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Displaying posts with tag: MySQL 8 (reset)
Error Logging in MySQL 8

Although only available as a Release Candidate, MySQL 8 is already proving itself to be a huge leap forward in many regards. Error logging is no exception. The MySQL development team just announced that they have redesigned the error logging subsystem to use a new component architecture.

The redesign will allow the filtering of log events, as well as the routing of error log output to multiple destinations, via the enabling of multiple sink components.  This will make it possible to send error log events to third-party systems for additional formatting and analysis.

In today’s blog, we’ll explore how to employ MySQL 8’s component-based error logging to achieve a variety of logging configurations. Note that all this is specific for MySQL 8 and is not available in earlier versions and also not in MariaDB. However, MariaDB has an option to write the error log to the system “syslog” on systemd-based Linux variants – …

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Array Ranges in MySQL JSON

Pretend you have a JSON array of data that looks roughly like the following.

mysql> insert into x(y) values('["a","b","c","d"]');
Query OK, 1 row affected (0.10 sec)


You could get all the values from that array using $[*]


mysql> select y->"$[*]" from x;
+----------------------+
| y->"$[*]" |
+----------------------+
| ["a", "b", "c", "d"] |
+----------------------+
1 row in set (0.00 sec)

Or the individual members of the array with an index that starts with zero.


mysql> select y->"$[0]" from x;
+-----------+
| y->"$[0]" |
+-----------+
| "a" |
+-----------+
1 row in set (0.00 sec)


But what about the times you want the last item in the array and really do not want to loop through all the items? How about using …

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How to use MySQL 8.0.4 with a GUI

If you want to have a look on what is about to come in the new version of the popular database and is used to Syntax Highlighting you don’t need to be chained to the Terminal.

Some of you may use tools like MySQL Workbench or Sequel Pro (as of the release of this post both tools had the following error occurring), and even if you are using the Terminal (if you are using an old version of mysql​, like 5.7) you may encounter this error:

Unable to connect to host 127.0.0.1, or the request timed out.

Be sure that the address is correct and that you have the necessary privileges, or try increasing the connection timeout (currently 10 seconds).

MySQL said: Authentication plugin ‘caching_sha2_password’ cannot be loaded: …

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Common Table Expressions (CTEs) Part 1

Occasionally at conference or a Meetup, someone will approach me and ask me for help with a MySQL problem.  Eight out of ten times their difficulty includes a sub query. "I get an error message about a corrugated or conflabugated sub query or some such,"  they say, desperate for help.  Usually with a bit of fumbling we can get their problem solved.  The problem is not a lack of knowledge for either of us but that sub queries are often hard to write. 

MySQL 8 will be the first version of the most popular database on the web with Common Table Expressions or CTEs.  CTEs are a way to create temporary tables and then use that temporary table for queries. Think of them as easy to write sub queries!

WITH is The Magic WordThe new CTE magic is indicated with the WITH clause.

mysql> WITH myfirstCTE 
AS (SELECT * FROM world.city WHERE …
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MySQL Queries No Waiting

Last time we looked at SKIP LOCKED where rows locked by another process were skipped. NOWAIT informs the server to return immediately IF the desired rows can not be locked.

How To Use NOWAIT Start a connection to your MySQL 8 server, start a transaction, and make a query to lock up part of the data. mysql>START TRANSACTION; mysql>SELECT * FROM city WHERE countryCode = 'USA' FOR UPDATE;
On a second connection, start a transaction and issue a SELECT query with NOWAIT. mysql>START TRANSACTION; mysql>SELECT * FROM city WHERE countryCode = 'USA' FOR UPDATE NOWAIT;
The second connection will get a message saying 'statement aborted because lock(s) could not be acquired immediately and NOWAIT is SET
So if you can come back later to lock the records or just can not …

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SKIP LOCKED

SKIP LOCKED is a new feature in MySQL 8 that many will find valuable.  If allows you to not wait about for locked records and work on what is available -- the unlocked records.
How To Use SKIP LOCKED The MySQL world database has 274 records in the city table where the countryCode field equals 'USA' there are 274 records. From past interactions, we somehow know there are some records with the ID field greater than 4000.
On MySQL shell number 1, start a transaction and lock some records mysql>START TRANSACTION; mysql>SELECT * FROM city WHERE ID > 4000 and countryCode = 'USA'; There will be 66 records.
On MySQL shell number number 2, start a transaction and lets try to lock the records starting at IS 3990 and up. mysql>START TRANSACTION; mysql>SELECT FROM city WHERE id > 3990 and countryCode='USA'
FOR UPDATE SKIPPED LOCKED;
There will be 10 records.  The records …

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MySQL Shell with Command Completion

MySQL ShellCLI Interfaces are usually boring, ASCII-ish functional interfaces that are as about as exciting as paint drying or end user license agreements for your rice steamer. They get the job done but no excitement. The new MySQL Shell (mysqlsh instead of mysql at the command line is a great new tool but like its predecessor it is not exactly visually dynamic.

Until Now.

At labs.mysql.com there is a new version of the MySQL Shell that adds some new functionality and some visual enticements. I was in a session at Oracle OpenWorld and was impressed by not only the visually stunning upgrade but by the fact that we now get command auto-completion!

You can login as you did with the old shell but then you see that little bit …

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MySQL 8's Windowing Function Part 1

MySQL will have Windowing functions and CTEs which will mean it will be easier to do data analysis with MySQL. You can now make calculations on data from each row in a query plus rows related to that row. Windows will make it easier to group items when GROUP BY does not meet needs. This is a great breakthrough but the new documentation has a steep learning curve if you are starting from zero. Hopefully this and following blogs will make it easier to get started with Windowing Functions. OVER & WINDOW as a keywords Let's start with the world_x sample database. The sample below orders the city table by the CountryCode but notice the window w as (order by CountryCode) phrase. This sets up a group for analysis, or a window on the data. For this example we will get the row number, rank, and dense rank of the data in that group. So for CountryCode of ABW we get a row number of 1, rank of 1, …

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From MySQL 8.0.0 to MySQL 8.0.1 – or any other dev milestone

Disclaimer: This post is aimed to you, the curious developer, sys-admin, technologist, whatever-title-you-use. DO NOT run the following lines on production. Not even in a stable environment, do this if you don’t care about the outcome of the current data.

If you want to keep up with the newest MySQL developer milestones I have news for you: there is no upgrade available for milestone versions. The way to go is to remove old version and install new one, according to their website:

Upgrades between milestone releases (or from a milestone release to a GA release) are not supported. For example, upgrading from 8.0.0 to 8.0.1 is not supported, as neither are GA status releases.

So if you, like me, had the 8.0.0 version and want to test the 8.0.1 (alhtough 8.0.3 milestone is already in development) …

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Testing MySQL 8.0 – let me create a ton of undo files

This is the late blog post about 2 recent bug reports
#85969
#85971

The basic idea came after reading -> http://mysqlserverteam.com/the-mysql-8-0-1-milestone-release-is-available/

So the result of test ->
After each restart of MySQL the new undo log files are going to be created + keeping old files.

shahriyar.rzaev@qaserver-06:~/sandboxes/msb_8_0_1/data$ du -hs
6.4G    
# The count of undo files
shahriyar.rzaev@qaserver-06:~/sandboxes/msb_8_0_1/data$ ls | grep undo | wc -l
539

After new restart:

# New count
shahriyar.rzaev@qaserver-06:~/sandboxes/msb_8_0_1/data$ ls | grep undo | wc -l
616

So how to …

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