Re: Question regarding the database page layout. - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Question regarding the database page layout.
Date
Msg-id 14022.1220368072@sss.pgh.pa.us
Whole thread Raw
In response to Re: Question regarding the database page layout.  ("Ryan Bradetich" <rbradetich@gmail.com>)
Responses Re: Question regarding the database page layout.  (Gregory Stark <stark@enterprisedb.com>)
Re: Question regarding the database page layout.  ("Ryan Bradetich" <rbradetich@gmail.com>)
List pgsql-hackers
"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


pgsql-hackers by date:

Previous
From: "Pavel Stehule"
Date:
Subject: Re: Is this really really as designed or defined in some standard
Next
From: Gregory Stark
Date:
Subject: Re: [PATCH] Cleanup of GUC units code