From: Zdenek Kotala <Zdenek.Kotala@Sun.COM>
To: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: PostgreSQL-patches <pgsql-patches@postgresql.org>
Subject: Re: page macros cleanup
Date: Fri, 04 Jul 2008 12:50:55 +0200
Message-ID: <486E008F.3080304@sun.com> (raw)
In-Reply-To: <486DF644.4070604@enterprisedb.com>
References: <48529B83.9010907@sun.com>
<2e78013d0807030450m4cab60d0jd99d1acce59fae56@mail.gmail.com>
<486DD1D1.50604@sun.com>
<2e78013d0807040150w393ad72codaf06a6ac12a83ce@mail.gmail.com>
<486DF644.4070604@enterprisedb.com>
Heikki Linnakangas napsal(a):
> Pavan Deolasee wrote:
>> On Fri, Jul 4, 2008 at 1:01 PM, Zdenek Kotala <Zdenek.Kotala@sun.com>
>> wrote:
>>>
>>> Good catch. I lost in basic arithmetic. What I see now that original
>>> definition count sizeof(ItemIdData) twice and on other side it does
>>> not take
>>> care about MAXALING correctly. I think correct formula is:
>>>
>>> #define HashMaxItemSize(page) \
>>> (PageGetPageSize(page) - \
>>> ( MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData))+ \
>>> MAXALIGN(sizeof(HashPageOpaqueData)) \
>>> )\
>>> )
>>>
>>> What do you think?
>>
>> Yes. I think that's the correct way.
>
> Doesn't look right to me. There's no padding after the first line
> pointer, hence the first MAXALIGN shouldn't be there.
Are you sure? I expecting that tupleheader must be aligned to MAXALIGN. If it is
not required than you are right.
Look on PageAddItem:
00226 alignedSize = MAXALIGN(size);
00227
00228 upper = (int) phdr->pd_upper - (int) alignedSize;
By my opinion first place where tuple should be placed is:
MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData))
> BTW, looking at hashinsert.c where it's used, we're actually passing a
> pointer to the meta page to HashMaxItemSize(). So the PageGetPageSize()
> call on that is quite bogus, since it's not the meta page that the tuple
> is going to be inserted to. It's academical, because all pages are the
> same size anyway, but doesn't look right. I think I'd go with BLKCSZ
> instead.
>
Yeah, BLKCSZ looks good. Anyway, I plan to reorganize all *MaxItemSize staff to
be compatible with in-place upgrade.
thanks Zdenek
--
Zdenek Kotala Sun Microsystems
Prague, Czech Republic http://sun.com/postgresql
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Cc: Zdenek.Kotala@Sun.COM, heikki@enterprisedb.com, pavan.deolasee@gmail.com
Subject: Re: page macros cleanup
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