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Let’s imagine I have two processes A and B performing transactions on a H2 database table T.
Process A performs CRUD (Create, Read, Update, Delete) on T.
Process B wants to know when line L in T has been last modified (i.e., B provides a System.currentTimeMillis() value for example).
One could create a column in T registering the last modification moment for each line, but I was wondering whether H2 was already holding this information somewhere and whether it can be accessed.
For my knowledge there is no such feature in H2 (and probably not in any RDBMS). The reason is simple – extra 4 or 8 bytes per each record might have a huge impact on overall database size, especially with small records. Also there will be a slight performance impact.
But it is relatively simple to implement this feature by using extra column and on update trigger. Also some databases might simplify it even further, like MySQL:
Also please distinguish between database server clock, process A clock and process B clock. In real world they most likely won’t be the same.