Hi,
Is there any example of push-down conditions?
The handler.h/cpp only defined cond_push, cond_pop, but there is no way of
using it.
a > 5 and b > 6 and c > 7.
when to push b > 6 or c >7, when to pop? Does the engine must support
restore the result before cond push.
Thanks!
-----Original Message-----
From: Paul McCullagh [mailto:paul.mccullagh@stripped]
Sent: Tuesday, November 21, 2006 11:36 PM
To: xiao.feng
Cc: Sergei Golubchik; MySQL Internal
Subject: Re: How to get key info of index?
I think only push-down conditions will solve your problem.
The engine API currently only supports basic index searches.
And an index search cannot be used to find "a > 5 and b > 6 and c >
7", even given an index on (a, b, c). The system must search for "a >
5", and then scan the rest of the index, filtering out the other
conditions.
On Nov 21, 2006, at 2:05 PM, xiao.feng wrote:
>>>>> create table abc(a int, b int, c int);
>>> create index idx_abc_all on abc(a, b, c).
>>> select * from abc where a > 5 and b > 6 and c > 7;
>>> I can only get a, but no b and c.
> You say that: because MySQL creates the range 'a > 5' for the above
> query,.
> but these condition, MySQL read a lot of unwanted records from my
> storage engine.
> How to resolve this problem?
> Thanks!
>
>
> ----- Original Message -----
> From: "Sergei Golubchik" <serg@stripped>
> To: "xiao.feng" <xiao.feng@stripped>
> Cc: <internals@stripped>
> Sent: Tuesday, November 21, 2006 7:29 PM
> Subject: Re: How to get key info of index?
>
>
>> Hi!
>>
>> On Nov 17, xiao.feng wrote:
>>> Hi,
>>> How to get key info of index?
>>> create table abc(a int, b int, c int);
>>> create index idx_abc_all on abc(a, b, c).
>>> select * from abc where a > 5 and b > 6 and c > 7;
>>>
>>> int ha_test::read_range_first(const key_range *start_key, const
>>> key_range *end_key, bool eq_range, bool sorted)
>>> how to use start_key and end_key to get the key info for a, b, c.
>>> I can only get a, but no b and c.
>>
>> Right, because MySQL creates the range 'a > 5' for the above
>> query, and
>> you only see this in start_key. If you'll write
>>
>> where a = b and b > 6 and c > 7
>>
>> then you'll see both a and b in start_key but not c.
>>
>> Regards,
>> Sergei
>>
>> --
>> __ ___ ___ ____ __
>> / |/ /_ __/ __/ __ \/ / Sergei Golubchik <serg@stripped>
>> / /|_/ / // /\ \/ /_/ / /__ MySQL AB, Senior Software Developer
>> /_/ /_/\_, /___/\___\_\___/ Kerpen, Germany
>> <___/ www.mysql.com
>
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