MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
The MySQL server maintains many status variables that provide
information about its operation. You can view these variables and
their values by using the SHOW [GLOBAL | SESSION]
STATUS statement (see Section 13.7.6.35, “SHOW STATUS Syntax”).
The optional GLOBAL keyword aggregates the
values over all connections, and SESSION shows
the values for the current connection.
mysql> SHOW GLOBAL STATUS;
+-----------------------------------+------------+
| Variable_name | Value |
+-----------------------------------+------------+
| Aborted_clients | 0 |
| Aborted_connects | 0 |
| Bytes_received | 155372598 |
| Bytes_sent | 1176560426 |
...
| Connections | 30023 |
| Created_tmp_disk_tables | 0 |
| Created_tmp_files | 3 |
| Created_tmp_tables | 2 |
...
| Threads_created | 217 |
| Threads_running | 88 |
| Uptime | 1389872 |
+-----------------------------------+------------+
Many status variables are reset to 0 by the
FLUSH STATUS statement.
This section provides a description of each status variable. For a status variable summary, see Section 5.1.6, “Server Status Variable Reference”.
The status variables have the following meanings.
The number of connections that were aborted because the client died without closing the connection properly. See Section B.4.2.10, “Communication Errors and Aborted Connections”.
The number of failed attempts to connect to the MySQL server. See Section B.4.2.10, “Communication Errors and Aborted Connections”.
For additional connection-related information, check the
Connection_errors_status variables and thexxxhost_cachetable.The number of transactions that used the temporary binary log cache but that exceeded the value of
binlog_cache_sizeand used a temporary file to store statements from the transaction.The number of nontransactional statements that caused the binary log transaction cache to be written to disk is tracked separately in the
Binlog_stmt_cache_disk_usestatus variable.The number of cached privilege objects. Each object is the privilege combination of a user and its active roles.
The number of transactions that used the binary log cache.
The number of nontransaction statements that used the binary log statement cache but that exceeded the value of
binlog_stmt_cache_sizeand used a temporary file to store those statements.The number of nontransactional statements that used the binary log statement cache.
The number of bytes received from all clients.
The number of bytes sent to all clients.
Caching_sha2_password_rsa_public_keyThe public key used by the
caching_sha2_passwordauthentication plugin for RSA key pair-based password exchange. The value is nonempty only if the server successfully initializes the private and public keys in the files named by thecaching_sha2_password_private_key_pathandcaching_sha2_password_public_key_pathsystem variables. The value ofCaching_sha2_password_rsa_public_keycomes from the latter file.The
Com_statement counter variables indicate the number of times eachxxxxxxstatement has been executed. There is one status variable for each type of statement. For example,Com_deleteandCom_updatecountDELETEandUPDATEstatements, respectively.Com_delete_multiandCom_update_multiare similar but apply toDELETEandUPDATEstatements that use multiple-table syntax.The discussion at the beginning of this section indicates how to relate these statement-counting status variables to other such variables.
All of the
Com_stmt_variables are increased even if a prepared statement argument is unknown or an error occurred during execution. In other words, their values correspond to the number of requests issued, not to the number of requests successfully completed.xxxThe
Com_stmt_status variables are as follows:xxxCom_stmt_prepareCom_stmt_executeCom_stmt_fetchCom_stmt_send_long_dataCom_stmt_resetCom_stmt_close
Those variables stand for prepared statement commands. Their names refer to the
COM_command set used in the network layer. In other words, their values increase whenever prepared statement API calls such as mysql_stmt_prepare(), mysql_stmt_execute(), and so forth are executed. However,xxxCom_stmt_prepare,Com_stmt_executeandCom_stmt_closealso increase forPREPARE,EXECUTE, orDEALLOCATE PREPARE, respectively. Additionally, the values of the older statement counter variablesCom_prepare_sql,Com_execute_sql, andCom_dealloc_sqlincrease for thePREPARE,EXECUTE, andDEALLOCATE PREPAREstatements.Com_stmt_fetchstands for the total number of network round-trips issued when fetching from cursors.Com_stmt_reprepareindicates the number of times statements were automatically reprepared by the server, for example, after metadata changes to tables or views referred to by the statement. A reprepare operation incrementsCom_stmt_reprepare, and alsoCom_stmt_prepare.Com_explain_otherindicates the number ofEXPLAIN FOR CONNECTIONstatements executed. See Section 8.8.4, “Obtaining Execution Plan Information for a Named Connection”.Com_change_repl_filterindicates the number ofCHANGE REPLICATION FILTERstatements executed.Whether the client connection uses compression in the client/server protocol.
