问题
I used Oracle sequence as primary key of a table, and used int in Java application mapping this primary key, now I found my customer has reached to the maximum int in table, even the sequence can be continuous increase. but Java int has no longer able to store it, I don't want change Java code from int to long because of very big cost. then I found customer DB there have many big gaps in ID column. can any way I can reuse these missing Id number?
If can do this in DB level, something like I can re-org this sequence to add these missing number to it, so no Java code change then I can use these gaps. it should be great.
I will write a function to find the gap ranges, after having these numbers, If I can, I want assign them to pool of the sequence value, so maybe from now on, it will not use auto-incrementing, just use the number I assigned. in Java code, I can continue use findNextNumber to call the sequence. but sequence will be able to return the value I assigned to it. it seems impossible, right? any alternative?
回答1:
Do you mean, will the sequence ever return a value that is in a "gap" range? I don't think so, unless you drop/re-create it for some reason. I guess you could write a function of some sorts to find the PK gaps in your table, then save those gap ranges to another table, and "roll" your own sequence function using the gap table. Very ugly. Trying to "recover" these gaps just sounds like a desperate attempt to avoid the unavoidable - your java PK data type should have aligned with the DB data type. I had the same problem a long time ago with a VB app that had a class key defined as 16-bit integer, and the sequence exceeded 32K, had to change the variables to a Long. I say, bite the bullet, and make the conversion. A little pain now, will save you a lot of ongoing pain later. Just my opinion.
回答2:
I would definitely make the change to be able to use longer numbers, but in the meantime you might manage until you can make that change by using a sequence that generates negative numbers. There'd be a performance impact on the maintenance of the PK index, and it would grow larger disproportionately quicker, though
来源：https://stackoverflow.com/questions/15312676/how-do-i-reuse-oracle-sequence-gaps-in-primary-key-column