Feature Request: Replication capability

[deathemperor]

Copied from original request:

I really want to share our intended use case with doltgres just so you know how interested I am in this project: we do claim management and processing for insurers and data changes are part of our core data structures. At any given time we need to allow claim handlers to view those data to make decisions as well as others to view audit logs. Such use case may not be so unique, except we're using GraphQL with Hasura (been using it in our org for 3 years now) which enables instant GraphQL from postgres. With the combination of those, we'll build something like this:

create table employees (
    id int8,
    last_name text,
    first_name text,
    primary key(id));

insert into employees values 
    (0, 'Sehn', 'Tim'), 
    (1, 'Hendriks', 'Brian'), 
    (2, 'Son','Aaron'), 
    (3, 'Fitzgerald', 'Brian');

select * from employees where first_name='Brian';
+------+------------+------------+
| id   | last_name  | first_name |
+------+------------+------------+
|    1 | Hendriks   | Brian      |
|    3 | Fitzgerald | Brian      |
+------+------------+------------+

select * from dolt_diff_employees;
+--------------+---------------+-------+-----------+----------------+----------------+-----------------+---------+----------------------------------+-------------------------+-----------+
| to_last_name | to_first_name | to_id | to_commit | to_commit_date | from_last_name | from_first_name | from_id | from_commit                      | from_commit_date        | diff_type |
+--------------+---------------+-------+-----------+----------------+----------------+-----------------+---------+----------------------------------+-------------------------+-----------+
| Sehn         | Tim           |     0 | WORKING   | NULL           | NULL           | NULL            |    NULL | ne182jemgrlm8jnjmoubfqsstlfi1s98 | 2022-06-07 16:35:49.277 | added     |
+--------------+---------------+-------+-----------+----------------+----------------+-----------------+---------+----------------------------------+-------------------------+-----------+

call dolt_checkout('-b','modifications');
update employees SET first_name='Timothy' where first_name='Tim';
call dolt_commit('-am', 'Modifications on a branch');


select * from dolt_diff('main', 'modifications', 'employees');
+--------------+---------------+-------+---------------+-------------------------+----------------+-----------------+---------+-------------+-------------------------+-----------+
| to_last_name | to_first_name | to_id | to_commit     | to_commit_date          | from_last_name | from_first_name | from_id | from_commit | from_commit_date        | diff_type |
+--------------+---------------+-------+---------------+-------------------------+----------------+-----------------+---------+-------------+-------------------------+-----------+
| Sehn         | Timothy       |     0 | modifications | 2022-06-07 16:41:49.847 | Sehn           | Tim             |       0 | main        | 2022-06-07 16:39:32.066 | modified  |
| Wilkins      | Daylon        |     4 | modifications | 2022-06-07 16:41:49.847 | NULL           | NULL            |    NULL | main        | 2022-06-07 16:39:32.066 | added     |
+--------------+---------------+-------+---------------+-------------------------+----------------+-----------------+---------+-------------+-------------------------+-----------+

Graphql-join this data with the employees table, I'll get this Graph:

query test {
    employees {  // array of objects
        id
        last_name
        first_name
        dolt_diff_employees_modifications { // array of objects
            to_last_name
            to_first_name
            to_id
            to_commit
            to_commit_date
            from_last_name
            from_first_name
            from_id
            from_commit
            from_commit_date
            diff_type
        }
        dolt_diff_employees_other_modifications { // array of objects
            to_last_name
            to_first_name
            to_id
            to_commit
            to_commit_date
            from_last_name
            from_first_name
            from_id
            from_commit
            from_commit_date
            diff_type
        }
    }
}