How to create and store array of objects in postgresql - postgresql

Question

In postgresql allowed array types or integer and text.But i need to create array of objects.how can i do that.
myarray text[]; //for text ['a','b','c']
myarray integer[]; //for integer[1,2,3]
I need to create the array like below
[{'dsad':1},{'sdsad':34.6},{'sdsad':23}]
I dont want to use JSON type.Using array type i need to store the array of objects.

Answer 1

If you're running Postgres 9.2+, you can use the JSON type.
For example, we could do
create table jsontest (id serial primary key, data json);
insert into jsontest (data) values ('[{"dsad":1},{"sdsad":34.6},{"sdsad":23}]');
And query the data with
select data->1 from jsontest;
{"sdsad":34.6}

Answer 2

You say:
I dont want to use JSON type
but you cannot use an ordinary array, as PostgreSQL arrays must be of homogenous types. You can't have a 2-dimensional array of text and integer.
What you could do if you don't want to use json is to create a composite type:
CREATE TYPE my_pair AS (blah text, blah2 integer);
SELECT ARRAY[ ROW('dasd',2), ROW('sdsad', 34.6), ROW('sdsad', 23) ]::my_pair[]
which will emit:
array
----------------------------------------
{"(dasd,2)","(sdsad,35)","(sdsad,23)"}
(1 row)
If you don't want that, then json is probably your best bet. Or hstore:
SELECT hstore(ARRAY['a','b','c'], ARRAY[1,2,3]::text[])
hstore
------------------------------
"a"=>"1", "b"=>"2", "c"=>"3"
(1 row)

Answer 3

JSON is your preferred answer, but more info as to why.
You can do something like:
SELECT array_agg(v)
FROM mytable v;
However you get something that looks like this:
{"(dsad,1)","(sdsad,34.6)","(""sdsad,var"",23)"}
It is then up to you to know how to decode this (i.e. column order). This is possible to do programmatically but is much easier with JSON.

Answer 4

It's hacky, but what about using an array for each property in the object (and its corresponding scalar type). If you have a data model layer in your get/read you could put the arrays "back together" into an array of objects and in your save method you would break you objects apart into synchronized arrays. This might be complicated by your example of each object not having the same properties; IDK how you'd store undefined for a property unless you're willing for null to be the same semantically.

Answer 5

It's not entirely clear if you mean json:
# select '[{"dsad":1},{"sdsad":34.6},{"sdsad":23}]'::json;
json
------------------------------------------
[{"dsad":1},{"sdsad":34.6},{"sdsad":23}]
(1 row)
Or an array of json:
# select array['{"dsad":1}', '{"sdsad":34.6}', '{"sdsad":23}']::json[];
array
------------------------------------------------------
{"{\"dsad\":1}","{\"sdsad\":34.6}","{\"sdsad\":23}"}
(1 row)
Or perhaps hstore? If the latter, it's only for key-values pairs, but you can likewise use an array of hstore values.

Answer 6

You can do something like:
SELECT JSON_AGG(v) FROM mytable v;
However you get something that looks like this:
["00000000-0000-0000-0000-000000000001","00000000-0000-0000-0000-000000000002", "00000000-0000-0000-0000-000000000003"]
exemple :
SELECT title, (select JSON_AGG(v.video_id) FROM videos v WHERE v.channel_id = c.channel_id) AS videos FROM channel AS c

Answer 7

Use text[] myarray insted of myarray text[].