Why is this mysql query so slow?

Why is this mysql query so slow?

Why is this mySQL query extremely slow? Given is a mySQL table named “orders_products” with the following relevant fields: Both fields are indexed. This query takes extremely long, around 20 seconds. The database is not very busy otherwise, and performs well on other queries. I am wondering, what causes the query to be so slow?

How long does it take for MySQL Query to finish?

This query will finish in ~100ms normally. However, after 2~3 days of uptime, the query time will suddenly increase to about 200 seconds. This will usually last 4~6 hours before it gets back to its normal state (~100ms). If I restart MySQL in the period, there is a chance (about 50%) to solve the slowdown (temporary).

Can a slow resolver cause a slow connection?

However, a slow resolver can definitely have an effect when connecting to the server – if users get access based on the hostname they connect from. MySQL also have an option for logging the hostname of connections. The mysql-report doesn’t say much about indexes.

Why are there so many long running queries in MySQL?

Long running queries/statements/transactions are sometimes inevitable in a MySQL environment. In some occasions, a long running query could be a catalyst to a disastrous event. If you care about your database, optimizing query performance and detecting long running queries must be performed regularly.

What happens when a long running query is executed?

In some worse-case scenario, a long running query could cause a total service disruption like server down, server crash and connections maxing out. If you see a query takes longer than usual to execute, do investigate it.

Why does MySQL connection take so long to open?

Slow connections could be caused by the amount of memory consumed by each DB Connection being allocated. Back on April 24, 2012, I answered the post How costly is opening and closing of a DB connection?.

How to use indexes to improve mysql query performance?

Database indexes in MySQL enable you to accelerate the performance of SELECT query statements. For small tables, an index does not help much. However, if you have tables with a large amount of data, indexes can dramatically improve performance. The following behaviors are all indications that tables may benefit from adding indexes:

Are there any performance issues with MySQL database?

Performance issues are common problems when administering MySQL databases. Sometimes these problems are, in fact, due to slow queries. In this blog, we’ll deal with slow queries and how to identify these. MySQL has the capability to filter and log slow queries.

How to identify performance issues with slow queries?

Performance issues are common problems when administering MySQL databases. Sometimes these problems are, in fact, due to slow queries. In this blog, we’ll deal with slow queries and how to identify these.

How to determine which tables may benefit from using indexes?

To determine which tables may benefit from using indexes, you must analyze your database queries. The EXPLAIN SELECT statement helps you do this. To analyze database queries, follow these steps: Log in to your account using SSH. At the Enter Password prompt, type your password. The mysql> prompt appears.

How can I check mysql query optimizer output?

If you are using a third-party application, such as WordPress or PrestaShop, you may need to examine the source code or database logs to determine the exact SELECT statements that are used to retrieve data. Output from the EXPLAIN SELECT statement shows how the MySQL query optimizer will execute the query.