text: CREATE TABLE logs (
    record jsonb,
    group_id int
  );
  
  CREATE INDEX pgroonga_index ON logs
    USING pgroonga ((record->'host'))
    WHERE group_id = 1;
  
  INSERT INTO logs VALUES ('{"host": "www"}',      1);
  INSERT INTO logs VALUES ('{"message": "error"}', 1);
  INSERT INTO logs VALUES ('{"host": "www"}',      2);
  
  SET enable_seqscan = off;
  SET enable_indexscan = off;
  SET enable_bitmapscan = on;
  
  EXPLAIN (COSTS OFF)
  SELECT * FROM logs WHERE group_id = 1;
  
  SELECT * FROM logs WHERE group_id = 1;
  
  DROP TABLE logs;
  