What's the proper index for querying structures in arrays in Postgres jsonb?

Question

I'm experimenting with keeping values like the following in a Postgres jsonb field in Postgres 9.4:

[{"event_slug":"test_1","start_time":"2014-10-08","end_time":"2014-10-12"},
 {"event_slug":"test_2","start_time":"2013-06-24","end_time":"2013-07-02"},
 {"event_slug":"test_3","start_time":"2014-03-26","end_time":"2014-03-30"}]

I'm executing queries like:

SELECT * FROM locations
WHERE EXISTS (
  SELECT 1 FROM jsonb_array_elements(events) AS e
  WHERE (
    e->>'event_slug' = 'test_1' AND
    (
      e->>'start_time' >= '2014-10-30 14:04:06 -0400' OR
      e->>'end_time' >= '2014-10-30 14:04:06 -0400'
    )
  )
)

How would I create an index on that data for queries like the above to utilize? Does this sound reasonable design for a few million rows that each contain ~10 events in that column?

Worth noting that it seems I'm still getting sequential scans with:

CREATE INDEX events_gin_idx ON some_table USING GIN (events);

which I'm guessing is because the first thing I'm doing in the query is converting data to json array elements.

Answer 1

CREATE INDEX json_array_elements_index ON
    json_array_elements ((events_arr->>'event_slug'));

Should get you started in the right direction.