These variables provide information about errors that occur during the client connection process. They are global only and represent error counts aggregated across connections from all hosts. These variables track errors not accounted for by the host cache (see Section 8.12.4.2, “DNS Lookup Optimization and the Host Cache”), such as errors that are not associated with TCP connections, occur very early in the connection process (even before an IP address is known), or are not specific to any particular IP address (such as out-of-memory conditions).
The number of errors that occurred during calls to
accept()on the listening port.The number of connections refused due to internal errors in the server, such as failure to start a new thread or an out-of-memory condition.
Connection_errors_max_connectionsThe number of connections refused because the server
max_connectionslimit was reached.Connection_errors_peer_addressThe number of errors that occurred while searching for connecting client IP addresses.
The number of errors that occurred during calls to
select()orpoll()on the listening port. (Failure of this operation does not necessarily means a client connection was rejected.)The number of connections refused by the
libwraplibrary.
The number of connection attempts (successful or not) to the MySQL server.
The number of internal on-disk temporary tables created by the server while executing statements.
If an internal temporary table is created initially as an in-memory table but becomes too large, MySQL automatically converts it to an on-disk table. The maximum size for in-memory temporary tables is the minimum of the
tmp_table_sizeandmax_heap_table_sizevalues. IfCreated_tmp_disk_tablesis large, you may want to increase thetmp_table_sizeormax_heap_table_sizevalue to lessen the likelihood that internal temporary tables in memory will be converted to on-disk tables.You can compare the number of internal on-disk temporary tables created to the total number of internal temporary tables created by comparing the values of the
Created_tmp_disk_tablesandCreated_tmp_tablesvariables.See also Section 8.4.4, “Internal Temporary Table Use in MySQL”.
How many temporary files mysqld has created.
The number of internal temporary tables created by the server while executing statements.
You can compare the number of internal on-disk temporary tables created to the total number of internal temporary tables created by comparing the values of the
Created_tmp_disk_tablesandCreated_tmp_tablesvariables.See also Section 8.4.4, “Internal Temporary Table Use in MySQL”.
Each invocation of the
SHOW STATUSstatement uses an internal temporary table and increments the globalCreated_tmp_tablesvalue.The active
ssl_cavalue in the SSL context that the server uses for new connections. This context value may differ from the currentssl_casystem variable value if the system variable has been changed butALTER INSTANCE RELOAD TLShas not subsequently been executed to reconfigure the SSL context from the context-related system variable values and update the corresponding status variables. (This potential difference in values applies to each corresponding pair of context-related system and status variables. See Server-Side Runtime Configuration for Encrypted Connections.)This variable was added in MySQL 8.0.16.
The active
ssl_capathvalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
The active
ssl_certvalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
The active
ssl_ciphervalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
The active
tls_ciphersuitesvalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
The active
ssl_crlvalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
The active
ssl_crlpathvalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
The active
ssl_keyvalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
The active
tls_versionvalue in the SSL context that the server uses for new connections. For notes about the relationship between this status variable and its corresponding system variable, see the description ofCurrent_tls_ca.This variable was added in MySQL 8.0.16.
