Re: Null values in indexes

Tom Lane wrote:
> Hannu Krosing <hannu(at)tm(dot)ee> writes:
> > How hard would it be to _not_ include nulls in indexes
> > as they are not used anyway.
>
> Seems to me that would be a step backwards.

It would cause multi-key indexes beeing unusable for partial
key lookup. Imagine you have a key over (a, b, c) and query
with WHERE a = 1 AND b = 2. This query cannot use the index
if a NULL value in c would cause the index entry to be
suppressed.

Jan

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