This Log Buffer Edition covers various valuable blog posts from the fields of Oracle, SQL Server and MySQL.
Oracle:
What is Optimizer Trace? After reading topic about Optimizer Tracer by [Morgan Tocker][1] decided to test it. From [Optimizer Trace and EXPLAIN FORMAT=JSON in 5.7][2]: Optimizer trace is a new diagnostic tool introduced in MySQL 5.6 to show how the optimizer is working internally. It is similar to EXPLAIN, with a few notable differences: It doesn’t just show the intended execution plan, it shows the alternative choices. You enable the optimizer trace, then you run the actual query. It is far more verbose in its output. For understanding goal of article please read previous one about related verified optimizer BUG: [Playing with count() optimizer work][3] ** We have 2 queries: **select count() from sales; select count(*) from sales where sales_id > 0; Firstly let’s get explain plan for query with JSON format and as regular:
-- JSON
mysql> explain format=json select …The Big Data explosion in recent years has created a vast number of new technologies in the area of data processing, storage, and management. One of the biggest names to appear on the scene is Hadoop. In case you need a quick review, Hadoop is a Big Data storage system that takes in large amounts of data from servers and breaks it into smaller, manageable chunks. The technology is complex but at a high level the Hadoop ecosystem essentially takes a “divide and conquer” approach to processing Big Data instead of processing data in tables, as in a relational database like Oracle or MySQL.
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We previously covered basic tuning and configuration best practices for MyQL Galera Cluster on AWS. In this blog post, we’ll go over some AWS features/tools that you may find useful when managing Galera on Amazon Cloud. This won’t be a detailed how-to guide as each tool described below would warrant its own blog post. But this should be a good overview of how you can use the AWS tools at your disposal.
EBS backups
If you have chosen EBS volumes as storage for your database (you could have chosen ephemeral volumes too), you can benefit greatly from their ability of taking snapshots of the data.
In general, there are two ways of running backups:
Adrian Cockcroft really nailed it when he said that a monitoring system has to be more reliable than what it’s monitoring. I don’t mind admitting that in our first year or so, we had some troubles with losing telemetry data. Customers were never sure whether their systems were offline, the agents were down, or we were not collecting the data. Even a few seconds of missing data is glaringly obvious when you have 1-second resolution data. There’s nowhere to hide.
It was embarrassing and we made it a top priority to fix. And fix it we did. This isn’t news, but we never wrote about it, so it’s time. Hopefully this is helpful to someone else building systems like ours, where the workload is hard in unusual ways, …
[Read more]#DBHangOps 05/28/15 -- Deep Engine and more!
Hello everybody!
Join in #DBHangOps this Thursday, May, 28, 2015 at 11:00am pacific (19:00 GMT), to participate in the discussion about:
What does being a DBA mean to you?
You can check out the event page at https://plus.google.com/events/cgomeasl8m4fr47tl25e74rvh9g on Thursday to participate.
As always, you can still watch the #DBHangOps twitter search, the @DBHangOps …
[Read more]Many database vendors would like me to take a look at their products and consider adopting them for all sorts of purposes. Often they’re pitching something quite new and unproven as a replacement for mature, boring technology I’m using happily.
I would consider a new and unproven technology, and I often have. As I’ve written previously, though, a real evaluation takes a lot of effort, and that makes most evaluations non-starters.
Perhaps the most important thing I’m considering is whether the product is mature. There are different levels of maturity, naturally, but I want to understand whether it’s mature enough for me to take a look at it. And in that spirit, it’s worth understanding what makes a database mature.
For my purposes, maturity really means demonstrated capability and quality with a lot of …
[Read more]I accidentally stumbled upon this Stack Overflow question this morning:
I am wondering if there is any difference in regards to performance between the following:
SELECT ... FROM ... WHERE someFIELD IN(1,2,3,4); SELECT ... FROM ... WHERE someFIELD between 0 AND 5; SELECT ... FROM ... WHERE someFIELD = 1 OR someFIELD = 2 OR someFIELD = 3 ...;
It is an interesting question because there was no good way to answer it when it was asked in 2009. All of the queries resolve to the same output in EXPLAIN. Here is an example using the sakila schema:
mysql> EXPLAIN SELECT * FROM film WHERE film_id BETWEEN 1 AND 5\G
mysql> EXPLAIN SELECT * FROM film WHERE film_id IN (1,2,3,4,5)\G
mysql> EXPLAIN SELECT * FROM film WHERE film_id =1 or film_id=2 or film_id=3 or film_id=4 or film_id=5\G
********* 1. row *********
id: 1 …[Read more]
History is repeating again. MongoDB is breaking out of the niche into the mainstream, performance and instrumentation are terrible in specific cases, MongoDB isn’t able to fix all the problems alone, and an ecosystem is growing.
This should really be a series of blog posts, because there’s a book’s worth of things happening, but I’ll summarize instead. Randomly ordered:
Fri, 2015-05-22 07:19geoff_montee_g
Out-of-order parallel replication is a great
feature in MariaDB 10.0 that improves replication performance by
committing independent transactions in parallel on a slave. If
slave_parallel_threads is greater
than 0, then the SQL thread will instruct multiple worker threads
to concurrently apply transactions with different domain IDs.
If an application is setting the domain ID, and if parallel replication is enabled in MariaDB, then out-of-order parallel replication should mostly work automatically. However, depending on an …
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