Sending data
The thread is processing rows for a SELECT
statement and is also sending data to the client.SELECT
statement !来自MySQL手册:
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.
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.
The thread is calculating a MyISAM
table key distributions (for example, for ANALYZE TABLE
).
The thread is performing a table check operation.
The thread has processed one command and is preparing to free memory and reset certain state variables.
Means that 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.
The thread is converting an internal temporary table from a MEMORY
table to an on-disk MyISAM
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.
If a statement has different ORDER BY
and GROUP BY
criteria, the rows are sorted by group and copied to a temporary table.
The server is copying to a temporary table in memory.
The server is copying to a temporary table on disk. The temporary result set was larger than tmp_table_size
and the thread is changing the temporary table from in-memory to disk-based format to save memory.
The thread is processing ALTER TABLE ... ENABLE KEYS
for a MyISAM
table.
The thread is processing a SELECT
that is resolved using an internal temporary table.
The thread is creating a table. This includes creation of temporary tables.
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
.
The server is executing the first part of a multiple-table delete. It is deleting only from the first table, and saving fields 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.
The thread is processing an ALTER TABLE ... DISCARD TABLESPACE
or ALTER TABLE ... IMPORT TABLESPACE
statement.
This occurs at the end but before the cleanup of ALTER TABLE
, CREATE VIEW
, DELETE
, INSERT
, SELECT
, or UPDATE
statements.
The thread is executing statements in the value of the init_command
system variable.
The thread has executed a command. This state is usually followed by cleaning up
.
The thread is executing FLUSH TABLES
and is waiting for all threads to close their tables.
The server is preparing to perform a natural-language full-text search.
This occurs before the initialization of ALTER TABLE
, DELETE
, INSERT
, SELECT
, or UPDATE
statements.
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.
The query is locked by another query.
The thread is writing a statement to the slow-query log.
The initial state for a connection thread until the client has been authenticated successfully.
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.
This state occurs during query optimization.
The thread is removing unneeded relay log files.
This state occurs after processing a query but before the freeing items
state.
The server is reading a packet from the network.
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.
The thread is removing an internal temporary table after processing a SELECT
statement. This state is not used if no temporary table was created.
The thread is renaming a table.
The thread is processing an ALTER TABLE
statement, has created the new table, and is renaming it to replace the original table.
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.
The repair code is using a sort to create indexes.
The thread has completed a multi-threaded repair for a MyISAM
table.
The repair code is using creating keys one by one through the key cache. This is much slower than Repair by sorting
.
The thread is rolling back a transaction.
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.
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.
The thread is beginning an ALTER TABLE
operation.
The thread is doing a sort to satisfy a GROUP BY
.
The thread is doing a sort to satisfy a ORDER BY
.
The thread is sorting index pages for more efficient access during a MyISAM
table optimization operation.
For a SELECT
statement, this is similar to Creating sort index
, but for non-temporary tables.
The server is calculating statistics to develop a query execution plan.
The thread is going to request or is waiting for an external system lock for the table. If you are not using multiple mysqld servers that are accessing the same tables, you can disable system locks with the --skip-external-locking
option.
The next thread state after System lock
. The thread has acquired an external lock and is going to request an internal table lock.
The thread is searching for rows to update and is updating them.
The server is executing the first part of a multiple-table update. It is updating only the first table, and saving fields and offsets to be used for updating the other (reference) tables.
The server is executing the second part of a multiple-table update and updating the matched rows from the other tables.
The thread is going to request or is waiting for an advisory lock requested with a GET_LOCK()
call.
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
.
A generic state in which the the thread is waiting for a condition to become true. No specific state information is available.
The server is writing a packet to the network
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