maria-discuss team mailing list archive

[Roberto Spadim <roberto@xxxxxxxxxxxxx>]

yeap

at optimizer part of mariadb, is there some check about
clustered/nonclustered/rtree/hash index to select best index or not?

2015-06-22 23:45 GMT-03:00 Justin Swanhart <greenlion@xxxxxxxxx>:

> you are probably thinking of b-trees which are unbalanced.  b+tree is
> o(log(n)) based on depth of tree and you always have to go to bottom to get
> leaf.
>
> On Mon, Jun 22, 2015 at 7:44 PM, Justin Swanhart <greenlion@xxxxxxxxx>
> wrote:
>
>> No, you have to look in the leaf!
>>
>> On Mon, Jun 22, 2015 at 7:43 PM, Roberto Spadim <roberto@xxxxxxxxxxxxx>
>> wrote:
>>
>>> yeap, i just want know if the unique allow stop the conquer at first
>>> result (unique key) or if it continue (non unique key)
>>>
>>> 2015-06-22 23:42 GMT-03:00 Justin Swanhart <greenlion@xxxxxxxxx>:
>>>
>>>> Hi,
>>>>
>>>> b+tree search is binary search, which is divide and conquer.  Saving
>>>> scanning a key is like sneezing in a hurricane, you still are o(log(n)) in.
>>>>
>>>> On Mon, Jun 22, 2015 at 7:39 PM, Justin Swanhart <greenlion@xxxxxxxxx>
>>>> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> If you do a code inspection you will find that uniqueness is checked
>>>>> on insertion, and the database cares not about it after that.
>>>>>
>>>>> --Justin
>>>>>
>>>>> On Mon, Jun 22, 2015 at 7:20 PM, Roberto Spadim <roberto@xxxxxxxxxxxxx
>>>>> > wrote:
>>>>>
>>>>>> and there's optimization with this flag? i see that equal could be
>>>>>> optimized cause if we found 1 row we can return to user that row and stop
>>>>>> select
>>>>>>
>>>>>> in other words, if i see a index with primary key or unique columns,
>>>>>> could i change the index to unique and get some kind of performace? today i
>>>>>> think not ,cause unique key check if it's really unique (for example at
>>>>>> insert/update/replace), i'm wrong?
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> Roberto Spadim
>>> SPAEmpresarial - Software ERP
>>> Eng. Automação e Controle
>>>
>>
>>
>


-- 
Roberto Spadim
SPAEmpresarial - Software ERP
Eng. Automação e Controle