RE: index collate

2014-09-11 Thread Zhigang Zhang 

Got it;

Thanks!

Zhigang



-Original Message-
From: Hartmut Holzgraefe [mailto:hart...@skysql.com] 
Sent: Thursday, September 11, 2014 1:44 PM
To: mysql@lists.mysql.com
Subject: Re: index collate

On 09/11/2014 05:55 AM, Zhigang Zhang wrote:

 The “CREATE INDEX Syntax” can not assign a collation.
 
 What collation to use to create a index on a column?

The collation used for an index on a textual column is
the columns collation itself.

You can't choose a different collation for the index,
this would come down to having a functional index
or index on expression as you'd need to apply
CAST() or CONVERT() on the column first to change
the collation.

MySQL doesn't have support for expression based
indexes though ...

-- 
Hartmut Holzgraefe, Principal Support Engineer (EMEA)
SkySQL - The MariaDB Company | http://www.skysql.com/

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Re: MySQL 5.5.33 History list not purging?

2014-09-11 Thread Brad Heller 
So I've done some more digging on this.


   1. Upgraded to MySQL 5.5.37
   2. Made sure we didn't have any old/long running transactions--nothing
   more than a few seconds.
   3. Did a dump/reload in to a new DB and started with an empty history
   list. A few days later, we're back up over 3mil in the list.

We're currently writing about 50MB/s to that machine. Is it possible the
purge thread just...can't keep up for some reason? How can I get better
visibility in to how quickly the purge thread is working vs. how many undo
entries are being put in the thread?

Thanks,


*Brad Heller *| Director of Engineering | Cloudability.com | 541-231-1514 |
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On Sun, Sep 7, 2014 at 2:04 AM, Jesper Wisborg Krogh my...@wisborg.dk
wrote:

 Hi Brad,

  -Original Message-
  From: Brad Heller [mailto:b...@cloudability.com]
  Sent: Sunday, 7 September 2014 03:07
  To: MySQL General List
  Subject: MySQL 5.5.33 History list not purging?
 
  For some reason, the history list isn't purging on one of my masters.
 This is
  causing all kinds of weird issues/behavior with reads. Here's the last 8
 or so
  hours of history list length:
 
  http://i.imgur.com/Q4DEeVi.png
 

 I would start looking for an old transaction. You can use SHOW ENGINE
 INNODB STATUS or the information_schema.INNODB_TRX table to look for that.

 Best regards,
 Jesper Krogh
 MySQL Support



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