Re: SQL/MED estimated time of arrival?

On Wed, 03 Nov 2010 13:32:18 -0700
Eric Davies <eric(at)barrodale(dot)com> wrote:
> On Informix, we were able to take advantage of the VTI (Virtual Table
> Interface) feature to support "table" scans and indexing. (See
> http://www.ibm.com/developerworks/data/zones/informix/library/techarticle/db_vti.html
> .) Do you have any idea of how long it will be before SQL/MED on
> PostgreSQL will be available, and perhaps how similar it will be to
> Informix VTI?

SQL/MED is now under discussion/development for PostgreSQL 9.1, and
9.1 would be released one year after 9.0, maybe around Sep 2011? For
detail of release schedule, please see the development plan of
PostgreSQL 9.1.

http://wiki.postgresql.org/wiki/PostgreSQL_9.1_Development_Plan

I looked into VTI documents you've pointed. ISTM that VTI and SQL/MED
would have a lot of common ideas, and most of VTI items would be able
to be mapped to one of SQL/MED items, except features about updating
data and indexing.

For example:

* PRIMARY ACCESS_METHOD -> HANDLER of FOREIGN DATA WRAPPER
* am_scancost() -> FdwRoutine.EstimateCosts()
* am_open() -> FdwRoutine.Open()
* am_beginscan() -> first call of FdwRoutine.Iterate()?
* am_getnext() -> FdwRoutine.Iterate()
* am_rescan() -> FdwRoutine.ReOpen()
* am_close() -> FdwRoutine.Close()
* Table descriptor -> Relation, Form_pg_class
* Qual descriptor -> PlanState.qual

I hope the summary of SQL/MED described in wiki page helps you.

http://wiki.postgresql.org/wiki/SQL/MED

Any comments and questions are welcome.

Regards,
--
Shigeru Hanada