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Re: Correct parsing of BINLOG 'XXX' with comment inside


Hi Sachin,

On 10/16/2018 03:49 AM, Sachin Setiya wrote:
> Hi Bar!
> On Tue, Sep 11, 2018 at 1:47 PM Alexander Barkov <bar@xxxxxxxxxxx> wrote:
>> Hi Sachin,
>> On 09/10/2018 03:47 PM, Sachin Setia wrote:
>>> Hi Bar,
>>> Currently if we have generated the sql file using mysqlbinlog -v and
>>> if we have big statement binlog
>>> , then mysqlbinlog add comment in between of Binlog 'XXX' statement ,
>>> but unfortunately base64_decode
>>> does not understands it, and it through error since # is not a base64 char
>>> This patches solves this.
>> Note, base64_decode() is used in at least two places:
>> - for the binary log
>> - for the SQL function FROM_BASE64()
>> I don't like that your patch changes the behavior of the SQL function
>> FROM_BASE64(). It should not recognize any '#' inside the base64 data
>> as comments.
> Right , So I have creates a flag MY_BASE64_DECODE_ALLOW_COMMENTS it is
> kind of similar to as MY_BASE64_DECODE_ALLOW_MULTIPLE_CHUNKS flag is used
> So no impact on FROM_BASE64
>> So perhaps this should be fixed in some other place, not in base64_decode().
>> I checked the output of these commands:
>> ./bin/mysqlbinlog      ./data/retsina-bin.000003
>> ./bin/mysqlbinlog -vvv ./data/retsina-bin.000003
>> It looks suspicious for me.
>> Can you please remind why mysqlbinlog prints multiple base64 chunks
>> inside the same BINLOG statement?
> It is beacuse if we have long row we can have more then one

Do you know where in the code the server decides to end
the current chunk and start a new one?

Is there some limit (in bytes, or in number or records)?

>> From my understanding, it is "mysqlbinlog -vvv" who should be fixed
>> to print good base64 data inside the string literal that follows the
>> BINLOG keyword.
>> At least  the additional comments printed by -vvv should be outside of
>> the BINLOG statement (presumably before), not inside.
> Idk , this can be lot of work , plus it will slow mysqlbinlog also ,
> And I think with new solution FROM_BASE64 behavior is not changed
> I have added test for FROM_BASE64
> #No change in BASE64_FROM behaviour
> #Comment 344
> #
> aWE=') AS 'Output';
> this will generate Maria in earlier patch which is wrong , with new
> patch it gives NULL

If we really go this way, I suggest to cover all these scenarios too:

SELECT FROM_BASE64('TWFyaWE=# comment1');
SELECT FROM_BASE64('TWFyaWE=\n# comment1');
SELECT FROM_BASE64('TWFyaWE=\n# comment1\nTWFyaWE=');
SELECT FROM_BASE64('TWFyaWE=\n# comment1\nTWFyaWE=\n# comment2\n');

They all should give NULL.

>> Thanks.
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