Re: Hard problem with concurrency

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Solution one: use sequences for the unique value.

Solution two: use another table to effect the exclusive locking
and use it to store the "unique" values:

begin;
update row;
if (no rows affected) {
lock table foo in exclusive mode;
find a unique value that is not already in foo
store this value inside of foo
insert row;
}
commit;

Solution three: use your strategy two, but throw a loop around it and have
it try again (with a new value) if it gets a unique violation.

- --
Greg Sabino Mullane greg(at)turnstep(dot)com
PGP Key: 0x14964AC8 200302162143

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