Search Results for: merge

The Optimization That (Often) Isn’t: Index Merge Intersection

Prior to version 5.0, MySQL could only use one index per table in a given query without any exceptions; folks that didn’t understand this limitation would often have tables with lots of single-column indexes on columns which commonly appeared in their WHERE clauses, and they’d wonder why the EXPLAIN plan for a given SELECT would […]

Preventing MySQL Emergencies Webinar

On the 25th of January at 10 am PST, I will present a webinar on preventing MySQL emergencies titled “Preventing Downtime in Production MySQL Servers”. The material I will present is based on in-depth research done by Percona across many production servers.  We analyzed more than 150 emergency cases and categorized our findings to help […]

White Paper: Preventing MySQL Emergencies

About a year ago, I started a study of emergency incidents that our customers filed with us. What I found was really surprising, and defied conventional wisdom. I learned a lot about preventing emergencies. I just published the outcome as a white paper, including checklists that you can use and modify for your own servers. […]

Multi Column indexes vs Index Merge

The mistake I commonly see among MySQL users is how indexes are created. Quite commonly people just index individual columns as they are referenced in where clause thinking this is the optimal indexing strategy. For example if I would have something like AGE=18 AND STATE=’CA’ they would create 2 separate indexes on AGE and STATE […]

AUTO_INCREMENT and MERGE TABLES

How would you expect AUTO_INCREMENT to work with MERGE tables ? Assuming INSERT_METHOD=LAST is used I would expect it to work same as in case insertion happens to the last table… which does not seems to be the case. Alternatively I would expect AUTO_INCREMENT to be based off the maximum value across all tables, respecting […]

Possible optimization for sort_merge and UNION ORDER BY LIMIT

Every so often you need to perform sort results retrieved from MySQL when your WHERE clause goes beyound col=const values which would allow MySQL to still use second portion of the index for the order by. Ranges as well as IN lists make this optimization impossible, not even speaking about index merge optimization. Lets look […]

Merge Tables Gotcha

I had the interesting customer case today which made me to do a bit research on the problem. You can create merge table over MyISAM tables which contain primary key and global uniqueness would not be enforced in this case, this is as far as most people will think about it. In fact however it […]

Percona now offering 24/7 support for MongoDB and TokuMX

Today Percona announced the immediate availability of 24/7, enterprise-class support for MongoDB and TokuMX. The new support service helps organizations achieve maximum application performance without database bloat. Customers have round-the-clock access (365 days a year) to the most trusted team of database experts in the open source community. The news means that Percona now offers […]

Fractal Tree library as a Key-Value store

As you may know, Tokutek is now part of Percona and I would like to explain some internals of TokuDB and TokuMX – what performance benefits they bring, along with further optimizations we are working on. However, before going into deep details, I feel it is needed to explain the fundamentals of Key-Value store, and […]

Bypassing SST in Percona XtraDB Cluster with incremental backups

Beware the SST In Percona XtraDB Cluster (PXC) I often run across users who are fearful of SSTs on their clusters. I’ve always maintained that if you can’t cope with a SST, PXC may not be right for you, but that doesn’t change the fact that SSTs with multiple Terabytes of data can be quite […]