Enfants has lines and FichiersEnfants has lines. Any suggestions? The difference in performance is possibly due to e. Without a full definition of both tables, and all of their indexes, it's not possible to tell for certain. In the case of your query, I don't think you need to change the code at all. But you may benefit from changing the indexes. You mention that you want to access many fields.
Putting all those fields in a composite index is porbably not the best solution. Every InnoDB table has a special index called the clustered index where the data for the rows is stored:. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
Collectives on Stack Overflow. Learn more. MySql Query very slow Ask Question. The value can be specified to a resolution of microseconds.
By default, administrative statements are not logged, nor are queries that do not use indexes for lookups. By default, the slow query log is disabled.
With an argument of 0, this option disables the log. The server creates the file in the data directory unless an absolute path name is given to specify a different directory. If a log file already is open, it is closed and the new file is opened. The server writes less information to the slow query log if you use the --log-short-format option. Even with that variable enabled, the server does not log queries that would not benefit from the presence of an index due to the table having fewer than two rows.
When queries that do not use an index are logged, the slow query log may grow quickly. By default, this variable is 0, which means there is no limit. Positive values impose a per-minute limit on logging of queries that do not use indexes. The first such query opens a second window within which the server logs queries up to the given limit, then suppresses additional queries. If there are suppressed queries when the window ends, the server logs a summary that indicates how many there were and the aggregate time spent in them.
The next second window begins when the server logs the next query that does not use indexes. The server uses the controlling parameters in the following order to determine whether to write a query to the slow query log:. By default, a replica does not write replicated queries to the slow query log. We use cookies to improve your experience with our site. By continuing to use this site, you consent to our use of cookies. Learn more. Downloads Products Blog Forums.
Toad World Blog. Need help managing data? Try Toad for free! Popular Posts. Recent Posts. You can either flip through all the pages, or you can pull on the right letter tab to quickly locate the name you need. Use indexes to avoid unnecessary passes through tables.
For example, you can add an index on picture. Now if you run the query, the process no longer involves scanning the entire list of pictures. First, all the albums are scanned to find the ones that belong to the user. This reduces the number of rows scanned to , The query is also about times faster than the original. Each table uses a key for an optimal performance, making the query times faster than the original.
This doesn't mean that you should add indexes everywhere because each index makes it longer to write to the database. You gain on read but lose on write. So only add indexes that actually increase read performance. If you're interested in attending the conference use this discount code when you register , for our readers: PCOS. Very good article! Perhaps you should mention the mysqldumpslow tool too. Surely the whole point of using a relational database is predicated upon normalisation.
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