Emergency

Monthly Archives: August 2007

Site was down today, support and web hosting.

During last one and a half year we had pretty good track record with MySQL Performance Blog – there were times when site was slow (especially when backup was running) but I do not remember …

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Working on “High Performance MySQL, Second Edition”, how you can help?

As you may already have seen announcement by Baron we’re working on major rewrite of High Performance MySQL book – the most famous book about MySQL Performance on the market… which is getting old though. …

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Guess what?! Microsecond slow query timing finally available in MySQL!

Vadim asked me yesterday to update Microslow patch for 5.1.21, because the previous one I wrote for 5.1.20 failed to apply correctly on the new MySQL release. Imagine the expression on my face after I …

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To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?

When we optimize clients’ SQL queries I pretty often see a queries with SQL_CALC_FOUND_ROWS option used. Many people think, that it is faster to use this option than run two separate queries: one – to …

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Do you always need index on WHERE column ?

I believe we wrote about this before, but this topic popups again and again. Today I’ve read opinion that if we have clause WHERE has_something=1 we should have index on column has_something (the column has …

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Redundant index is not always bad

About year ago Peter wrote about redundant indexes and mentioned sometimes it is good to leave two indexes, even one is first part of another. I’m speaking about BTREE indexes, for example, KEY (A), and …

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Memory allocation in Stored Function

UPDATE : Post is not actual anymore Not so long time ago I had task to update string column in table with 10mil+ rows, and, as the manipulation was non-trivial, I decided this task is …

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How fast can you sort data with MySQL ?

I took the same table as I used for MySQL Group by Performance Tests to see how much MySQL can sort 1.000.000 rows, or rather return top 10 rows from sorted result set which is …

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Should MySQL Extend GROUP BY Syntax ?

Jan has a good article about finding the row matching some value in the group: This is one illustration of group by limitations in SQL language which is not offset by any MySQL specific extensions,yet …

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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 …

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