This status variable is deprecated (because
DELAYEDinserts are not supported), and will be removed in a future release.This status variable is deprecated (because
DELAYEDinserts are not supported), and will be removed in a future release.This status variable is deprecated (because
DELAYEDinserts are not supported), and will be removed in a future release.The result of the most recent assignment to the
dragnet.log_error_filter_rulessystem variable, empty if no such assignment has occurred.This variable was added in MySQL 8.0.12.
The number of times the server flushes tables, whether because a user executed a
FLUSH TABLESstatement or due to internal server operation. It is also incremented by receipt of aCOM_REFRESHpacket. This is in contrast toCom_flush, which indicates how manyFLUSHstatements have been executed, whetherFLUSH TABLES,FLUSH LOGS, and so forth.group_replication_primary_memberShows the primary member's UUID when the group is operating in single-primary mode. If the group is operating in multi-primary mode, shows an empty string.
The
group_replication_primary_memberstatus variable has been deprecated and is scheduled to be removed in a future version.The number of internal
COMMITstatements.The number of times that rows have been deleted from tables.
The server increments this variable for each call to its
external_lock()function, which generally occurs at the beginning and end of access to a table instance. There might be differences among storage engines. This variable can be used, for example, to discover for a statement that accesses a partitioned table how many partitions were pruned before locking occurred: Check how much the counter increased for the statement, subtract 2 (2 calls for the table itself), then divide by 2 to get the number of partitions locked.The number of times the server uses a storage engine's own Multi-Range Read implementation for table access.
A counter for the prepare phase of two-phase commit operations.
The number of times the first entry in an index was read. If this value is high, it suggests that the server is doing a lot of full index scans (for example,
SELECT col1 FROM foo, assuming thatcol1is indexed).The number of requests to read a row based on a key. If this value is high, it is a good indication that your tables are properly indexed for your queries.
The number of requests to read the last key in an index. With
ORDER BY, the server will issue a first-key request followed by several next-key requests, whereas withORDER BY DESC, the server will issue a last-key request followed by several previous-key requests.The number of requests to read the next row in key order. This value is incremented if you are querying an index column with a range constraint or if you are doing an index scan.
The number of requests to read the previous row in key order. This read method is mainly used to optimize
ORDER BY ... DESC.The number of requests to read a row based on a fixed position. This value is high if you are doing a lot of queries that require sorting of the result. You probably have a lot of queries that require MySQL to scan entire tables or you have joins that do not use keys properly.
The number of requests to read the next row in the data file. This value is high if you are doing a lot of table scans. Generally this suggests that your tables are not properly indexed or that your queries are not written to take advantage of the indexes you have.
The number of requests for a storage engine to perform a rollback operation.
The number of requests for a storage engine to place a savepoint.
The number of requests for a storage engine to roll back to a savepoint.
The number of requests to update a row in a table.
The number of requests to insert a row in a table.
Innodb_available_undo_logswas removed in MySQL 8.0.2. The number of available rollback segments per tablespace may be retrieved usingSHOW VARIABLES LIKE 'innodb_rollback_segments';Innodb_buffer_pool_dump_statusThe progress of an operation to record the pages held in the
InnoDBbuffer pool, triggered by the setting ofinnodb_buffer_pool_dump_at_shutdownorinnodb_buffer_pool_dump_now.For related information and examples, see Section 15.8.3.7, “Saving and Restoring the Buffer Pool State”.
Innodb_buffer_pool_load_statusThe progress of an operation to warm up the
InnoDBbuffer pool by reading in a set of pages corresponding to an earlier point in time, triggered by the setting ofinnodb_buffer_pool_load_at_startuporinnodb_buffer_pool_load_now. If the operation introduces too much overhead, you can cancel it by settinginnodb_buffer_pool_load_abort.For related information and examples, see Section 15.8.3.7, “Saving and Restoring the Buffer Pool State”.
