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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Jesper Pedersen <jesper.pedersen@redhat.com>
Cc: Michael Paquier <michael.paquier@gmail.com>
Cc: Ashutosh Sharma <ashu.coek88@gmail.com>
Cc: Jeff Janes <jeff.janes@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: pageinspect: Hash index support
Date: Fri, 23 Sep 2016 08:41:38 -0400
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On 9/23/16 1:56 AM, Amit Kapila wrote:
> On Fri, Sep 23, 2016 at 9:40 AM, Peter Eisentraut
>> - hash_metap result fields spares and mapp should be arrays of integer.
>>
> 
> how would you like to see both those arrays in tuple, right now, I
> think Jesper's code is showing it as string.

I'm not sure what you are asking here.

>> (Incidentally, the comment in hash.h talks about bitmaps[] but I think
>> it means hashm_mapp[].)
>>
> 
> which comment are you referring here?  hashm_mapp contains block
> numbers of bitmap pages.

The comment I'm referring to says

    The blknos of these bitmap pages are kept in bitmaps[]; nmaps is the
    number of currently existing bitmaps.

But there is no "bitmaps" field anywhere.

> In the above code, it appears that you are trying to calculate
> max_avail space for all pages in same way.  Don't you need to
> calculate it differently for bitmap page or meta page as they don't
> share the same format as other type of pages?

Is this even useful for hash indexes?  This idea came from btrees.
Neither the gin nor the brin code have this.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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