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From: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
To: Serge Petrenko <sergepetrenko@tarantool.org>, gorcunov@gmail.com
Cc: tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH v3 2/2] replication: append NOP as the last tx row
Date: Thu, 2 Jul 2020 22:30:00 +0200	[thread overview]
Message-ID: <112b0dfc-017d-f3ac-f1eb-cf6291f3d585@tarantool.org> (raw)
In-Reply-To: <106b9cbcf8577d6e3afbde57b15bc11d366c108e.1593696889.git.sergepetrenko@tarantool.org>

Hi! Thanks for the patch!

See 3 comments below.

> diff --git a/src/box/txn.c b/src/box/txn.c
> index 123520166..9793109f3 100644
> --- a/src/box/txn.c
> +++ b/src/box/txn.c
> @@ -517,6 +519,25 @@ txn_journal_entry_new(struct txn *txn)
>  	assert(remote_row == req->rows + txn->n_applier_rows);
>  	assert(local_row == remote_row + txn->n_new_rows);
>  
> +	/*
> +	 * Append a dummy NOP statement to preserve replication tx
> +	 * boundaries when the last tx row is a local one.
> +	 */
> +	if (txn->n_local_rows > 0 && txn->n_local_rows != txn->n_new_rows &&

1. Why do you need 'txn->n_local_rows != txn->n_new_rows' check?
Looks like local rows are always in the end. So if their count > 0,
you can look at *(local_row - 1) without any other checks, no?

Btw, I just noticed, that we already reorder rows - regardless of
what was the order of their appliance, txn_journal_entry_new()
anyway moves all remote rows first, and local rows second. This looks
like the same problem as I was talking about, when we discussed the
local reorder, and gave a FOREIGN KEY example.

It means it is already broken, in theory. And perhaps that should be
changed.

If we consider it not broken, then why can't we put local rows first,
and remote rows second? Then we don't need NOP here.

> +	    (*(local_row - 1))->group_id == GROUP_LOCAL) {
> +		size_t size;
> +		*local_row = region_alloc_object(&txn->region,
> +						 typeof(**local_row), &size);
> +		if (*local_row == NULL) {
> +			diag_set(OutOfMemory, size, "region_alloc_object", "row");

2. Out of 80.

> +			return NULL;
> +		}
> +		memset(*local_row, 0, sizeof(**local_row));
> +		(*local_row)->type = IPROTO_NOP;
> +		(*local_row)->group_id = GROUP_DEFAULT;
> +	} else
> +		--req->n_rows;

3. Lets add {} to the 'else' branch. To be consistent with the 'if'
branch.

  parent reply	other threads:[~2020-07-02 20:30 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-02 13:39 [Tarantool-patches] [PATCH v3 0/2] fix replication tx boundaries after local space rework Serge Petrenko
2020-07-02 13:39 ` [Tarantool-patches] [PATCH v3 1/2] wal: fix tx boundaries Serge Petrenko
2020-07-02 13:39 ` [Tarantool-patches] [PATCH v3 2/2] replication: append NOP as the last tx row Serge Petrenko
2020-07-02 14:35   ` Cyrill Gorcunov
2020-07-02 14:49     ` Cyrill Gorcunov
2020-07-02 15:37   ` Cyrill Gorcunov
2020-07-02 20:30   ` Vladislav Shpilevoy [this message]
2020-07-03 11:24     ` Serge Petrenko
2020-07-03 21:29       ` Vladislav Shpilevoy
2020-07-04 17:25         ` Serge Petrenko
2020-07-06  6:48           ` Vladislav Shpilevoy
2020-07-06  7:47 ` [Tarantool-patches] [PATCH v3 0/2] fix replication tx boundaries after local space rework Kirill Yukhin

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