On Wed, Aug 30, 2017 at 10:03 PM, 유상지 <y0...@naver.com> wrote:
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>
> I want to get help with Postgresql.
>
> I investigated that Postgresql could be rather fast in an environment
> using a secondary index. but It came up with different results on benckmark.
>
> The database I compared was mariadb, and the benchmark tool was sysbench
> 1.0.8 with the postgresql driver.
>
> Server environment: vmware, Ubuntu 17.04, processor: 4, RAM: 4 GB,
> Harddisk: 40 GB, Mariadb (v10.3), PostgreSQL (v9.6.4)
>
>
>
> The created sysbench progress statement is as follows.
>
> Sysbench /usr/share/sysbench/oltp_read_only.lua --db-driver = mysql
> --mysql-host = 127.0.0.1 --mysql-port = 3306 --mysql-user = root
> --mysql-password = ajdajddl75 - Mysql-db = sysbench --tables = 3
> --table_size = 100000 --report-interval = 10 --secondary = on --time = 60
>
>
>
> Used options
>
> Select only, Num of threads = 1, num of tables = 3, table-size = 100000
> and Table-size = 1000000, secondary index select instead of primary key.
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> My hypothesis was that selecting by secondary index in postgresql is
> faster than in Mariadb. However, the results depend on table size.
>
>
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> Postgresql was faster than Mariadb when the table size was 1000000, but
> slower at 100000.
>
>
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> Cluster secondary indexes were faster than those without cluster indexes
> in pg, but slower than mariadb.
>
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> I'd like to see the difference in architecture rather than optimization,
> so every benchmark executed with default options except for clustered index.
>
> I wonder if there are any settings I missed.
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> I would be very pleased if someone could explain why these results came up.
>
>Postgresql was faster than Mariadb when the table size was 1000000, but
slower at 100000.
You made a general statement, but you left out a lot of important
information.
A. Did you do an ANALYZE table_name BEFORE running your test?
B. Did you verify the index was being used with EXPLAIN your_query?
C. What was the exact query you used?
D. Most important, what is the structure of the table and index?
E. How much system memory is there?
F. In postgresql.conf What are the settings for
1. shared_memory
2. work_memory
3. All Planner Cost Constants values, All Genetic Query Optimizer values
--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.
