Emergency

Search Results for: difference between random storage and sequential storage

Full table scan vs full index scan performance

Earlier this week, Cédric blogged about how easy we can get confused between a covering index and a full index scan in the EXPLAIN output. While a covering index (seen with EXPLAIN as Extra: Using …


Three Ways that Fractal Tree Indexes Improve SSD for MySQL

Since Fractal Tree indexes turn random writes into sequential writes, it’s easy to see why they offer a big advantage for maintaining indexes on rotating disks. It turns out that that Fractal Tree indexing also …


Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5

This is the second blog post in the series of blog posts leading up to the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. This blog post is aimed at the optimizer …


Write Optimization: Myths, Comparison, Clarifications

Some indexing structures are write optimized in that they are better than B-trees at ingesting data. Other indexing structures are read optimized in that they are better than B-trees at query time. Even within B-trees, …


TokuDB FAQ

Links to the FAQ Sections can be found here: General Information Open Source Technical Details Best Practices and Tools General Information ANY CHARACTER HERE 1.    What is TokuDB? TokuDB is an ACID compliant storage engine for …


The MySQL optimizer, the OS cache, and sequential versus random I/O

In my post on estimating query completion time, I wrote about how I measured the performance on a join between a few tables in a typical star schema data warehousing scenario. In short, a query …


Hacking for Faster Insertions: Is this really how you want to spend your time?

Recall that I’ve claimed that it takes 28 years to fill a disk with random insertions, given a set of reasonable assumptions. Recall what they are: We are focusing on the storage engine (a la …


How much overhead is caused by on disk temporary tables

As you might know while running GROUP BY and some other kinds of queries MySQL needs to create temporary tables, which can be created in memory, using MEMORY storage engine or can be created on …


Why MySQL could be slow with large tables ?

If you’ve been reading enough database related forums, mailing lists or blogs you probably heard complains about MySQL being unable to handle more than 1.000.000 (or select any other number) rows by some of the …