
  13 | ZZZbabaZZZ
(13 rows)

select foo.* FROM (select id,to_jsonb(lala) as jzon from lala) as foo where jzon @> '{"id":5}';

> Am I missing something?
>
> Thanks in advance,
> Emilie Laffray


--
Achilleas Mantzios
IT DEV Lead
IT DEPT
Dynacom Tankers Mgmt