The total number of bytes in the
InnoDBbuffer pool containing data. The number includes both dirty and clean pages. For more accurate memory usage calculations than withInnodb_buffer_pool_pages_data, when compressed tables cause the buffer pool to hold pages of different sizes.The number of pages in the
InnoDBbuffer pool containing data. The number includes both dirty and clean pages. When using compressed tables, the reportedInnodb_buffer_pool_pages_datavalue may be larger thanInnodb_buffer_pool_pages_total(Bug #59550).Innodb_buffer_pool_bytes_dirtyThe total current number of bytes held in dirty pages in the
InnoDBbuffer pool. For more accurate memory usage calculations than withInnodb_buffer_pool_pages_dirty, when compressed tables cause the buffer pool to hold pages of different sizes.Innodb_buffer_pool_pages_dirtyThe current number of dirty pages in the
InnoDBbuffer pool.Innodb_buffer_pool_pages_flushedThe number of requests to flush pages from the
InnoDBbuffer pool.The number of free pages in the
InnoDBbuffer pool.Innodb_buffer_pool_pages_latchedThe number of latched pages in the
InnoDBbuffer pool. These are pages currently being read or written, or that cannot be flushed or removed for some other reason. Calculation of this variable is expensive, so it is available only when theUNIV_DEBUGsystem is defined at server build time.The number of pages in the
InnoDBbuffer pool that are busy because they have been allocated for administrative overhead, such as row locks or the adaptive hash index. This value can also be calculated asInnodb_buffer_pool_pages_total−Innodb_buffer_pool_pages_free−Innodb_buffer_pool_pages_data. When using compressed tables,Innodb_buffer_pool_pages_miscmay report an out-of-bounds value (Bug #59550).Innodb_buffer_pool_pages_totalThe total size of the
InnoDBbuffer pool, in pages. When using compressed tables, the reportedInnodb_buffer_pool_pages_datavalue may be larger thanInnodb_buffer_pool_pages_total(Bug #59550)The number of pages read into the
InnoDBbuffer pool by the read-ahead background thread.Innodb_buffer_pool_read_ahead_evictedThe number of pages read into the
InnoDBbuffer pool by the read-ahead background thread that were subsequently evicted without having been accessed by queries.Innodb_buffer_pool_read_ahead_rndThe number of “random” read-aheads initiated by
InnoDB. This happens when a query scans a large portion of a table but in random order.Innodb_buffer_pool_read_requestsThe number of logical read requests.
The number of logical reads that
InnoDBcould not satisfy from the buffer pool, and had to read directly from disk.Innodb_buffer_pool_resize_statusThe status of an operation to resize the
InnoDBbuffer pool dynamically, triggered by setting theinnodb_buffer_pool_sizeparameter dynamically. Theinnodb_buffer_pool_sizeparameter is dynamic, which allows you to resize the buffer pool without restarting the server. See Configuring InnoDB Buffer Pool Size Online for related information.Normally, writes to the
InnoDBbuffer pool happen in the background. WhenInnoDBneeds to read or create a page and no clean pages are available,InnoDBflushes some dirty pages first and waits for that operation to finish. This counter counts instances of these waits. Ifinnodb_buffer_pool_sizehas been set properly, this value should be small.Innodb_buffer_pool_write_requestsThe number of writes done to the
InnoDBbuffer pool.The number of
fsync()operations so far. The frequency offsync()calls is influenced by the setting of theinnodb_flush_methodconfiguration option.The current number of pending
fsync()operations. The frequency offsync()calls is influenced by the setting of theinnodb_flush_methodconfiguration option.The current number of pending reads.
The current number of pending writes.
The amount of data read since the server was started (in bytes).
The total number of data reads (OS file reads).
The total number of data writes.
The amount of data written so far, in bytes.
The number of pages that have been written to the doublewrite buffer. See Section 15.11.1, “InnoDB Disk I/O”.
The number of doublewrite operations that have been performed. See Section 15.11.1, “InnoDB Disk I/O”.
