maria-discuss team mailing list archive

[Justin Swanhart <greenlion@xxxxxxxxx>]

You could use Shard-Query (https://mariadb.com/kb/en/library/shard-query/) to process the query in parallel over the partitions.  This will improve the performance of OLAP type queries.

> On Dec 11, 2018, at 5:27 AM, <Rhys.Campbell@xxxxxxxxxxxx> <Rhys.Campbell@xxxxxxxxxxxx> wrote:
> 
> Can you put this is a proc and cycle through the list of partitions? I recall doing this a number of years ago and found this to be much faster than a single query.
>  
> Perhaps profiling the query can throw up some specifics…
>  
> https://mariadb.com/kb/en/library/information-schema-profiling-table/ 
>  
>  
> From: Maria-discuss [mailto:maria-discuss-bounces+rhys.campbell=swisscom.com@xxxxxxxxxxxxxxxxxxx] On Behalf Of Conor Murphy
> Sent: 11 December 2018 01:27
> To: maria-discuss@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Maria-discuss] Large query performance degrade after converting table from MyISAM to InnoDB
>  
> Hi,
>  
> The explain for the MyISAM table is the same as what's given for the InnoDB version
>  
> +------+-------------+------------+-------+---------------+--------+---------+------+-----------+-------+
> | id   | select_type | table      | type  | possible_keys | key    | key_len | ref  | rows      | Extra |
> +------+-------------+------------+-------+---------------+--------+---------+------+-----------+-------+
> |    1 | SIMPLE      | proc_stats | index | NULL          | pidIdx | 2       | NULL | 956763463 |       |
> +------+-------------+------------+-------+---------------+--------+---------+------+-----------+-------+
>  
> I've only done a very basic tuning for InnoDB, i.e. give it a 24GB cache
>  
> innodb-file-per-table=1
> innodb-buffer-pool-size=24G
> innodb_buffer_pool_instances=12
>  
> The table holds time series data and the majority of queries on the table use the time column which allows the partition pruning to operate.However, this particular query is related to a nightly maintenance activity and ends up performing a full scan of the table. But this is the same for MyISAM which takes ~ 6 minutes to perform the query.
>  
> So cause of the ~ 14 hours must be something specific to InnoDB but I've no idea how to drill down to see what the issue with InnoDB is.
>  
> Thanks,
> Conor
>  
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