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7.5.6.2. 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, you should 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 (see
Section 7.5.10, “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
, or
UPDATE
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. 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.
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.
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.
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.
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
UPDATE
is changing the index that is used to find the involved rows.
Sending data
The thread is processing rows for a
SELECT
statement and also is sending data to the client.
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 same 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.
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).
Waiting for tables, Waiting for table
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
, or
OPTIMIZE TABLE
.
Waiting on cond
A generic state in which the thread is waiting for a condition to become true. No specific state information is available.
Writing to net
The server is writing a packet to the network.
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本文來自ChinaUnix博客，如果查看原文請點：http://blog.chinaunix.net/u3/111930/showart_2186554.html |
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發(fā)表于 2010-02-25 13:03
