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 Mon, 22 Jun 2020 23:21:09 +0300 (MSK)
Date: Mon, 22 Jun 2020 20:21:08 +0000
From: Nikita Pettik <korablev@tarantool.org>
Message-ID: <20200622202108.GA32744@tarantool.org>
References: <cover.1586808463.git.korablev@tarantool.org>
 <0bdc1b5e-82b4-2e24-ad06-26587b007742@tarantool.org>
 <20200522024206.GA24698@tarantool.org>
 <9820269f-95a1-4d11-c08f-c2dd2b642740@tarantool.org>
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In-Reply-To: <9820269f-95a1-4d11-c08f-c2dd2b642740@tarantool.org>
Subject: Re: [Tarantool-patches] [PATCH 0/2] Validate result of upserts
 squash & skip invalid upserts which can't be applied
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To: Aleksandr Lyapunov <alyapunov@tarantool.org>
Cc: tarantool-patches@dev.tarantool.org, Vladislav Shpilevoy <v.shpilevoy@tarantool.org>

On 22 Jun 17:13, Aleksandr Lyapunov wrote:
> HI, thanks for the patch! see one comment below
> 
> On 5/22/20 5:42 AM, Nikita Pettik wrote:
> > 
> > diff --git a/src/box/vinyl.c b/src/box/vinyl.c
> > index 55a4c8fb7..b39e3b9d8 100644
> > --- a/src/box/vinyl.c
> > +++ b/src/box/vinyl.c
> > @@ -3539,10 +3539,21 @@ vy_squash_process(struct vy_squash *squash)
> >                  if (vy_tuple_compare(result, mem_stmt, lsm->cmp_def) != 0 ||
> >                      vy_stmt_type(mem_stmt) != IPROTO_UPSERT)
> >                          break;
> > -               assert(vy_stmt_lsn(mem_stmt) >= MAX_LSN);
> > -               vy_stmt_set_n_upserts((struct tuple *)mem_stmt, n_upserts);
> > -               if (n_upserts <= VY_UPSERT_THRESHOLD)
> > -                       ++n_upserts;
> > +               /*
> > +                * Upsert was not applied in vy_history_apply(),
> > +                * but it still resides in tree memory. Ignore
> > +                * such statements and do not account them while
> > +                * counting upserts. Otherwise invalid upserts will
> > +                * get stack and won't allow other upserts to squash.
> > +                */
> > +               if (vy_stmt_lsn(mem_stmt) >= MAX_LSN) {
> > +                       vy_stmt_set_n_upserts((struct tuple *) mem_stmt,
> > +                                             n_upserts);
> > +                       if (n_upserts <= VY_UPSERT_THRESHOLD)
> > +                               ++n_upserts;
> > +               } else {
> > +                       vy_stmt_set_n_upserts((struct tuple *) mem_stmt, 0);
> > +               }
> I bet we should just remove assert here. If mem_stmt have
> a valid LSN now - it is a valid statement. The first of them must
> have n_upserts=0, the second - 1 etc, and n_upsert of following
> prepared statements must continue the sequence.

What is the point of keeping counting n_upserts for upserts
which can't be squashed? For sure we can simply remove assertion,
but then after accumulating more than 128 upserts which can't
be applied, vy_squash_process won't be called till dump...