Indicates whether the server was built with atomic instructions.
The number of times that the log buffer was too small and a wait was required for it to be flushed before continuing.
The number of write requests for the
InnoDBredo log.The number of physical writes to the
InnoDBredo log file.The number of files
InnoDBcurrently holds open.The number of
fsync()writes done to theInnoDBredo log files.The number of pending
fsync()operations for theInnoDBredo log files.The number of pending writes to the
InnoDBredo log files.The number of bytes written to the
InnoDBredo log files.InnoDBpage size (default 16KB). Many values are counted in pages; the page size enables them to be easily converted to bytes.The number of pages created by operations on
InnoDBtables.The number of pages read from the
InnoDBbuffer pool by operations onInnoDBtables.The number of pages written by operations on
InnoDBtables.The number of row locks currently being waited for by operations on
InnoDBtables.The total time spent in acquiring row locks for
InnoDBtables, in milliseconds.The average time to acquire a row lock for
InnoDBtables, in milliseconds.The maximum time to acquire a row lock for
InnoDBtables, in milliseconds.The number of times operations on
InnoDBtables had to wait for a row lock.The number of rows deleted from
InnoDBtables.The number of rows inserted into
InnoDBtables.The number of rows read from
InnoDBtables.The number of rows updated in
InnoDBtables.Innodb_truncated_status_writesThe number of times output from the
SHOW ENGINE INNODB STATUSstatement has been truncated.The number of key blocks in the
MyISAMkey cache that have changed but have not yet been flushed to disk.The number of unused blocks in the
MyISAMkey cache. You can use this value to determine how much of the key cache is in use; see the discussion ofkey_buffer_sizein Section 5.1.8, “Server System Variables”.The number of used blocks in the
MyISAMkey cache. This value is a high-water mark that indicates the maximum number of blocks that have ever been in use at one time.The number of requests to read a key block from the
MyISAMkey cache.The number of physical reads of a key block from disk into the
MyISAMkey cache. IfKey_readsis large, then yourkey_buffer_sizevalue is probably too small. The cache miss rate can be calculated asKey_reads/Key_read_requests.The number of requests to write a key block to the
MyISAMkey cache.The number of physical writes of a key block from the
MyISAMkey cache to disk.The total cost of the last compiled query as computed by the query optimizer. This is useful for comparing the cost of different query plans for the same query. The default value of 0 means that no query has been compiled yet. The default value is 0.
Last_query_costhas session scope.In MySQL 8.0.16 and later, this variable shows the cost of queries that have multiple query blocks, summing the cost estimates of each query block, estimating how many times non-cacheable subqueries are executed, and multiplying the cost of those query blocks by the number of subquery executions. (Bug #92766, Bug #28786951) Prior to MySQL 8.0.16,
Last_query_costwas computed accurately only for simple, “flat” queries, but not for complex queries such as those containing subqueries orUNION. (For the latter, the value was set to 0.)The number of iterations the query optimizer made in execution plan construction for the previous query.
Last_query_costhas session scope.The number of attempts to connect to locked user accounts. For information about account locking and unlocking, see Section 6.2.19, “Account Locking”.
The number of
SELECTstatements for which the execution timeout was exceeded.The number of
SELECTstatements for which a nonzero execution timeout was set. This includes statements that include a nonzeroMAX_EXECUTION_TIMEoptimizer hint, and statements that include no such hint but execute while the timeout indicated by themax_execution_timesystem variable is nonzero.The number of
SELECTstatements for which the attempt to set an execution timeout failed.The maximum number of connections that have been in use simultaneously since the server started.
The time at which
Max_used_connectionsreached its current value.This status variable is deprecated (because
DELAYEDinserts are not supported), and will be removed in a future release.The character set currently used by the MeCab full-text parser plugin. For related information, see Section 12.9.9, “MeCab Full-Text Parser Plugin”.
