{ 'order_code' => '0165-02675-4565', 'email' => 'foo@test.com', 'price' => '15', 'title' => 'Mt Thing XYZ' }; 

##</code><code>##

create index junk7_gin_idx using gin (data);

##</code><code>##

select * from junk7 where data @> '{ "email": "abcd@text.com" }';

##</code><code>##

#!/bin/sh
for power in 7;
do
  table=junk${power}
  echo "-- table $table";
  echo "drop index if exists ${table}_gin_idx" | psql -qtAX
  if [[ 1 -eq 1 ]];
  then
    time perl -E'
    sub ss{ join"",@_[ map{rand @_} 1 .. shift ] };
    say( q({{order_code, "0165-02675-4565"}, {email, ).q(").ss(4,"a".."z").q(@test.com"}, {price, "15"}, {title, "Mt Thing XYZ"}}) )
        for 1 .. 1e'"${power};" \
    | psql -aqXc "
      drop table if exists $table;
      create table $table(id serial, data jsonb, txt text);
      copy $table(txt) from stdin;
      update $table set data = cast(json_object(cast(txt as text[][])) as jsonb);
      alter table $table drop column txt;
    "
  fi
  echo "table $table limit 3"         | psql -qX # show a few rows
  echo "select count(*) from $table " | psql -qX # show rowcount
  echo "          select * from $table where data @> '{\"email\": \"abcd@test.com\"}'; -- cold cache (possibly)
                  select * from $table where data @> '{\"email\": \"abcd@test.com\"}'; -- warm cache
  explain analyze select * from $table where data @> '{\"email\": \"abcd@test.com\"}'; -- explain
  " | psql
  echo "create index ${table}_gin_idx on $table using gin (data);
        analyze $table;
  " | psql
  echo "          select * from $table where data @> '{\"email\": \"abcd@test.com\"}'; -- cold cache (possibly)
                  select * from $table where data @> '{\"email\": \"abcd@test.com\"}'; -- warm cache
  explain analyze select * from $table where data @> '{\"email\": \"abcd@test.com\"}'; -- explain
  " | psql
  echo "\dti+ ${table}*" | psql -qX
done

##</code><code>##

-- table junk7
 id |                                                data
----+-----------------------------------------------------------------------------------------------------
  1 | {"email": "syya@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
  2 | {"email": "lzda@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
  3 | {"email": "ygiu@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
(3 rows)

  count
----------
 10000000
(1 row)

   id    |                                                data
---------+-----------------------------------------------------------------------------------------------------
  408723 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
 1008165 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
[...]
 9380475 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
 9824614 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
(26 rows)

Time: 4071.469 ms
   id    |                                                data
---------+-----------------------------------------------------------------------------------------------------
  408723 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
 1008165 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
[...]
 9380475 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
 9824614 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
(26 rows)

Time: 3879.432 ms
                                                   QUERY PLAN
----------------------------------------------------------------------------------------------------------------
 Seq Scan on junk7  (cost=0.00..583103.10 rows=10004 width=108) (actual time=144.428..3894.673 rows=26 loops=1)
   Filter: (data @> '{"email": "abcd@test.com"}'::jsonb)
   Rows Removed by Filter: 9999974
 Planning time: 0.034 ms
 Execution time: 3894.709 ms
(5 rows)

CREATE INDEX
Time: 82600.671 ms

[...]

 9380475 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
 9824614 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
(26 rows)

Time: 23.768 ms
   id    |                                                data
---------+-----------------------------------------------------------------------------------------------------
  408723 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
 1008165 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
[...]
 9380475 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
 9824614 | {"email": "abcd@test.com", "price": "15", "title": "Mt Thing XYZ", "order_code": "0165-02675-4565"}
(26 rows)

Time: 4.792 ms
                                                         QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on junk7  (cost=125.49..35457.45 rows=9999 width=108) (actual time=3.412..3.490 rows=26 loops=1)
   Recheck Cond: (data @> '{"email": "abcd@test.com"}'::jsonb)
   Heap Blocks: exact=26
   ->  Bitmap Index Scan on junk7_gin_idx  (cost=0.00..122.99 rows=9999 width=0) (actual time=3.395..3.395 rows=26 loops=1)
         Index Cond: (data @> '{"email": "abcd@test.com"}'::jsonb)
 Planning time: 0.832 ms
 Execution time: 3.544 ms
(7 rows)

Time: 4.895 ms
                             List of relations
 Schema |     Name      | Type  |  Owner   | Table |  Size   | Description
--------+---------------+-------+----------+-------+---------+-------------
 public | junk7         | table | aardvark |       | 3579 MB |
 public | junk7_gin_idx | index | aardvark | junk7 | 177 MB  |
(2 rows)