mysql "show processlist"命令

        mysql中的 show processlist 命令是MySQL数据库中运用最多的命令，通过该命理可以查看到mysql所的进程状态，所以对show processlist 的状态进行理解和确认，也就显得非常必要了。

        

        MySQL官方文档中，对于show processlist的说明如下：

http://dev.mysql.com/doc/refman/5.5/en/show-processlist.html

SHOW PROCESSLIST Syntax

SHOW [FULL] PROCESSLIST

SHOW PROCESSLIST shows you which threads are running. You can also get this information from theINFORMATION_SCHEMA PROCESSLIST table or the mysqladmin processlist command. If you have the PROCESSprivilege, you can see all threads. Otherwise, you can see only your own threads (that is, threads associated with the MySQL account that you are using). If you do not use the FULL keyword, only the first 100 characters of each statement are shown in the Info field.

This statement is very useful if you get the “too many connections” error message and want to find out what is going on. MySQL reserves one extra connection to be used by accounts that have the SUPER privilege, to ensure that administrators should always be able to connect and check the system (assuming that you are not giving this privilege to all your users).

Threads can be killed with the KILL statement. See Section 13.7.6.4, “KILL Syntax”.

Here is an example of SHOW PROCESSLIST output:

mysql> SHOW FULL PROCESSLIST\G
*************************** 1. row ***************************
Id: 1
User: system user
Host:
db: NULL
Command: Connect
Time: 1030455
State: Waiting for master to send event
Info: NULL
*************************** 2. row ***************************
Id: 2
User: system user
Host:
db: NULL
Command: Connect
Time: 1004
State: Has read all relay log; waiting for the slave
       I/O thread to update it
Info: NULL
*************************** 3. row ***************************
Id: 3112
User: replikator
Host: artemis:2204
db: NULL
Command: Binlog Dump
Time: 2144
State: Has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
*************************** 4. row ***************************
Id: 3113
User: replikator
Host: iconnect2:45781
db: NULL
Command: Binlog Dump
Time: 2086
State: Has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
*************************** 5. row ***************************
Id: 3123
User: stefan
Host: localhost
db: apollon
Command: Query
Time: 0
State: NULL
Info: SHOW FULL PROCESSLIST
5 rows in set (0.00 sec)

The columns produced by SHOW PROCESSLIST have the following meanings:

•  Id

  The connection identifier. This is the same type of value displayed in the ID column of theINFORMATION_SCHEMA.PROCESSLIST table, the PROCESSLIST_ID column of the Performance Schema threadstable, and returned by the CONNECTION_ID() function.

•  User

  The MySQL user who issued the statement. If this is system user, it refers to a nonclient thread spawned by the server to handle tasks internally. This could be the I/O or SQL thread used on replication slaves or a delayed-row handler. unauthenticated user refers to a thread that has become associated with a client connection but for which authentication of the client user has not yet been done. event_scheduler refers to the thread that monitors scheduled events. For system user, there is no host specified in the Host column.

•  Host

  The host name of the client issuing the statement (except for system user where there is no host). SHOW PROCESSLIST reports the host name for TCP/IP connections in host_name:client_port format to make it easier to determine which client is doing what.

•  db

  The default database, if one is selected, otherwise NULL.

•  Command

  The type of command the thread is executing. For descriptions for thread commands, see Section 8.12.5, “Examining Thread Information”. The value of this column corresponds to the COM_xxx commands of the client/server protocol and Com_xxx status variables. See Section 5.1.6, “Server Status Variables”

•  Time

  The time in seconds that the thread has been in its current state. For a slave SQL thread, the value is the number of seconds between the timestamp of the last replicated event and the real time of the slave machine. SeeSection 17.2.1, “Replication Implementation Details”.

•  State

  An action, event, or state that indicates what the thread is doing. Descriptions for State values can be found atSection 8.12.5, “Examining Thread Information”.

  Most states correspond to very quick operations. If a thread stays in a given state for many seconds, there might be a problem that needs to be investigated.

  For the SHOW PROCESSLIST statement, the value of State is NULL.

•  Info

  The statement the thread is executing, or NULL if it is not executing any statement. The statement might be the one sent to the server, or an innermost statement if the statement executes other statements. For example, if aCALL statement executes a stored procedure that is executing a SELECT statement, the Info value shows theSELECT statement.

对于其中 state 的状态值，有下面的范围：

http://dev.mysql.com/doc/refman/5.5/en/general-thread-states.html

 General Thread States

The following list describes thread State values that are associated with general query processing and not more specialized activities such as replication. Many of these are useful only for finding bugs in the server.

•  After create

  This occurs when the thread creates a table (including internal temporary tables), at the end of the function that creates the table. This state is used even if the table could not be created due to some error.

•  Analyzing

  The thread is calculating a MyISAM table key distributions (for example, for ANALYZE TABLE).

•  checking permissions

  The thread is checking whether the server has the required privileges to execute the statement.

•  Checking table

  The thread is performing a table check operation.

