On 2020/02/01 16:05, Kasahara Tatsuhito wrote:
On Thu, Jan 30, 2020 at 1:49 PM Kyotaro Horiguchi
<horikyota....@gmail.com> wrote:
At Thu, 30 Jan 2020 13:30:56 +0900, Kasahara Tatsuhito
<kasahara.tatsuh...@gmail.com> wrote in
TID scan : yes , seq_scan, <none> , <none>
Here is wrong, because TID scan came to have SO_TYPE_SEQSCAN flags
from commit 147e3722f7.
It is reflectings the discussion below, which means TID scan doesn't
have corresponding SO_TYPE_ value. Currently it is setting
SO_TYPE_SEQSCAN by accedent.
Ah, sorry I misunderstood..
Upon further investigation, the SO_TYPE_SEQSCAN flag was also used at
heap_beginscan() to determine whether a predicate lock was taken on
the entire relation.
if (scan->rs_base.rs_flags & (SO_TYPE_SEQSCAN | SO_TYPE_SAMPLESCAN))
{
/*
* Ensure a missing snapshot is noticed reliably, even if the
* isolation mode means predicate locking isn't performed (and
* therefore the snapshot isn't used here).
*/
Assert(snapshot);
PredicateLockRelation(relation, snapshot);
}
Therefore, it can not simply remove the SO_TYPE_SEQSCAN flag from a TID scan.
To keep the old behavior, I think it would be better to add a new
SO_TYPE_TIDSCAN flag and take a predicate lock on the entire relation.
But in the old behavior, PredicateLockRelation() was not called in TidScan case
because its flag was not SO_TYPE_SEQSCAN. No?
Regards,
--
Fujii Masao
NTT DATA CORPORATION
Advanced Platform Technology Group
Research and Development Headquarters
