[eclipselink-users] @TableGenerator interaction with out-of-band apps

[Laird Nelson <ljnelson@xxxxxxxxx>]

Hello; quick question about the implications of a third-party application doing direct database writes while a @TableGenerator is in effect.

We have a script that does some data conversion.  It is (I think) as good a citizen as it can be--it reads the sequence table that we've constructed and referred to elsewhere in our application with the @TableGenerator annotation, and takes great care to not reuse identifiers that have already been "claimed" by the JPA id generation process.

But obviously it doesn't know what conceptual "block" of identifiers the JPA provider has already reserved.  What I mean is, suppose the JPA provider reads the sequence table in conceptual blocks of 50.  If this script comes along and inserts a row in a table somewhere then even if it reads the same sequence table and interprets it properly, there's still the possibility it's going to overlap its identity assignments with those dished out by the JPA provider.

Are there any recommendations here?

What occurred to me was to make sure that the script is at least:

1. reading the high water mark
2. reading the block size
3. pessimistically locking the high water mark column then updating it with the new value

Am I missing anything?  Are there additional concerns I haven't thought of?

Best,

Laird

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