•  cleaning up

  The thread has processed one command and is preparing to free memory and reset certain state variables.

•  closing tables

  The thread is flushing the changed table data to disk and closing the used tables. This should be a fast operation. If not, verify that you do not have a full disk and that the disk is not in very heavy use.

•  converting HEAP to MyISAM

  The thread is converting an internal temporary table from a MEMORY table to an on-disk MyISAM table.

•  copy to tmp table

  The thread is processing an ALTER TABLE statement. This state occurs after the table with the new structure has been created but before rows are copied into it.

•  Copying to group table

  If a statement has different ORDER BY and GROUP BY criteria, the rows are sorted by group and copied to a temporary table.

•  Copying to tmp table

  The server is copying to a temporary table in memory.

•  Copying to tmp table on disk

  The server is copying to a temporary table on disk. The temporary result set has become too large (seeSection 8.4.4, “How MySQL Uses Internal Temporary Tables”). Consequently, the thread is changing the temporary table from in-memory to disk-based format to save memory.

•  Creating index

  The thread is processing ALTER TABLE ... ENABLE KEYS for a MyISAM table.

•  Creating sort index

  The thread is processing a SELECT that is resolved using an internal temporary table.

•  creating table

  The thread is creating a table. This includes creation of temporary tables.

•  Creating tmp table

  The thread is creating a temporary table in memory or on disk. If the table is created in memory but later is converted to an on-disk table, the state during that operation will be Copying to tmp table on disk.

•  deleting from main table

  The server is executing the first part of a multiple-table delete. It is deleting only from the first table, and saving columns and offsets to be used for deleting from the other (reference) tables.

•  deleting from reference tables

  The server is executing the second part of a multiple-table delete and deleting the matched rows from the other tables.

•  discard_or_import_tablespace

  The thread is processing an ALTER TABLE ... DISCARD TABLESPACE or ALTER TABLE ... IMPORT TABLESPACE statement.

•  end

  This occurs at the end but before the cleanup of ALTER TABLE, CREATE VIEW, DELETE, INSERT, SELECT, orUPDATE statements.

•  executing

  The thread has begun executing a statement.

•  Execution of init_command

  The thread is executing statements in the value of the init_command system variable.

•  freeing items

  The thread has executed a command. Some freeing of items done during this state involves the query cache. This state is usually followed by cleaning up.

•  Flushing tables

  The thread is executing FLUSH TABLES and is waiting for all threads to close their tables.

•  FULLTEXT initialization

  The server is preparing to perform a natural-language full-text search.

•  init

  This occurs before the initialization of ALTER TABLE, DELETE, INSERT, SELECT, or UPDATE statements. Actions taken by the server in this state include flushing the binary log, the InnoDB log, and some query cache cleanup operations.

  For the end state, the following operations could be happening:

  • Removing query cache entries after data in a table is changed

  • Writing an event to the binary log

  • Freeing memory buffers, including for blobs

•  Killed

  Someone has sent a KILL statement to the thread and it should abort next time it checks the kill flag. The flag is checked in each major loop in MySQL, but in some cases it might still take a short time for the thread to die. If the thread is locked by some other thread, the kill takes effect as soon as the other thread releases its lock.

•  Locked

  The query is locked by another query.

  As of MySQL 5.5.3, this state was removed because it was equivalent to the Table lock state and no longer appears in SHOW PROCESSLIST output.

•  logging slow query

  The thread is writing a statement to the slow-query log.

•  NULL

  This state is used for the SHOW PROCESSLIST state.

•  login

  The initial state for a connection thread until the client has been authenticated successfully.

•  manage keys

  The server is enabling or disabling a table index.

•  Opening tables, Opening table

  The thread is trying to open a table. This is should be very fast procedure, unless something prevents opening. For example, an ALTER TABLE or a LOCK TABLE statement can prevent opening a table until the statement is finished. It is also worth checking that your table_open_cache value is large enough.

•  optimizing

  The server is performing initial optimizations for a query.

•  preparing

  This state occurs during query optimization.

•  Purging old relay logs

  The thread is removing unneeded relay log files.

•  query end

  This state occurs after processing a query but before the freeing items state.

•  Reading from net

  The server is reading a packet from the network.

•  Removing duplicates

  The query was using SELECT DISTINCT in such a way that MySQL could not optimize away the distinct operation at an early stage. Because of this, MySQL requires an extra stage to remove all duplicated rows before sending the result to the client.

•  removing tmp table

  The thread is removing an internal temporary table after processing a SELECT statement. This state is not used if no temporary table was created.

•  rename

  The thread is renaming a table.

•  rename result table

  The thread is processing an ALTER TABLE statement, has created the new table, and is renaming it to replace the original table.

•  Reopen tables

  The thread got a lock for the table, but noticed after getting the lock that the underlying table structure changed. It has freed the lock, closed the table, and is trying to reopen it.

•  Repair by sorting

  The repair code is using a sort to create indexes.

