Tuesday, September 2, 2008

Re: [HACKERS] Question regarding the database page layout.

"Ryan Bradetich" <rbradetich@gmail.com> writes:
> The patch concept is fairly simple.

> 1. Add a new boolean local variable: require_max_align
> (initialized to false).

This really can't possibly work, because you'd need to propagate
knowledge of the tuple's alignment requirement all over the place.
In particular, how would code *reading* the tuple know where the
data starts? Also, I don't think you get (very much of) the actual
benefit unless the code that inserts tuples into disk pages knows
to do something different in the int-align case.

It's conceivable that we could make this work if we wanted to dedicate
an infomask bit to showing whether the tuple needs int or double
alignment. I don't really think it's worth the trouble though.

regards, tom lane

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