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Displaying posts with tag: csv (reset)
Tech Messages | 2013-03-10

A special extended edition of Tech Messages for 2013-03-07 through 2013-03-10:

Two Cons against NoSQL. Part I.

Two cons against NoSQL data stores read like this: 1. It’s very hard to move data out from one NoSQL to some other system, even other NoSQL. There is a very hard lock in when it comes to NoSQL. If you ever have to move to another database, you have basically to re-implement a lot [...]

Building MariaDB 5.1 on Windows

Recently, I found myself needing MariaDB 5.1.60 for Windows for some testing purposes. Therefore, I needed to build it from source. I ended up using what I’d call a “blend” of the commands listed in this “how-to” and the readme file INSTALL-WIN-SOURCE, so I thought I’d post those steps.

  1. Download 5.1.60 MariaDB source from here.
  2. cd C:\mariadb-5.1
    
  3. win\configure.js
    
  4. cmake .
    
  5. VS: File -> Open -> Solution -> MySql.sln
  6. VS: Build -> Build Solution
  7. VS: Right-click “PACKAGE” -> Build (in “Solution Explorer” View)

That’s it.

Let’s fire it up:

MariaDB> select version(); …
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Export a MySQL Table to a CSV File Methods Overview

A comma-separated values (CSV) file is a simple file format that is widely supported, so it is often used to move tabular data between different computer programs that support the format. CSV file is a text format for a database table. Each record in the table is one line of the text file. Each field value of a record is separated from the next with a comma. For example, a CSV file might be used to transfer information from a database to a spreadsheet or another database. Of course, there are more advanced formats to store data, for example, XML, but CSV does have one advantage over XML. CSV has much lower overhead, thereby using much less bandwidth and storage than XML.

Now let’s analyse how one can save data from a MySQL table to a CSV file.


The first and very likely the easiest way is to change Storage Engine to CSV and save it to some archived file …

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Export a MySQL Table to a CSV File Methods Overview

In this article we describe benefits and shortcomings of different ways of exporting data from a MySQL table to the CSV format.

What is this MySQL file used for?

MySQL keeps many different files, some contain real data, some contain meta data. Witch ones are important? Witch can your throw away?

This is my attempt to create a quick reference of all the files used by MySQL, whats in them, what can you do if they are missing, what can you do with them.

When I was working for Dell doing Linux support my first words to a customer where “DO YOU HAVE COMPLETE AND VERIFIED BACKUP?” Make one now before you think about doing anything I suggest here.

You should always try to manage your data through a MySQL client.  If things have gone very bad this may not be possible. MySQL may not start. If your file system get corrupt you may have missing files. Sometimes people create other files in the MySQL directory (BAD).  This should help you understand what is safe to remove.

Before you try to work with one of these files make sure you have the file permissions set …

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Resolve many-to-many relations a bit different with MySQL

In database modeling, a m:n relationship is usually resolved by an additional table. But what if this relation is used only for archiving and the number of links in the resulting table is not too high? In that context, I got the idea to store all referring ID's as CSV string directly into a TEXT column of one of the referring tables. I came to this idea, because otherwise I would have to build complicated foreign keys and this way I also save one additional table. Certainly, this only makes sense if the data is not frequently accessed as foreign key. Nevertheless, I would like to tackle the problem, even if the implementation is very MySQL-oriented.

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MySQL Network Connections

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If your MySQL server has hundreds of clients (applications) and tens of thousands of queries per second,  MySQL default network settings may NOT be for you.  Network performance is not often a significant factor in the performance of MySQL.  That said, there are things to consider.

If you are building new applications make these changes now.  Developer expectations are hard to change.  My example below will break your application if  developers open a database connections and then spend ten minutes playing with their play doe before making a query.  If you have working applications …

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About CSV Tables

As most of MySQL users, I have often ignored what I'd like to call the minor storage engines. MYISAM, InnoDB and NDB (aka MySQL Cluster) are well covered in several articles; but what about engines like CSV or ARCHIVE? As part of some internal projects, we have been playing around with these 2 with some interesting results. On this article I'll concentrate on CSV.
ScenarioCurrently we have a few servers that are storing historical data that will eventually be migrated into Oracle. Two things need to happen until we can finally decommission them: 1) export the data to CSV so it can be imported in bulk into Oracle and 2) keep the data online so it can be queried as needed until the migration is finalized. I thought it would be interesting if we could solve both issues simultaneously and decided to try the CSV engine. Here's a description of the process.
Understanding CSV EngineThe CSV engine, as far as I can tell, was and example …

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MySQL 5.1 and InnoDB Hot Backup Gotcha

Recently while we were building a slave with a newer version of MySQL 5.1 from an InnoDB Hot backup, the following error occurred when we ran mysql_upgrade:

mysql.time_zone                                    OK
mysql.time_zone_leap_second                        OK
mysql.time_zone_name                               OK
mysql.time_zone_transition                         OK
mysql.time_zone_transition_type                    OK
mysql.user                                         OK
Running 'mysql_fix_privilege_tables'...
ERROR 13 (HY000) at line 311: Can't get stat of './mysql/general_log.CSV' (Errcode: 2)
ERROR 13 (HY000) at line 316: Can't get stat of './mysql/slow_log.CSV' (Errcode: 2)
FATAL ERROR: Upgrade failed

The problem is that in MySQL 5.1, it is possible to log the slow query log and general log to tables in the mysql schema (source: Selecting General Query and Slow Query Log Output Destinations). These tables are …

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