•  Repair done

  The thread has completed a multi-threaded repair for a MyISAM table.

•  Repair with keycache

  The repair code is using creating keys one by one through the key cache. This is much slower than Repair by sorting.

•  Rolling back

  The thread is rolling back a transaction.

•  Saving state

  For MyISAM table operations such as repair or analysis, the thread is saving the new table state to the .MYI file header. State includes information such as number of rows, the AUTO_INCREMENT counter, and key distributions.

•  Searching rows for update

  The thread is doing a first phase to find all matching rows before updating them. This has to be done if the UPDATEis changing the index that is used to find the involved rows.

• Sending data

  The thread is reading and processing rows for a SELECT statement, and sending data to the client. Because operations occurring during this state tend to perform large amounts of disk access (reads), it is often the longest-running state over the lifetime of a given query.

•  setup

  The thread is beginning an ALTER TABLE operation.

•  Sorting for group

  The thread is doing a sort to satisfy a GROUP BY.

•  Sorting for order

  The thread is doing a sort to satisfy a ORDER BY.

•  Sorting index

  The thread is sorting index pages for more efficient access during a MyISAM table optimization operation.

•  Sorting result

  For a SELECT statement, this is similar to Creating sort index, but for nontemporary tables.

•  statistics

  The server is calculating statistics to develop a query execution plan. If a thread is in this state for a long time, the server is probably disk-bound performing other work.

•  System lock

  The thread is going to request or is waiting for an internal or external system lock for the table. If this state is being caused by requests for external locks and you are not using multiple mysqld servers that are accessing the sameMyISAM tables, you can disable external system locks with the --skip-external-locking option. However, external locking is disabled by default, so it is likely that this option will have no effect. For SHOW PROFILE, this state means the thread is requesting the lock (not waiting for it).

•  Table lock

  The next thread state after System lock. The thread has acquired an external lock and is going to request an internal table lock.

  This state was replaced in MySQL 5.5.6 with Waiting for table level lock.

•  update

  The thread is getting ready to start updating the table.

•  Updating

  The thread is searching for rows to update and is updating them.

•  updating main table

  The server is executing the first part of a multiple-table update. It is updating only the first table, and saving columns and offsets to be used for updating the other (reference) tables.

•  updating reference tables

  The server is executing the second part of a multiple-table update and updating the matched rows from the other tables.

•  User lock

  The thread is going to request or is waiting for an advisory lock requested with a GET_LOCK() call. For SHOW PROFILE, this state means the thread is requesting the lock (not waiting for it).

•  User sleep

  The thread has invoked a SLEEP() call.

•  Waiting for all running commits to finish

  A statement that causes an explicit or implicit commit is waiting for release of a read lock. This state was removed in MySQL 5.5.8; Waiting for commit lock is used instead.

•  Waiting for commit lock

  A statement that causes an explicit or implicit commit is waiting for release of a read lock or FLUSH TABLES WITH READ LOCK is waiting for a commit lock. This state was added in MySQL 5.5.8.

•  Waiting for global read lock

  FLUSH TABLES WITH READ LOCK is waiting for a global read lock or the global read_only system variable is being set.

•  Waiting for release of readlock

  The thread is waiting for a global read lock obtained by another thread (with FLUSH TABLES WITH READ LOCK) to be released. This state was removed in MySQL 5.5.8; Waiting for global read lock or Waiting for commit lock are used instead.

•  Waiting for tables, Waiting for table, Waiting for table flush

  The thread got a notification that the underlying structure for a table has changed and it needs to reopen the table to get the new structure. However, to reopen the table, it must wait until all other threads have closed the table in question.

  This notification takes place if another thread has used FLUSH TABLES or one of the following statements on the table in question: FLUSH TABLES tbl_name, ALTER TABLE, RENAME TABLE, REPAIR TABLE, ANALYZE TABLE, orOPTIMIZE TABLE.

  In MySQL 5.5.6, Waiting for table was replaced with Waiting for table flush.

•  Waiting for lock_type lock

  The server is waiting to acquire a lock, where lock_type indicates the type of lock:

  • Waiting for event metadata lock (added in MySQL 5.5.8)

  • Waiting for global metadata lock (replaced by Waiting for global read lock in MySQL 5.5.8)

  • Waiting for global read lock (added in MySQL 5.5.8)

  • Waiting for schema metadata lock

  • Waiting for stored function metadata lock

  • Waiting for stored procedure metadata lock

  • Waiting for table level lock

  • Waiting for table metadata lock

  • Waiting for trigger metadata lock (added in MySQL 5.5.8)

•  Waiting on cond

  A generic state in which the thread is waiting for a condition to become true. No specific state information is available.

•  Waiting to get readlock

  The thread has issued a FLUSH TABLES WITH READ LOCK statement to obtain a global read lock and is waiting to obtain the lock. This state was removed in MySQL 5.5.8; Waiting for global read lock is used instead.

•  Writing to net

  The server is writing a packet to the network.