It may be overkill, but you can use a database for this functionality. Both mysql and Oracle have efficient ways of loading large datasets into a pre-defined table while obeying constraints on those tables. This may not be the fastest solution, but it should ease up on the memory requirements.

MySQL LOAD DATA

Oracle SQL*Loader

In reply to Re: Strategy for randomizing large files via sysseek by RiotTown
in thread Strategy for randomizing large files via sysseek by Anonymous Monk

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