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Search Results for: column

Hot Column Addition and Deletion Part II: How it works

Hot Column Addition and Deletion (HCAD) In the previous HCAD post, I described HCAD and showed that it can reduce the downtime of column addition (or deletion) from 18 hours to 3 seconds. In fact, …

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Hot Column Addition and Deletion Part I – Performance

From 18 hours to 3 seconds! Hot Column Addition and Deletion (HCAD) Overview TokuDB v5.0 introduces several features that are new to the MySQL world. In this series of posts, we’re going to present some …

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Testing MySQL column stores

Recently I had the opportunity to do some testing on a large data set against two MySQL column-store storage engines. I’d like to note that this effort was sponsored by Infobright, but this analysis reflects …

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How number of columns affects performance ?

It is pretty understood the tables which have long rows tend to be slower than tables with short rows. I was interested to check if the row length is the only thing what matters or …

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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 …

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A Second Rule of Thumb for Choosing Column Order in Indexes

A couple of weeks ago, Baron Schwartz wrote an interesting post describing a rule of thumb he sometimes uses to choose the order of columns in an index. In a nutshell, he recommends putting highly …

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A rule of thumb for choosing column order in indexes

I wanted to share a little rule of thumb I sometimes use to decide which columns should come first in an index. This is not specific to MySQL, it’s generally applicable to any database server …

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Multiple column index vs multiple indexes

(There is an updated version of the content in this post by Percona’s Stephane Combaudon available here.) After my previous post there were questions raised about Index Merge on Multiple Indexes vs Two Column Index …

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Multi-Column IN clause – Unexpected MySQL Issue

We have an application which stores massive amount of urls. To save on indexes instead of using URL we index CRC32 of the URL which allows to find matching urls quickly. There is a bit …

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Fixing column encoding mess in MySQL

Just had an interesting issue with an encoding mess on a column containing non-ASCII (Russian) text. The solution was not immediately obvious so I decided it’s worth sharing. The column (actually the whole table) was …

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