Mysql show processlist output explanation

Mysql show processlist output explanation 1. start mysql and enter show processlist. If you have the SUPER permission, you can view all the threads. Otherwise, you can only view the self-initiated threads (this refers, the current corresponding MySQL account running thread ). The data format is as follows (only three screenshots are taken): mysql> show processlist; + ----- + ------------- + ------------------ + ------- + --------- + ------- + hour + ---------- | Id | User | Host | db | Command | Time | State | Info + ----- + ------------- + -------------------- + ------- + --------- + ------- + -------------------------------- + ---------- | 207 | root | 192.168.0.20: 51718 | mytest | Sleep | 5 | NULL | 208 | root | 192. 168.0.20: 51719 | mytest | Sleep | 5 | NULL | 220 | root | 192.168.0.20: 51731 | mytest | Query | 84 | Locked | select bookname, culture, value, type from book where id = 001 first briefly describes the meaning and purpose of each column. The first column, id, needless to say, is an identifier. It is useful when you want to kill a statement. The user column displays the user before the ticket. If it is not the root user, this command only displays the SQL statements within your permission range. Host column, indicating the port from which the statement is sent. Well, it can be used to track users with problematic statements. Db column to display the database to which the process is currently connected. Command column, showing the commands executed by the current connection, which is generally sleep, query, and connect ). Time column, the duration of this state, in seconds. The state column displays the status of the SQL statement that uses the current connection. It is an important column and will be described in the future. Note that the state is only a certain state in the statement execution, for an SQL statement that has been queried as an example, it may need to pass through the copying to tmp table, Sorting result, Sending data and other statuses to complete the SQL statement. The info column displays this SQL statement because the length is limited, therefore, long SQL statements are not displayed completely, but an important basis for determining a problematic statement. The most important part of this command is the state column. mysql lists the following States: the Checking table is Checking the data table (this is automatic ). Closing tables is refreshing the modified data in the table to the disk and Closing the used table. This is a very fast operation. If not, check whether the disk space is full or the disk is under a heavy load. Connect Out replication the slave server is connecting to the master server. Copying to tmp table on disk because the temporary result set is larger than tmp_table_size, the temporary table is being converted from memory storage to disk storage to save memory. Creating tmp table is Creating a temporary table to store some query results. The deleting from main table server is executing the first part of multi-table deletion. The first table has just been deleted. The deleting from reference tables server is executing the second part of multi-Table deletion and deleting records of other tables. Flushing tables is executing flush tables, waiting for other threads to close the data table. Killed sends a kill request to a thread, which will check the kill flag and discard the next kill request. MySQL checks the kill flag in each primary loop. However, in some cases, the thread may die after a short period of time. If the thread is locked by other threads, the kill request will take effect immediately when the lock is released. Locked is Locked by other queries. Sending data is processing the SELECT query record and Sending the result to the client. Sorting for group is Sorting group. Sorting for order is Sorting order. The Opening tables process should be fast unless it is disturbed by other factors. For example, a data TABLE cannot be opened by another thread before the alter table or lock table statement is executed. Opening a table. Removing duplicates is executing a select distinct query, but MySQL cannot optimize those duplicate records in the previous stage. Therefore, MySQL needs to remove duplicate records and then send the results to the client. The Reopen table obtains the lock for a table, but the lock can be obtained only after the table structure is modified. The lock has been released, the data table is closed, and the data table is being re-opened. The Repair by sorting Repair command is being sorted to create an index. The Repair with keycache Repair command is using the index cache to create a new index one by one. It is slower than Repair by sorting. Searching rows for update: the matching records are found for update. It must be completed before the related record is updated. Sleeping is waiting for the client to send a new request. System lock is waiting for an external System lock to be obtained. If multiple mysqld servers are not running to request the same table at the same time, you can add the -- skip-external-locking parameter to disable external system locks. Upgrading lock insert delayed is trying to get a lock table to INSERT a new record. Updating is searching for matched records and modifying them. User Lock is waiting for GET_LOCK (). Waiting for tables this thread is notified that the data table structure has been modified. You need to re-open the data table to obtain the new structure. Then, in order to re-open the data table, you must wait until all other threads close the table. This notification is generated in the following situations: flush tables tbl_name, alter table, rename table, repair table, analyze table, or optimize table. Waiting for handler insert insert delayed has completed all the insert operations to be processed and is waiting for new requests. Most States correspond to fast operations. As long as one thread remains in the same state for several seconds, a problem may occur and you need to check it. Other statuses are not listed above, but most of them are only needed to check whether there are errors on the server.