* Gnanakumar:
>> Just create a unique index on EMAIL column and handle error if it comes
>
> Thanks for your suggestion. Of course, I do understand that this could be
> enforced/imposed at the database-level at any time. But I'm trying to find
> out whether this could be solved at the application layer itself. Any
> thoughts/ideas?
If you use serializable transactions in PostgreSQL 9.1, you can
implement such constraints in the application without additional
locking. However, with concurrent writes and without an index, the rate
of detected serialization violations and resulting transactions aborts
will be high.
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