Ongoing_anonymous_transaction_countShows the number of ongoing transactions which have been marked as anonymous. This can be used to ensure that no further transactions are waiting to be processed.
Ongoing_anonymous_gtid_violating_transaction_countThis status variable is only available in debug builds. Shows the number of ongoing transactions which use
gtid_next=ANONYMOUSand that violate GTID consistency.Ongoing_automatic_gtid_violating_transaction_countThis status variable is only available in debug builds. Shows the number of ongoing transactions which use
gtid_next=AUTOMATICand that violate GTID consistency.The number of files that are open. This count includes regular files opened by the server. It does not include other types of files such as sockets or pipes. Also, the count does not include files that storage engines open using their own internal functions rather than asking the server level to do so.
The number of streams that are open (used mainly for logging).
The number of cached table definitions.
The number of tables that are open.
The number of files that have been opened with
my_open()(amysyslibrary function). Parts of the server that open files without using this function do not increment the count.The number of table definitions that have been cached.
The number of tables that have been opened. If
Opened_tablesis big, yourtable_open_cachevalue is probably too small.Performance_schema_xxxPerformance Schema status variables are listed in Section 26.16, “Performance Schema Status Variables”. These variables provide information about instrumentation that could not be loaded or created due to memory constraints.
The current number of prepared statements. (The maximum number of statements is given by the
max_prepared_stmt_countsystem variable.)This status variable was removed in MySQL 8.0.3.
This status variable was removed in MySQL 8.0.3.
This status variable was removed in MySQL 8.0.3.
This status variable was removed in MySQL 8.0.3.
This status variable was removed in MySQL 8.0.3.
This status variable was removed in MySQL 8.0.3.
This status variable was removed in MySQL 8.0.3.
This status variable was removed in MySQL 8.0.3.
The number of statements executed by the server. This variable includes statements executed within stored programs, unlike the
Questionsvariable. It does not countCOM_PINGorCOM_STATISTICScommands.The discussion at the beginning of this section indicates how to relate this statement-counting status variable to other such variables.
The number of statements executed by the server. This includes only statements sent to the server by clients and not statements executed within stored programs, unlike the
Queriesvariable. This variable does not countCOM_PING,COM_STATISTICS,COM_STMT_PREPARE,COM_STMT_CLOSE, orCOM_STMT_RESETcommands.The discussion at the beginning of this section indicates how to relate this statement-counting status variable to other such variables.
The number of semisynchronous slaves.
This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_net_avg_wait_timeThe average time in microseconds the master waited for a slave reply. This variable is always
0, is deprecated and it will be removed in a future version.This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_net_wait_timeThe total time in microseconds the master waited for slave replies. This variable is always
0, is deprecated and it will be removed in a future version.This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_net_waitsThe total number of times the master waited for slave replies.
This variable is available only if the master-side semisynchronous replication plugin is installed.
The number of times the master turned off semisynchronous replication.
This variable is available only if the master-side semisynchronous replication plugin is installed.
The number of commits that were not acknowledged successfully by a slave.
This variable is available only if the master-side semisynchronous replication plugin is installed.
Whether semisynchronous replication currently is operational on the master. The value is
ONif the plugin has been enabled and a commit acknowledgment has occurred. It isOFFif the plugin is not enabled or the master has fallen back to asynchronous replication due to commit acknowledgment timeout.This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_timefunc_failuresThe number of times the master failed when calling time functions such as
gettimeofday().This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_tx_avg_wait_timeThe average time in microseconds the master waited for each transaction.
This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_tx_wait_timeThe total time in microseconds the master waited for transactions.
This variable is available only if the master-side semisynchronous replication plugin is installed.
The total number of times the master waited for transactions.
This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_wait_pos_backtraverseThe total number of times the master waited for an event with binary coordinates lower than events waited for previously. This can occur when the order in which transactions start waiting for a reply is different from the order in which their binary log events are written.
