On 8/18/2004 12:46 PM, Tom Lane wrote:
Jan Wieck <[EMAIL PROTECTED]> writes:If we allow for a unique index, that
* it is NOT maintained (no index tuples in there)
* depends on another index that has a subset of columns
* if that subset-index is dropped, the index becomes maintained
then the uncertainty is gone. At the time someone drops the other constraint or unique index, the data is unique with respect to the superset of columns. So building the unique index data at that time will succeed.
My goodness this is getting ugly. The notion of having to invoke an index build as a side-effect of a DROP sounds like a recipe for trouble.
The idea sure needs some refinement :-)
I'd like to see more than one person needing it, before we go to that kind of trouble to do something that's not in the spec.
Actually, the whole thing strikes me more as a sign for a denormalized database schema.
If a.x is unique, then (b.x, b.y) references (a.x, a.y) is only ensuring that the redundant copy of y in b.y stays in sync with a.y.
Jan
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