MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
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.
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.
The server is in the process of executing an in-place
ALTER TABLE
.
The thread is calculating a MyISAM
table
key distributions (for example, for
ANALYZE TABLE
).
The thread is checking whether the server has the required privileges to execute the statement.
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.
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.
committing alter table to storage engine
The server has finished an in-place
ALTER TABLE
and is committing
the result.
The thread is converting an internal temporary table from a
MEMORY
table to an on-disk 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.
For a thread in this state, the Performance Schema can be used to obtain about the progress of the copy operation. See Section 29.12.5, “Performance Schema Stage Event Tables”.
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 has become too large (see Section 10.4.4, “Internal Temporary Table Use in MySQL”). Consequently, 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 is 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 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.
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.
For the end
state, the following
operations could be happening:
Writing an event to the binary log
Freeing memory buffers, including for blobs
The thread has begun executing a statement.
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 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. Actions
taken by the server in this state include flushing the
binary log and the InnoDB
log.
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 thread is trying to lock a system table (for example, a time zone or log table).
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 server is enabling or disabling a table index.
The thread is trying to open a system table (for example, a time zone or log 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.
For system tables, the Opening system
tables
state is used instead.
The server is performing initial optimizations for a query.
This state occurs during query optimization.
The server is preparing to execute an in-place
ALTER TABLE
.
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 client.
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 multithreaded 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
This state is now included in the
Executing
state.
The server is writing a packet 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 an 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 nontemporary tables.
The first stage at the beginning of statement execution.
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.
The thread has called mysql_lock_tables()
and the thread state has not been updated since. This is a
very general state that can occur for many reasons.
For example, the thread is going to request or is waiting
for an internal or external system lock for the table. This
can occur when InnoDB
waits for
a table-level lock during execution of
LOCK TABLES
. If this state is
being caused by requests for external locks and you are not
using multiple mysqld servers that are
accessing the same MyISAM
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 has no effect. For
SHOW PROFILE
, this state
means the thread is requesting the lock (not waiting for
it).
For system tables, the Locking system
tables
state is used instead.
The thread is getting ready to start updating the table.
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 columns 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. For
SHOW PROFILE
, this state
means the thread is requesting the lock (not waiting for
it).
The thread has invoked a
SLEEP()
call.
FLUSH TABLES WITH READ LOCK
is waiting for a commit lock.
The thread is waiting for a transaction to commit versus other parts of query processing.
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
.
The thread is executing FLUSH
TABLES
and is waiting for all threads to close
their tables, or 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
.
The server is waiting to acquire a
THR_LOCK
lock or a lock from the metadata
locking subsystem, where
lock_type
indicates the type of
lock.
This state indicates a wait for a
THR_LOCK
:
Waiting for table level lock
These states indicate a wait for a metadata lock:
Waiting for event metadata lock
Waiting for global read lock
Waiting for schema metadata lock
Waiting for stored function metadata
lock
Waiting for stored procedure metadata
lock
Waiting for table metadata lock
Waiting for trigger metadata lock
For information about table lock indicators, see Section 10.11.1, “Internal Locking Methods”. For information about metadata locking, see Section 10.11.4, “Metadata Locking”. To see which locks are blocking lock requests, use the Performance Schema lock tables described at Section 29.12.13, “Performance Schema Lock Tables”.
A generic state in which 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.