mysql temp table performance

When the data volume is very large (the table capacity reaches GB or TB), if you still use the index method to optimize the query, due to the consumption of the index and the generation of a large number of index fragments, the query process will lead to a large number of random I/O generation. In this scenario, unless the index can be well overwritten, the data table must be queried Based on the index, the

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large, the my.cnf key_buffer_size should be larger. Can calculate the cache failure rate with key_reads/key_read_requests 3. If the handler_read_rnd is too large, then many of the queries in the SQL statement you write are to scan the entire table without playing the role of the index key 4. If the threads_created is too large, it is necessary to increase the value of thread_cache_size in MY.CNF. You can use Threads_created/connections to calculate

MySQL Query performance optimizationThe optimization of MySQL query performance involves many aspects, including library table structure, establishing reasonable index and reasonable query. The library table structure includes how

Tags: scenario date Another content like common is the CTO solvesA Meaning of with ASThe with as phrase, also called the subquery section (subquery factoring), allows you to do many things, defining a SQL fragment that will be used by the entire SQL statement. Sometimes it is to make the SQL statement more readable, or it may be in different parts of union all as part of providing data.Especially useful for union all. Because each part of union all may be the same, but if each part goes through

Tags: style blog http io color ar using for SPExt.: http://wudataoge.blog.163.com/blog/static/80073886200961652022389/A Meaning of with ASThe with as phrase, also called the subquery section (subquery factoring), allows you to do many things, defining a SQL fragment that will be used by the entire SQL statement. Sometimes it is to make the SQL statement more readable, or it may be in different parts of union all as part of providing data.Especially useful for union all. Because each part of unio

of each month. When it is necessary to generate a report based on data from all 12 log tables, this means that multiple table queries need to be written and updated to reflect the information in those tables. Instead of writing these queries that may have errors, instead of merging the tables with a single query and then deleting the Mer GE table without affecting the original data, deleting the merge

Label:Today, database operations are increasingly becoming a performance bottleneck for the entire application, which is especially noticeable for web applications. It's not just about the performance of the database that DBAs need to worry about, it's something that our programmers need to focus on. When we design the database table structure, we need to pay att

table, if the increase can also be separate head portrait for a separate table (such as Baidu separate picture server) Read and write separation: The Web program is slow, the first test object is the database, wrote a few years of program are aware. Now you want to track down the SQL statements in MySQL that drag server

; temporary_tables) | Write_create_table_bin_log () Case sqlcom_drop_table: | If (! Lex-> drop_temporary) | Determine whether temporarytable is explicitly written in the statement | Mysql_rm_table () | Mysql_rm_table_part2 () | For (Table-> next_local) | Drop_temporary_table () // find and delete from Thr-> temporarylist | Delete an object table In summary, we can know that the temporary

[Switch] MySql modifies the table type and mysql modifies the table Recently, I encountered a problem about modifying the mysql table type. Previously, when phpmyadmin managed the mysql

received select statement in string mode based on the preset hash algorithm, then, go to the Query Cache to check whether the data has been cached. That is to say, if the select request is already in the cache, the data will be directly returned, thus omitting all subsequent steps (such as SQL statement parsing, optimizer optimization and Data Request to the storage engine), greatly improving performance. Of course, Query Cache also has a fatal defec

and the version with the Google patch installed, this option can be set in microseconds. this is a great feature, because once you have eliminated all queries whose query time exceeds 1 second, the adjustment is very successful, which helps you eliminate the problem SQL before the problem increases. 3. log_queries_not_using_indexes Enabling this option is a good idea. it actually records the query that returns all rows. Summary We have introduced five categories of

Today, database operations are increasingly becoming a performance bottleneck for the entire application, especially for Web applications. As for the performance of the database, this is not just something that DBAs need to worry about, and that's what we programmers need to focus on. When we design the database table structure, we need to pay attention to the

wait for the lock ). For example: thread 1 does 1000 insertsthread 2, 3, and 4 does 1 insertthread 5 does 1000 inserts If you do not use the lock, 2, 3, and 4 will be completed before 1 and 5. If you use locking, 2, 3, and 4 may not be completed before 1 or 5, but the overall time should be about 40% faster. Because INSERT, UPDATE, and DELETE operations are fast in MySQL, you will get better overall performance