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Search Results for: long run query

How to debug long-running transactions in MySQL

Among the many things that can cause a “server stall” is a long-running transaction. If a transaction remains open for a very long time without committing, and has modified data, then other transactions could block …

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Long Index Keys

In this post we’ll describe a query that accrued significant performance advantages from using a relatively long index key. (This posting is by Zardosht and Bradley.) We ran across this query recently when interacting with …

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MySQL random freezes could be the query cache

I feel like I’ve been seeing this a lot lately. occasionally, seemingly innocuous selects take unacceptably long. Or Over the past few weeks, we’ve been having bizarre outages during which everything seems to grind to …

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Poor man’s query logging

Occasionally there is a need to see what queries reach MySQL. The database provides several ways to share that information with you. One is called general log activated with

(or

in MySQL 5.1+) …

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Beware of running ANALYZE in Production

As you might know ANALYZE TABLE just quickly updates table statistics using index dives, unlike with MyISAM when it scans indexes holding table lock for long period of time. So ANALYZE TABLE should be very …

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Apache PHP MySQL and Runaway Scripts

Sometimes due to programming error or due to very complex query you can get your PHP script running too long, well after user stopped waiting for the page to render and went browsing other sites. …

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How to estimate query completion time in MySQL

Have you ever run a query in MySQL and wondered how long it’ll take to complete? Many people have had this experience. It’s not a big deal until the query has been running for an …

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TPC-H Run on MySQL 5.1 and 6.0

We were doing MySQL Performance evaluation on TPC-H queries for the client and they kindly allowed us to publish results which are very interesting. This is obviously not audited TPC-H run, and it can’t be …

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Enabling/Disabling query log without server restart in MySQL 5.0

General query logging can be very handy in MySQL on profuction server for various debugging needs. Unfortunately you can’t switch it on and off without restarting server until MySQL 5.0. What can you do in …

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Query Profiling with MySQL: Bypassing caches

Quite frequently I run into question like this “I’m using SQL_NO_CACHE but my query is still much faster second time I run it, why is that ? The answer to this question is simple – …

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