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

>>>>>>
>>>>>> +1. If we consider some more names for that column then probably one
>>>>>> alternative could be "empty pages".
>>>>>
>>>>> Yeah, but I think "unused" might be better. Because a page could be
>>>>> in use (as an overflow page or primary bucket page) and still be
>>>>> empty.
>>>>>
>>>>
>>>> Based on the earlier discussions, I have prepared a patch that would
>>>> allow pgstathashindex() to show the number of unused pages in hash
>>>> index. Please find the attached patch for the same. Thanks.
>>>>
>>>
>>> else if (opaque->hasho_flag & LH_BITMAP_PAGE)
>>> stats.bitmap_pages++;
>>> + else if (PageIsEmpty(page))
>>> + stats.unused_pages++;
>>>
>>> I think having this check after PageIsNew() makes more sense then
>>> having at the place where you currently have,
>>
>> I don't think having it just below PageIsNew() check would be good.
>> The reason being, there can be a bucket page which is in use but still
>> be empty. So, if we add a check just below PageIsNew check then even
>> though a page is marked as bucket page and is empty it will be shown
>> as unused page which i feel is not correct. Here is one simple example
>> that illustrates this point,
>>
>
> oh, is it a page where all the items have been deleted and no new
> items have been inserted?

Yes, it is a page from where items have been removed and no new
insertion has happened.

The reason why I have told that place is
> not appropriate is because all the other checks in near by code are on
> the page type and this check looks odd at that place, but we might
> need to do this way if there is no other clean solution.

I got your point but then i think that is the only one solution we
have as of now.

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com