This variable is available only if the master-side semisynchronous replication plugin is installed.
Rpl_semi_sync_master_wait_sessionsThe number of sessions currently waiting for slave replies.
This variable is available only if the master-side semisynchronous replication plugin is installed.
The number of commits that were acknowledged successfully by a slave.
This variable is available only if the master-side semisynchronous replication plugin is installed.
Whether semisynchronous replication currently is operational on the slave. This is
ONif the plugin has been enabled and the slave I/O thread is running,OFFotherwise.This variable is available only if the slave-side semisynchronous replication plugin is installed.
This variable is available if MySQL was compiled using OpenSSL (see Section 6.3.3, “SSL Library-Dependent Capabilities”). Its value is the public key used by the
sha256_passwordauthentication plugin for RSA key pair-based password exchange. The value is nonempty only if the server successfully initializes the private and public keys in the files named by thesha256_password_private_key_pathandsha256_password_public_key_pathsystem variables. The value ofRsa_public_keycomes from the latter file.For information about
sha256_password, see Section 6.4.1.2, “SHA-256 Pluggable Authentication”.Secondary_engine_execution_countFor future use. This variable was added in MySQL 8.0.13.
The number of joins that perform table scans because they do not use indexes. If this value is not 0, you should carefully check the indexes of your tables.
The number of joins that used a range search on a reference table.
The number of joins that used ranges on the first table. This is normally not a critical issue even if the value is quite large.
The number of joins without keys that check for key usage after each row. If this is not 0, you should carefully check the indexes of your tables.
The number of joins that did a full scan of the first table.
This variable is obsolete and was removed in MySQL 8.0.1. Instead, use the
HEARTBEAT_INTERVALcolumn of thereplication_connection_configurationtable.This variable is obsolete and was removed in MySQL 8.0.1. Instead, use the
LAST_HEARTBEAT_TIMESTAMPcolumn of thereplication_connection_statustable.The number of temporary tables that the slave SQL thread currently has open. If the value is greater than zero, it is not safe to shut down the slave; see Section 17.4.1.30, “Replication and Temporary Tables”. This variable reports the total count of open temporary tables for all replication channels.
This variable is obsolete and was removed in MySQL 8.0.1. Instead, use the
COUNT_RECEIVED_HEARTBEATScolumn of thereplication_connection_statustable.This variable is obsolete and was removed in MySQL 8.0.1. Instead, use the
COUNT_TRANSACTIONS_RETRIEScolumn of thereplication_applier_statustable.Slave_rows_last_search_algorithm_usedThe search algorithm that was most recently used by this slave to locate rows for row-based replication. The result shows whether the slave used indexes, a table scan, or hashing as the search algorithm for the last transaction executed on any channel.
The method used depends on the setting for the
slave_rows_search_algorithmssystem variable, and the keys that are available on the relevant table.This variable is available only for debug builds of MySQL.
This variable is obsolete and was removed in MySQL 8.0.1. Instead, use the
SERVICE_STATEcolumn of thereplication_connection_statusandreplication_applier_statustables.The number of threads that have taken more than
slow_launch_timeseconds to create.The number of queries that have taken more than
long_query_timeseconds. This counter increments regardless of whether the slow query log is enabled. For information about that log, see Section 5.4.5, “The Slow Query Log”.The number of merge passes that the sort algorithm has had to do. If this value is large, you should consider increasing the value of the
sort_buffer_sizesystem variable.The number of sorts that were done using ranges.
The number of sorted rows.
The number of sorts that were done by scanning the table.
The number of negotiates needed to establish the connection.
The number of accepted SSL connections.
The number of callback cache hits.
The current encryption cipher (empty for unencrypted connections).
The list of possible SSL ciphers (empty for non-SSL connections). If MySQL supports TLSv1.3, the value includes the possible TLSv1.3 ciphersuites. See Section 6.3.5, “Encrypted Connection Protocols and Ciphers”.
