Markus Schiltknecht wrote:
Andrew Dunstan wrote:
David Fetter wrote:
That would be where the provably-distinct part comes in, so yes.

That assumes you can provide some provably distinct test. In the general case I have in mind that isn't so.

Could you please give a somewhat more concrete example, I'm not following here.

What I'm asking about has nothing much to do with partitioning.

Say I have two tables, each with a field FKed to a field in a third table. I'd like to create the values to be unique across the referring tables. Now, there are various tricks that can be played either with custom triggers or redundant data to do this, but there's no easy way. However, a multi-table unique index would do it for me quite nicely, if we could create such a thing.

However, I don't know how to set up a test for provable distinctness in this general case.

I guess my point was really that multi-table indexes might have uses beyond partitioning.



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