CiviCRM Community Forums (archive)

Great to see the start of a logging feature. I can definitely see where that will build CiviCRM's stature in many use cases. But anyway: a quick question about how you intend the logging data to be used. I observe that each logging table appears to receive two new rows/entries each time a contact is changed. One row contains the old contact data values and one contains the new ones. But how is program code supposed to differentiate between those two rows, aside from the implicit sequence in which they appear in the MySQL table (when no ORDER clause is present)? The rows show identical log_date and log_action data.

As an example: the following sequential rows (omitting some columns) in log_civicrm_email:

| id | contact_id | email                                    | is_primary | log_date            | log_conn_id | log_user_id | log_action     |
|  3 |          2 | jblade3@test0509028.com                  |          0 | 2010-11-10 01:49:32 |         367 |           1 | Update         |
|  3 |          2 | jblade4@test0509028.com                  |          1 | 2010-11-10 01:49:32 |         367 |           1 | Update         |
|  3 |          2 | jblade4@test0509028.com                  |          0 | 2010-11-10 02:02:33 |         381 |           1 | Update         |
|  3 |          2 | jblade5@test0509028.com                  |          1 | 2010-11-10 02:02:33 |         381 |           1 | Update         |

Those four rows were created when I changed the contact's email to jblade4 in one update action, then changed it again to jblade5 in another update action.  I'm guessing there are two rows per update action so that I can grab any rows for a particular timestamp and compare the two for differences easily, but how is my program code going to know which of the two is the "new" value and which is the "old" value?


Another way, perhaps, to put this is: do you already have a function somewhere that can construct a  "version" of a contact from the log_civicrm_ tables (based presumably on a timestamp), and/or to diff between versions?