sábado, 25 de outubro de 2014

MariaDB 10.1.1: system variables and their metadata


I don’t think it’ll surprise anybody if I say that MariaDB or MySQL server knows a lot more about server system variables, then just their values. Indeed, every variable can be session or global only, read-only or writable, it has an associated help text (that is printed on mysqld --help --verbose), certain variables only accept… Continue reading

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sexta-feira, 24 de outubro de 2014

Returning Column Metadata for a Specific Table


Do you ever have one of those questions you just can't find a good solution to through an Internet search?
The SQL Server Community uses Twitter quite efficiently—and just yesterday, through the use of the #sqlhelp hashtag—one community member had their question answered, and I came up with this article as a result.

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ERROR "This operation is not defined for system tables" WHEN CREATING A PRIMARY KEY ON FIREBIRD 3

I can understand that some new functionalities might not work on a beta/alpha release, but this is related to a primery key creation, so I can't see a plausable reason for it not to work.

Im trying to run a simple script, creating a table with a primary key.

     oid INT NOT NULL, 
     CONSTRAINT pk_oids PRIMARY KEY(oid) 

and I get this

Cannot commit transaction:
This operation is not defined for system tables.
unsuccessful metadata update.
cannot create index PK_OIDS.

I created a discussion on Yahoo Firebird Group, but apparently it was delete, because you can ask anything in the Firebird Group, EXCEPT ask about problemas in ALPHA/BETA releases. What is that all about?

No wonder Firebird is almost invisible in the database arena these days..

Defragmenting unused space on InnoDB tablespace


Introduction When you e.g. delete rows, these rows are just marked as deleted not really physically deleted from indexes and free space introduced is not returned to operating system for later reuse. Purge thread will physically delete index keys and rows, but still free space introduced is not returned to operating system and this operation… Continue reading

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quinta-feira, 23 de outubro de 2014

Top 5 Things to Look for in a Disaster-Recovery-as-a-Service (DRaaS) Provider


For SQL Server users who can't afford to build, configure, test, and maintain an effective SQL Server disaster recovery plan (DRP), disaster recovery as a service (DRaaS) can be a great option.

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Firebird 3 Beta 1 Unofficial Installers for Windows and Linux are available

Firebird 3 is on its track to release: the first Beta version of source code was tagged, and now Firebird core developers work on Beta 2, with intention to release final Firebird 3 in the beginning of 2015. 

How to ensure that Firebird 3 will be stable and reliable? How to make it happen earlier? The answer for these questions is: intensive beta-testing with wide community support.

To start effective beta-testing earlier and to supply Firebird developers with convinient path to Firebird 3 we started Firebird 3 Launch Campaign (www.firebird3.com).  It has 3 parts:

1) Firebird 3 distributives, materials and documentation, with focus on Firebird 3 new features, configuration tips and tricks, performance testing, and, of course, beta-testing.  

2) Banners for Firebird 3. To support Firebird 3 Launch Campaign, simply put Firebird 3 banner  to your blog/web-site, and point them to www.firebird3.com

3) Social activity: starting with simple posts and «likes», then we will continue with contests and special prizes. Join Firebird in Facebook  (https://www.facebook.com/FirebirdSQL ) and LinkedIn (https://www.linkedin.com/groups?gid=2078215) to be part of the action!

We believe that Firebird 3 will become the best version of Firebird ever, and to encourage you and all Firebird developers we prepared a lot of very interesting materials for Firebird Launch Campaign.

Stay tuned for Firebird 3 news!

Check out my new book on MariaDB http://www.amazon.com/dp/B00MQC06HC

Monitoring progress and temporal memory usage of Online DDL in InnoDB


Introduction Online DDL is a new feature in MariaDB 10.0. Online DDL is processed through below 4 tasks in sequence. InnoDB::ha_prepare_inplace_alter_table(..) InnoDB::ha_inplace_alter_table(..) InnoDB::ha_commit_inplace_alter_table(..) mysql_rename_table(..) InnoDB storage engine allocates temporal memory buffer for transaction logging in phase 1 where row changes during this phase are logged. Size of this buffer is at start sort_buffer_size and it… Continue reading

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quarta-feira, 22 de outubro de 2014

MariaDB 10.1.1: FLUSH and SHOW for plugins


One of the most popular plugin types both in MariaDB and MySQL is INFORMATION_SCHEMA plugin type. INFORMATION_SCHEMA plugins add new tables to the INFORMATION_SCHEMA. There are lots of INFORMATION_SCHEMA plugins, because they can be used to show just anything to the user and are very easy to write. MariaDB 10.1.1 comes with nine INFORMATION_SCHEMA plugin:… Continue reading

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PASS Summit Announcement: Day 2, Women in Technology Keynotes


Kelsey Levitt
Recently announced are two new keynote speakers for PASS 2014. The Day 2 keynote will be presented by Dr. Rimma Nehme, and the keynote speaker for the Women in Technology Luncheon will be Kimberly Bryant.

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NULLs and SQL SERVER... details matter!

While refactoring a function made  by a developer , I came across a situation where the COALESCE was not helping to prevent null values​​. In case it was an assignment of value to a variable based on a query.

Observe the test code below:

     codigo INT 

DECLARE @codigo INT; 

SELECT @codigo = COALESCE(codigo, 0) 
FROM   #teste 

SELECT @codigo AS [Retornando NULO] 

DROP TABLE #teste 

If you run the above code, notice that the result is null, even using the coalesce function. In case, the developer decided issue by adding a check with IF testing checking if the variable is null.

This is not wrong, but I think we should reduce the flow of unnecessary code. We can work around the problem by adding the default value in the variable declaration. Thus, if the query returns nothing, the variable retains the original value.

     codigo INT 

VALUES      (1) 

DECLARE @codigo2 INT = 0; 

SELECT @codigo2 = COALESCE(codigo, 0) 
FROM   #teste 

SELECT @codigo2 AS [Retornando ZERO] 


Check out my new book on MariaDB http://www.amazon.com/dp/B00MQC06HC