Explain analyze mysql

It will plan the query, instrument it and execute it while counting rows and measuring time spent at various points in the execution plan. Explain Analyze which runs the query and measures execution time by using the new iterator executor for each step. When EXPLAIN is used with an explainable statement, MySQL displays information from the optimizer about the statement execution plan.

That is, MySQL explains how it would process the statement, including information about how tables are joined and in which order. EXPLAIN Output Format page of the MySQL Reference Manual open because I kept forgetting what all of the values for the columns meant. I was always looking at the explain table and thinking, “what is this telling me? The EXPLAIN output shows that it has to go through 14048rows, which is about all the rows in the table.

The Extra column indicates that MySQL tries to reduce the amount of rows it inspects using the WHERE clause, but it estimates to reduce those to , which is still ba as = million rows. ALTER TABLE Statement”, and Section 22. Maintenance of Partitions”.

During the analysis , the table is locked with a read lock for InnoDB and MyISAM. How to optimize the MySQL Query? MySQL Query Analyzer lets you accurately pinpoint SQL code that is the root cause of a slow down. What is query optimization? I think I’m going to add a “share” feature so that you can get a permalink with all of the values saved.

EXPLAIN ANALYZE is a profiling tool for your queries that will show you where MySQL spends time on your query and why. Using the analyzer is very simple. The EXPLAIN keyword is used throughout various SQL databases and provides information about how your SQL database executes a query.

If you just want to measure the execution time but the function runs too fast to meaningfully measure then you can use the BENCHMARK() function to repeatedly call the function. EXPLAIN is one of the most powerful tools at your disposal for understanding and optimizing troublesome MySQL queries, but it’s a sad fact that many developers rarely make use of it. Visualize query activity to gain further insight into performance beyond query statistics. Filter for specific query problems like full table scans and bad indexes.

EXPLAIN EXTENDED provides additional information and estimates the number of table rows. Let’s start with the tools you can use to predict a query’s future. The venerable EXPLAIN command has been with us a long time as a built-in MySQL utility statement. In the beginning, there was EXPLAIN. Its purpose is to explain that what the optimizer predicts is the best “plan” and describe that to us.

Content reproduced on this site is the property of the respective copyright holders. For users of HeidiSQL this is now even easier. As discussed in their news post you can now send a query to the EXPLAIN analyzer with a single click. Once you append the query before an SQL statement, MySQL displays information from the optimizer about the intended execution plan. ANALYZE statement runs a statement and returns information about its execution plan.

EXTENDED keyword which provides you with some helpful additional information on query optimization. It should be used together with SHOW WARNINGS to get information about how query looks after transformation as well as what other notes the optimizer may wish to tell us. The first one is always not slower than the secon and in some cases it is faster. The key column indicates the key (index) that MySQL actually decided to use. If MySQL decides to use one of the possible_keys indexes to look up rows, that index is listed as the key value.

It is possible that key will name an index that is not present in the possible_keys value. When you precede a SELECT statement with the keyword EXPLAIN , MySQL displays information from the optimizer about the statement execution plan. Depends on your version of MySQL and storage engine but in general: OPTIMIZE TABLE Analyzes table, stores the key distribution for a table, reclaims the unused space and defragments the data file.

ANALYZE TABLE Only analyzes table and stores the key distribution.