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 Fri,  5 Jun 2020 14:18:16 +0300 (MSK)
Date: Fri, 5 Jun 2020 11:18:15 +0000
From: Nikita Pettik <korablev@tarantool.org>
Message-ID: <20200605111815.GA26017@tarantool.org>
References: <7407b62139349ee3904a674490a6222b0c960a1c.1591292549.git.korablev@tarantool.org>
 <20200604225215.GB146885@atlas>
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Subject: Re: [Tarantool-patches] [PATCH] vinyl: rotate mem during index
	build on demand
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To: Konstantin Osipov <kostja.osipov@gmail.com>, tarantool-patches@dev.tarantool.org, v.shpilevoy@tarantool.org, alyapunov@tarantool.org

On 05 Jun 01:52, Konstantin Osipov wrote:
> * Nikita Pettik <korablev@tarantool.org> [20/06/04 20:49]:
> > So to get rid of generations mismatch, let's rotate in-memory level
> > after yield on demand.
> 
> Could you please also elaborate why generation mismatch is bad
> here? What does it lead to specifically?

Because right after yield, vy_stmt is allocated using ls region
(in vy_build_insert_stmt()) and inserted into mem. Ls region does
not tolerate non-decreasing ids: otherwise region gc may truncate
data which is still accessible.
 
> 
> -- 
> Konstantin Osipov, Moscow, Russia