Re: Tid scan increments value of pg_stat_all_tables.seq_scan. (but not seq_tup_read)

Hi,

On Thu, Feb 6, 2020 at 11:01 PM Masahiko Sawada
<masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
>
> On Thu, 6 Feb 2020 at 19:12, Kasahara Tatsuhito
> <kasahara(dot)tatsuhito(at)gmail(dot)com> wrote:
> I've tested predicate locking including promotion cases with v3 patch
> and it works fine.
>
> +table_beginscan_tid(Relation rel, Snapshot snapshot,
> + int nkeys, struct ScanKeyData *key)
> +{
> + uint32 flags = SO_ALLOW_STRAT | SO_ALLOW_SYNC | SO_ALLOW_PAGEMODE;
>
> IIUC setting SO_ALLOW_STRAT, SO_ALLOW_SYNC and SO_ALLOW_PAGEMODE has
> no meaning during tid scan. I think v11 also should be the same.
Thanks for your check, and useful advise.
I was wondering if I should keep these flags, but I confirmed that I
can remove these from TidScan's flags.

> Why did you remove SO_TYPE_TIDSCAN from the previous version patch? I
> think it's better to add it and then we can set only SO_TYPE_TIDSCAN
> to the scan option of tid scan.
Because, currently SO_TYPE_TIDSCAN is not used anywhere.
So I thought it might be better to avoid adding a new flag.
However, as you said, this flag may be useful for the future tid scan
feature (like [1])

Attach v4 patch. I re-added SO_TYPE_TIDSCAN to ScanOptions and
table_beginscan_tid.
And I remove unnecessary SO_ALLOW_* flags.

Best regards,

[1]
https://www.postgresql.org/message-id/flat/CAKJS1f-%2BJJpm6B_NThUWzFv4007zAjObBXX1CBHE_bH9nOAvSw%40mail.gmail.com#1ae648acdc2df930b19218b6026135d3

--
Tatsuhito Kasahara
kasahara.tatsuhito _at_ gmail.com