The number of SSL connection attempts to an SSL-enabled master.
The number of negotiates needed to establish the connection to an SSL-enabled master.
The SSL context verification depth (how many certificates in the chain are tested).
The SSL context verification mode.
The default SSL timeout.
The number of successful SSL connections to the server.
The number of successful slave connections to an SSL-enabled master.
The last date for which the SSL certificate is valid. To check SSL certificate expiration information, use this statement:
mysql> SHOW STATUS LIKE 'Ssl_server_not%'; +-----------------------+--------------------------+ | Variable_name | Value | +-----------------------+--------------------------+ | Ssl_server_not_after | Apr 28 14:16:39 2025 GMT | | Ssl_server_not_before | May 1 14:16:39 2015 GMT | +-----------------------+--------------------------+The first date for which the SSL certificate is valid.
The number of SSL session cache hits.
The number of SSL session cache misses.
The SSL session cache mode.
The number of SSL session cache overflows.
The SSL session cache size.
The number of SSL session cache timeouts.
How many SSL connections were reused from the cache.
Ssl_used_session_cache_entriesHow many SSL session cache entries were used.
The verification depth for replication SSL connections.
The verification mode used by the server for a connection that uses SSL. The value is a bitmask; bits are defined in the
openssl/ssl.hheader file:# define SSL_VERIFY_NONE 0x00 # define SSL_VERIFY_PEER 0x01 # define SSL_VERIFY_FAIL_IF_NO_PEER_CERT 0x02 # define SSL_VERIFY_CLIENT_ONCE 0x04SSL_VERIFY_PEERindicates that the server asks for a client certificate. If the client supplies one, the server performs verification and proceeds only if verification is successful.SSL_VERIFY_CLIENT_ONCEindicates that a request for the client certificate will be done only in the initial handshake.The SSL protocol version of the connection (for example, TLSv1). If the connection is not encrypted, the value is empty.
The number of times that a request for a table lock could be granted immediately.
The number of times that a request for a table lock could not be granted immediately and a wait was needed. If this is high and you have performance problems, you should first optimize your queries, and then either split your table or tables or use replication.
The number of hits for open tables cache lookups.
The number of misses for open tables cache lookups.
The number of overflows for the open tables cache. This is the number of times, after a table is opened or closed, a cache instance has an unused entry and the size of the instance is larger than
table_open_cache/table_open_cache_instances.For the memory-mapped implementation of the log that is used by mysqld when it acts as the transaction coordinator for recovery of internal XA transactions, this variable indicates the largest number of pages used for the log since the server started. If the product of
Tc_log_max_pages_usedandTc_log_page_sizeis always significantly less than the log size, the size is larger than necessary and can be reduced. (The size is set by the--log-tc-sizeoption. This variable is unused: It is unneeded for binary log-based recovery, and the memory-mapped recovery log method is not used unless the number of storage engines that are capable of two-phase commit and that support XA transactions is greater than one. (InnoDBis the only applicable engine.)The page size used for the memory-mapped implementation of the XA recovery log. The default value is determined using
getpagesize(). This variable is unused for the same reasons as described forTc_log_max_pages_used.For the memory-mapped implementation of the recovery log, this variable increments each time the server was not able to commit a transaction and had to wait for a free page in the log. If this value is large, you might want to increase the log size (with the
--log-tc-sizeoption). For binary log-based recovery, this variable increments each time the binary log cannot be closed because there are two-phase commits in progress. (The close operation waits until all such transactions are finished.)The number of threads in the thread cache.
The number of currently open connections.
The number of threads created to handle connections. If
Threads_createdis big, you may want to increase thethread_cache_sizevalue. The cache miss rate can be calculated asThreads_created/Connections.The number of threads that are not sleeping.
The number of seconds that the server has been up.
The number of seconds since the most recent
FLUSH STATUSstatement.