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Date: Thu, 20 Feb 2020 22:58:21 +0300
From: Nikita Pettik <korablev@tarantool.org>
Message-ID: <20200220195821.GE95807@tarantool.org>
References: <4f7cb05d8161597c0e58520b75af04167ce0b5e6.1581580784.git.imeevma@gmail.com>
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In-Reply-To: <4f7cb05d8161597c0e58520b75af04167ce0b5e6.1581580784.git.imeevma@gmail.com>
Subject: Re: [Tarantool-patches] [PATCH v2 1/1] sql: limit blob size during
	CAST AS INTEGER
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To: imeevma@tarantool.org
Cc: tarantool-patches@dev.tarantool.org

On 13 Feb 11:16, imeevma@tarantool.org wrote:
> >> +test:do_execsql_test(
> >> +    "cast-6.1",
> >> +    [[
> >> +        CREATE TABLE t (a VARBINARY PRIMARY KEY);
> >> +        INSERT INTO t VALUES (X'33'), (X'372020202020');
> >> +        SELECT a, CAST(a AS NUMBER), CAST(a AS INTEGER), CAST(a AS UNSIGNED) FROM t;
> >> +        DROP TABLE t;
> >> +    ]], {
> >> +        -- <cast-6.1>
> >> +        '3', 3, 3, 3, '7     ', 7, 7, 7
> >> +        -- </cast-6.1>
> >> +    })
> >> +
> >> +test:do_execsql_test(
> >> +    "cast-6.2",
> >> +    [[
> >> +        CREATE TABLE t (a VARBINARY PRIMARY KEY, i INT);
> >> +        INSERT INTO t VALUES (X'33', 1);
> >> +        SELECT a, CAST(a AS NUMBER), CAST(a AS INTEGER), CAST(a AS UNSIGNED) FROM t;
> >> +        DROP TABLE t;
> >
> > What's the (in functional sense) difference between 6.1 and 6.2?
> >
> True, in this test it isn't obvious what it should show. I fixed
> the test. I made this test to show that the '\0' at the end of the
> BLOB is important. One possible way to solve this problem was to
> limit the length of the decoded BLOB (without copying and adding
> '\0'), but this could lead to an incorrect result of this test.
> I mean this:
> 
> tarantool> CREATE TABLE t (a VARBINARY PRIMARY KEY, i INT) WITH ENGINE = 'vinyl';
> ---
> - row_count: 1
> ...
> 
> tarantool> INSERT INTO t VALUES (X'33', 0x33);
> ---
> - row_count: 1
> ...

So now you insert 0x33 instead of 1 to integer field. But how does it
affect test? I failed to understand. In both cases you fetch and operate
on blob, meanwhile integer field doesn't seem to be involved.

> 
> tarantool> SELECT a, CAST(a AS NUMBER), CAST(a AS INTEGER), CAST(a AS UNSIGNED) FROM t;
> ---
> - metadata:
>   - name: A
>     type: varbinary
>   - name: CAST(a AS NUMBER)
>     type: number
>   - name: CAST(a AS INTEGER)
>     type: integer
>   - name: CAST(a AS UNSIGNED)
>     type: unsigned
>   rows:
>   - ['3', 33, 33, 33]
> ...
> 
> +--
> +-- In some cases, the absence of '\0' could lead to an incorrect
> +-- result. Make sure this does not happen now.
> +--
>  test:do_execsql_test(
>      "cast-6.2",
>      [[
>          CREATE TABLE t (a VARBINARY PRIMARY KEY, i INT);
> -        INSERT INTO t VALUES (X'33', 1);
> +        INSERT INTO t VALUES (X'33', 0x33);
>          SELECT a, CAST(a AS NUMBER), CAST(a AS INTEGER), CAST(a AS UNSIGNED) FROM t;
>          DROP TABLE t;
>      ]], {
>