Comment 3 for bug 721176

Alexey,

What I mean is we need a test case in Percona Server 5.1 which would cover
when these values are different.
In this case I assume such test case would have been ported to Percona
Server 5.5 and would have broken when
patch was not ported correctly.

On Fri, Feb 18, 2011 at 10:52 AM, Alexey Kopytov <<email address hidden>
> wrote:

> Peter,
>
> In 5.5 Rows_read and Rows_sent are always the same simply because the
> same value is used for both due to a bug in porting slow_extended.
>
> I'm not sure how to demonstrate "always", but here's just one example:
>
> create table t1(a int);
> insert into t1 values(1),(2),(3),(4);
> set @@min_examined_row_limit=1;
>
> select * from t1;
> # Query_time: 0.000413 Lock_time: 0.000152 Rows_sent: 4 Rows_examined: 4
> Rows_affected: 0 Rows_read: 4
> select * from t1 where a=1;
> # Query_time: 0.000607 Lock_time: 0.000299 Rows_sent: 1 Rows_examined: 4
> Rows_affected: 0 Rows_read: 1
> select * from t1 where a=5;
> # Query_time: 0.000460 Lock_time: 0.000170 Rows_sent: 0 Rows_examined: 4
> Rows_affected: 0 Rows_read: 0
>
> Which raises 2 questions:
>
> 1. Why is Rows_read different in all three cases?
> 2. What is Rows_read really supposed to mean?
>
> --
> You received this bug notification because you are a member of Percona
> developers, which is the registrant for Percona Server.
> https://bugs.launchpad.net/bugs/721176
>
> Title:
> slow_extended in 5.5 always shows identical values for Rows_sent and
> Rows_read
>
> Status in Percona Server with XtraDB:
> New
>
> Bug description:
> slow_extended in 5.5 uses the same variable (thd->sent_row_count) to
> print both Rows_sent and Rows_read in the extended slow query log
> stats. This can be verified by examining MYSQL_QUERY_LOG::write() in
> log.cc.
>
> The bug was introduced when porting slow_extended.patch to 5.5.
>
> On the other hand, I don't understand the meaning of Rows_read. What
> information is it supposed to reflect? Should we really have it in the
> slow log?
>

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