Re: How the Planner in PGStrom differs from PostgreSQL?

>  Can u explain this statement "check whether the scan qualifier can be
> executable on GPU device"
>
> What are the scan qualifiers?
>
SELECT * FROM my_table WHERE x > 20 AND memo LIKE '%abc%';
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This is scan qualifier.

> How to determine whether they are device executable or not?
>
If all the function (or function on behalf of operator) are
available to transform GPU source code. Please see codegen.c.

> The cost estimates are entirely based on number of rows and type of scan.
> Then it will be same for both CPU and GPU. How the decision can be made
> for cheaper one comparing CPU and GPU estimates?
>
If Scan path has any scan qualifier, its cost to evaluate depends on
the device type. PG-Strom assumes GPU has larger startup cost but
less cost per tuple. So, GpuScan path is tend to be choosen if number
of rows are relatively large.

Thanks,
--
The PG-Strom Project / NEC OSS Promotion Center
KaiGai Kohei <kaigai@ak.jp.nec.com>