Querying Postgres 9.6 JSONB array of objects

Question

I have the following table:

CREATE TABLE trip
(
    id SERIAL PRIMARY KEY ,
    gps_data_json jsonb NOT NULL
);

The JSON in gps_data_json contains an array of of trip objects with the following fields (sample data below):

• mode
• timestamp
• latitude
• longitude

I'm trying to get all rows that contain a certain "mode".

SELECT * FROM trip
where gps_data_json ->> 'mode' = 'WALK';

I pretty sure I'm using the ->> operator wrong, but I'm unsure who to tell the query that the JSONB field is an array of objects?

Sample data:

INSERT INTO trip (gps_data_json) VALUES
  ('[
      {
        "latitude": 47.063480377197266,
        "timestamp": 1503056880725,
        "mode": "TRAIN",
        "longitude": 15.450349807739258
      },
      {
        "latitude": 47.06362533569336,
        "timestamp": 1503056882725,
        "mode": "WALK",
        "longitude": 15.450264930725098
      }
    ]');

INSERT INTO trip (gps_data_json) VALUES
  ('[
      {
        "latitude": 47.063480377197266,
        "timestamp": 1503056880725,
        "mode": "BUS",
        "longitude": 15.450349807739258
      },
      {
        "latitude": 47.06362533569336,
        "timestamp": 1503056882725,
        "mode": "WALK",
        "longitude": 15.450264930725098
      }
    ]');

Answer 1

The problem arises because ->> operator cannot walk through array:

• First unnest your json array using json_array_elements function;
• Then use the operator for filtering.

Following query does the trick:

WITH 
A AS (
SELECT
    Id
   ,jsonb_array_elements(gps_data_json) AS point
FROM trip
)
SELECT *
FROM A
WHERE (point->>'mode') = 'WALK';