From: AugustQ
Date: February 27 2011 7:54pm
Subject: condition pushdown
List-Archive: http://lists.mysql.com/internals/38254
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Hi,

how can I enable condition pushdown?

This is my first question here on this list. I'm working as a
software-developer for quite some time and currently I am working in a
DWH-project here in Germany.

I found these sources: mysql-5.5.0-m2
and got it to compile and work here on my machine (Ubuntu 64bit).
After some reading (books from Hutchings/Golubchik and Pachev) I decided
to play a bit with storage engines, so I wrote my tiny storage engines
(which work, so the basics are understood, at least in parts).

The next topic I wanted to play with is condition pushdown but I had no
luck until now.
In mysql I can do
    set engine_condition_pushdown=1
and got a result OK. 
When I enter 
    explain select * from prob_alt where rv_nr = '12345678'\G
I can only see 'using where', nothing more.

I've set a breakpoint to the following piece of code:

    const COND * ha_dbf::cond_push(const COND *cond)
    {
        myCond = (COND *)cond;
        return cond;
    };

Looking at the cond-var I do not see anything meaningful, mostly
NULL-Ptrs.

I assume that condition pushdown is disabled by default. So what do I
have to do to enable it?

Should I use another version of MySQL/MariaDB instead?

Thanks 
AugustQ