Searching jsonb array in PostgreSQL - regex

Question

I'm trying to search a JSONB object in PostgreSQL 9.4. My question is similar to this thread.
However my data structure is slightly different which is causing me problems. My data structure is like:
[
{"id":1, "msg":"testing"}
{"id":2, "msg":"tested"}
{"id":3, "msg":"nothing"}
]
and I want to search for matching objects in that array by msg (RegEx, LIKE, =, etc). To be more specific, I want all rows in the table where the JSONB field has an object with a "msg" that matches my request.
The following shows a structure similar to what I have:
SELECT * FROM
(SELECT
'[{"id":1,"msg":"testing"},{"id":2,"msg":"tested"},{"id":3,"msg":"nothing"}]'::jsonb as data)
as jsonbexample;
This shows an attempt to implement the answer to the above link, but does not work (returns 0 rows):
SELECT * FROM
(SELECT
'[{"id":1,"msg":"testing"},{"id":2,"msg":"tested"},{"id":3,"msg":"nothing"}]'::jsonb as data)
as jsonbexample
WHERE
(data #>> '{msg}') LIKE '%est%';
Can anyone explain how to search through a JSONB array? In the above example I would like to find any row in the table whose "data" JSONB field contains an object where "msg" matches something (for example, LIKE '%est%').
Update
This code creates a new type (needed for later):
CREATE TYPE AlertLine AS (id INTEGER, msg TEXT);
Then you can use this to rip apart the column with JSONB_POPULATE_RECORDSET:
SELECT * FROM
JSONB_POPULATE_RECORDSET(
null::AlertLine,
(SELECT '[{"id":1,"msg":"testing"},
{"id":2,"msg":"tested"},
{"id":3,"msg":"nothing"}]'::jsonb
as data
)
) as jsonbex;
Outputs:
id | msg
----+---------
1 | testing
2 | tested
3 | nothing
And putting in the constraints:
SELECT * FROM
JSONB_POPULATE_RECORDSET(
null::AlertLine,
(SELECT '[{"id":1,"msg":"testing"},
{"id":2,"msg":"tested"},
{"id":3,"msg":"nothing"}]'::jsonb
as data)
) as jsonbex
WHERE
msg LIKE '%est%';
Outputs:
id | msg
---+---------
1 | testing
2 | tested
So the part of the question still remaining is how to put this as a clause in another query.
So, if the output of the above code = x, how would I ask:
SELECT * FROM mytable WHERE x > (0 rows);

Answer 1

You can use exists:
SELECT * FROM
(SELECT
'[{"id":1,"msg":"testing"},{"id":2,"msg":"tested"},{"id":3,"msg":"nothing"}]'::jsonb as data)
as jsonbexample
WHERE
EXISTS (SELECT 1 FROM jsonb_array_elements(data) as j(data) WHERE (data#>> '{msg}') LIKE '%est%');
To query table as mentioned in comment below:
SELECT * FROM atable
WHERE EXISTS (SELECT 1 FROM jsonb_array_elements(columnx) as j(data) WHERE (data#>> '{msg}') LIKE '%est%');