Hi,
More generically, how do I best guarantee that any large varchar is unique
before inserting?
In my application, I need to ensure that each e-mail address and
corresponding PGP public key are both unique.
I originally implemented this by adding a uniqueness contrainst to both
columns. easy.
The problem is that some PGP keys are over 2713 bytes, and postgres (7.2)
gives the error:
ERROR: btree: index item size 4336 exceeds maximum 2713
I thought perhaps I could use a hash or rtree index, but neither of them work
for unique-ness.
I saw in another posting that it may be possible to raise this limit to 8k or
so, but I don't want to do this because 1) it requires a recompile of
postgres (and rollout to dev, stage, prod machines), and 2) a key could
theoretically be longer than 8k anyway.
I can guarantee unique-ness by removing the index and doing a select before
the insert. If there is a matching row, then I am trying to insert a dup.
bail.
My concern is that doing this without an index will be monumentally slow for
any large-ish number of keys.
Any bright ideas? All suggestions appreciated.
/andre