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 rows in 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 built on 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 a function 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 either type, 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
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