Re: [HACKERS] GSoC 2017: weekly progress reports (week 4) and patchfor hash index

Thanks to everyone, pushed

Alexander Korotkov wrote:
> On Fri, Mar 2, 2018 at 6:57 AM, Thomas Munro 
> <thomas.munro@enterprisedb.com <mailto:thomas.munro@enterprisedb.com>> 
> wrote:
> 
>     My thought experiments about pseudo-pages and avoiding the split stuff
>     were not intended to get the patch kicked out.  I thought for a while
>     that hash indexes were a special case and could benefit from
>     dispensing with those trickier problems.  Upon further reflection, for
>     interesting size hash indexes pure hash value predicate tags wouldn't
>     be much better.  Furthermore, if we do decide we want to use using x %
>     max_predicate_locks_per_relation to avoid having to escalate to
>     relation predicate locks at the cost of slightly higher collision rate
>     then we should consider that for the whole system (including heap page
>     predicate locking), not just hash indexes.  Please consider those
>     ideas parked for now.
> 
> 
> OK.  While our potential pseudo-pages are identified as
> "hash_value % some_constant_modulus", real bucket pages are very roughly
> identified as "hash_value % number_of_index_pages".  So, page number is
> adoptive to index size, despite it costs us handling page split. In the 
> same way,
> locking in other index access methods is adoptive to an index size, so
> that should be considered as useful feature which should be present in 
> hash index
> as well.
> 
> ------
> Alexander Korotkov
> Postgres Professional:http://www.postgrespro.com 
> <http://www.postgrespro.com/>
> The Russian Postgres Company

-- 
Teodor Sigaev                      E-mail: teodor@sigaev.ru
                                       WWW: http://www.sigaev.ru/