phoenix-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Pham Phuong Tu <tuphamphu...@gmail.com>
Subject Re: Phoenix performance efficient problem?
Date Tue, 03 Jun 2014 04:43:52 GMT
Hi Vladimir Rodionov,

You are righ when explain the selectivity when we do not use index . But
when use index, this query fetch, count with only 300 row, it take 10
second !





2014-06-03 11:35 GMT+07:00 Vladimir Rodionov <vladrodionov@gmail.com>:

> First query selectivity is 1:1000 = 0.1%
> Second is 300/1000 = 30%
>
> This pretty much explains performance difference.
>
> Try :
> select count(*) from test where int_1 > 999
>
>
> On Mon, Jun 2, 2014 at 9:20 PM, Pham Phuong Tu <tuphamphuong@gmail.com>
> wrote:
>
>> HI guys,
>>
>> I have a test table with 20M rows, one row have 2 column type integer, 1
>> column have index, other dont't have. Value of integer column is random
>> value from 0 to 1000.
>>
>> Run query with equal condition below, query in column with index is much
>> faster.
>> "select count(*) from test where int_1 = 100;"
>> (0.084 seconds vs 15.221 seconds) => > 150x faster
>>
>> But when run a range query, query in column with index is not much faster.
>> "select count(*) from test where int_1 > 700;"
>> (7.852 seconds vs 12.889 seconds) => > 0.5x faster
>>
>> Should index have to optimize data organizaion or algorithm to increase
>> performance ?
>>
>> Thanks a lot.
>>
>>
>

Mime
View raw message