On 14/11/11 12:20, Robert Haas wrote:
> On Mon, Nov 14, 2011 at 8:25 AM, Rudyar<rudyar.cortes@gmail.com> wrote:
>> the hybrid hash join algorithm implemented in the current version of
>> PostgreSQL has any kind of optimization
>> for star join queries for Data Warehouse model?
> Not really. As much as possible, we try to make the query optimizer a
> general-purpose tool that can handle any query you happen to throw at
> it, rather than putting in special-purpose hacks to cater to specific
> types of queries. I'm not aware of anything in particular that we
> could do to better optimize the star-join case than what we do for any
> other query.
>
> Now, one thing that was discussed a year or two ago was the
> possibility of considering join algorithms that can handle more than
> two tables at a time. Currently, we don't do that, so a four-way join
> will be implemented either by joining two tables, then the other two
> tables, and then the results of those; or more commonly by joining two
> tables, joining the results to a third table, and then joining those
> results to the final table. Due to the pipelined nature of our
> executor, this works pretty well, but it's possible that there are
> better algorithms out there.
>
Thanks Robert,
I'm a new programmer in postgreSQL source code and I working in my tesis
project about that optimizations to HHJ algorithm.
I think so is very useful that optimizer recognize one star join and
apply this optimizations..
For example, SQL Server and Oracle databases implements star join query
optimizations for OLAP queries in DW.
How can contribute with my tesis project to postreSQL source code?
Regards.
--
Rudyar Cortés.
Estudiante de Ingeniería Civil Informática
Universidad Técnica Federico Santa María.