Question

I am working on a PHP class implementing PDO to sync a local database’s table with a remote one.

The Question

I am looking for some ideas / methods / suggestions on how to implement a ‘backup’ feature to my ‘syncing’ process. The ideas is: Before the actual insert of the data takes place, I do a full wipe of the local table’s data. Time is not a factor so I figure this is the cleanest and simplest solution and I wont have to worry about checking for differences in the data and all that jazz. The Problem is, I want to implement some kind of security measure in case there is a problem during the insert of data, like loss of internet connection or something. The only idea I have so far is: Copy said table to be synced -> wipe said table -> insert remote tables data into local table -> if successful delete backup copy.

Answer 1

Check out mk-table-sync. It compares two tables on different servers, using checksums of chunks of rows. If a given chunk is identical between the two servers, no copying is needed. If the chunk differs, it copies just the chunk it needs. You don’t have to wipe the local table.

Another alternative is to copy the remote data to a distinct table name. If it completes successfully, then DROP the old table and RENAME the new local copy to the original table’s name. If the copy fails or is interrupted, then drop the local copy with the distinct name and try again. Meanwhile, your other local table with the previous data is untouched.