RE: [PATCH] pg_stat_toast v0.3

Dear Gunnar,

> The attached v0.3 includes
> * columns "storagemethod" and "compressmethod" added as per Hayato
> Kuroda's suggestion

I prefer your implementation that referring another system view.

> * gathering timing information

Here is a minor comment:
I'm not sure when we should start to measure time.
If you want to record time spent for compressing, toast_compress_datum() should be
sandwiched by INSTR_TIME_SET_CURRENT() and caclurate the time duration.
Currently time_spent is calcurated in the pgstat_report_toast_activity(),
but this have a systematic error.
If you want to record time spent for inserting/updating, however,
I think we should start measuring at the upper layer, maybe heap_toast_insert_or_update().

> Any hints on how to write meaningful tests would be much appreciated!
> I.e., will a test

I searched hints from PG sources, and I thought that modules/ subdirectory can be used.
Following is the example:
https://github.com/postgres/postgres/tree/master/src/test/modules/commit_ts

I attached a patch to create a new test. Could you rewrite the sql and the output file?

Best Regards,
Hayato Kuroda
FUJITSU LIMITED