Re: How many fields in a table are too many

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > However, I am not sure how useful NOT NULL is in practice because there
> > are lots of columns that don't specify NOT NULL but have mostly nulls or
> > mostly non-nulls, which kills our caching --- what I was hoping to do
> > some day was to cache the null bitmask and offsets of the previous tuple
> > and use those if the new tuple has the same null bitmask as the previous
> > tuple.
>
> We already cache fairly effectively in cases where there are no nulls.
> I'm not sure it's worth trying to do something with the idea that two
> adjacent tuples might have nulls in the same places.

I was thinking of trying it and seeing how often it would be a win,
because right now, when we hit a null, our cache is dead.

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