RE: Parallel Inserts in CREATE TABLE AS

From: houzj.fnst@fujitsu.com <houzj.fnst@fujitsu.com>
> +        /*
> +         * We don't need to skip contacting FSM while inserting tuples
> for
> +         * parallel mode, while extending the relations, workers
> instead of
> +         * blocking on a page while another worker is inserting, can
> check the
> +         * FSM for another page that can accommodate the tuples.
> This results
> +         * in major benefit for parallel inserts.
> +         */
> +        myState->ti_options = 0;
> 
> I am not quite sure that disabling the " SKIP FSM " in parallel worker will bring
> performance gain.
> In my test environment, if I change this code to use option "
> TABLE_INSERT_SKIP_FSM ", then there
> seems no performance degradation.

+1, probably.

Does the code comment represent the situation like this?

1. Worker 1 is inserting into page 1.

2. Worker 2 tries to insert into page 1, but cannot acquire the buffer content lock of page 1 because worker 1 holds
it.

3. Worker 2 looks up FSM to find a page with enough free space.

But isn't FSM still empty during CTAS?



Regards
Takayuki Tsunakawa