Re: pageinspect: Hash index support

On Tue, Jan 24, 2017 at 11:41 AM, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
>>> Secondly, we will have to input overflow block number as an input to
>>> this function so as to determine the overflow bit number which can be
>>> used further to identify the bitmap page.
>>>
>>
>> I think you can get that from bucket number by using BUCKET_TO_BLKNO.
>> You can get bucket number from page's opaque data. So, if we follow
>> that then you can have a prototype of a function as
>> hash_bitmap_info(index_oid, page bytea) which will be quite similar to
>> other API's exposed by this module.
>>
>
> AFAIU, BUCKET_TO_BLKNO will give us the block number of a primary
> bucket page rather than overflow page and what we want is an overflow
> block number so as to determine the overflow bit number which can be
> used further to identify the bitmap page.
>

Right.

> If we pass overflow page as
> an input to hash_bitmap_info() we won't be able to get it's block
> number.
>

I think we can get it by using its prev block number, but not sure if
it is worth the complexity, so let's keep the interface as proposed by
you. TBH, I am not sure how important is to expose this
(hash_bitmap_info()) function, but let's keep it and see if committer
has any opinion on this API.

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