Re: Add pgstathashindex() to get hash index table statistics.

On Tue, Feb 7, 2017 at 2:04 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Sun, Feb 5, 2017 at 11:36 PM, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
>>> Committed with those changes.
>>
>> Thanks for above corrections and commit. But, There are couple of
>> things that we might have to change once the patch for 'WAL in Hash
>> Indexes' gets checked-in.
>>
>> 1) The test-case result needs to be changed because there won't be any
>> WARNING message : "WARNING: hash indexes are not WAL-logged and their
>> use is discouraged".
>>
>> 2) From WAL patch for Hash Indexes onwards, we won't have any zero
>> pages in Hash Indexes so I don't think we need to have column showing
>> zero pages (zero_pages). When working on WAL in hash indexes, we found
>> that WAL routine 'XLogReadBufferExtended' does not expect a page to be
>> completely zero page else it returns Invalid Buffer. To fix this, we
>> started initializing freed overflow page and newly allocated bucket
>> pages using _hash_pageinit() hence I don't think there will be any
>> zero pages from here onwards.
>
> Maybe we should call them "unused pages".
>

+1. If we consider some more names for that column then probably one
alternative could be "empty pages".

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com