16.1.4.4. Binary Log Options and Variables

--binlog-row-event-max-size=N

Specify the maximum size of a row-based binary log event, in bytes. Rows are grouped into events smaller than this size if possible. The value should be a multiple of 256. The default is 8192. See Section 16.1.2, "Replication Formats".

--log-bin[=base_name]

Enable binary logging. The server logs all statements that change data to the binary log, which is used for backup and replication. See Section 5.2.4, "The Binary Log".

The option value, if given, is the basename for the log sequence. The server creates binary log files in sequence by adding a numeric suffix to the basename. It is recommended that you specify a basename (see Section C.5.8, "Known Issues in MySQL", for the reason). Otherwise, MySQL uses host_name-bin as the basename.

When the server reads an entry from the index file, it checks whether the entry contains a relative path, and if it does, the relative part of the path in replaced with the absolute path set using the --log-bin option. An absolute path remains unchanged; in such a case, the index must be edited manually to enable the new path or paths to be used. (In older versions of MySQL, manual intervention was required whenever relocating the binary log or relay log files.) (Bug #11745230, Bug #12133)

Setting this option causes the log_bin system variable to be set to ON (or 1), and not to the basename. The binary log filename (with path) is available as the log_bin_basename system variable.

--log-bin-index[=file_name]

The index file for binary log file names. See Section 5.2.4, "The Binary Log". If you omit the file name, and if you did not specify one with --log-bin, MySQL uses host_name-bin.index as the file name.

--log-bin-trust-function-creators[={0|1}]

This option sets the corresponding log_bin_trust_function_creators system variable. If no argument is given, the option sets the variable to 1. log_bin_trust_function_creators affects how MySQL enforces restrictions on stored function and trigger creation. See Section 18.7, "Binary Logging of Stored Programs".

--log-bin-use-v1-row-events[={0|1}]

MySQL 5.7 uses Version 2 binary log row events, which cannot be read by MySQL Server releases prior to MySQL 5.6.6. Setting this option to 1 causes mysqld to write the binary log using Version 1 logging events, which is the only version of binary log events used in previous releases, and thus produce binary logs that can be read by older slaves. Setting --log-bin-use-v1-row-events to 0 (the default) causes mysqld to use Version 2 binary log events.

The value used for this option can be obtained from the read-only log_bin_use_v1_row_events system variable.

--log-short-format

Log less information to the binary log and slow query log, if they have been activated.

--binlog-do-db=db_name

This option affects binary logging in a manner similar to the way that --replicate-do-db affects replication.

The effects of this option depend on whether the statement-based or row-based logging format is in use, in the same way that the effects of --replicate-do-db depend on whether statement-based or row-based replication is in use. You should keep in mind that the format used to log a given statement may not necessarily be the same as that indicated by the value of binlog_format. For example, DDL statements such as CREATE TABLE and ALTER TABLE are always logged as statements, without regard to the logging format in effect, so the following statement-based rules for --binlog-do-db always apply in determining whether or not the statement is logged.

Statement-based logging. Only those statements are written to the binary log where the default database (that is, the one selected by USE) is db_name. To specify more than one database, use this option multiple times, once for each database; however, doing so does not cause cross-database statements such as UPDATE some_db.some_table SET foo='bar' to be logged while a different database (or no database) is selected.

An example of what does not work as you might expect when using statement-based logging: If the server is started with --binlog-do-db=sales and you issue the following statements, the UPDATE statement is not logged:

USE prices;UPDATE sales.january SET amount=amount+1000;

The main reason for this "just check the default database" behavior is that it is difficult from the statement alone to know whether it should be replicated (for example, if you are using multiple-table DELETE statements or multiple-table UPDATE statements that act across multiple databases). It is also faster to check only the default database rather than all databases if there is no need.

Another case which may not be self-evident occurs when a given database is replicated even though it was not specified when setting the option. If the server is started with --binlog-do-db=sales, the following UPDATE statement is logged even though prices was not included when setting --binlog-do-db:

          USE sales;UPDATE prices.discounts SET percentage = percentage + 10;

Because sales is the default database when the UPDATE statement is issued, the UPDATE is logged.

Row-based logging. Logging is restricted to database db_name. Only changes to tables belonging to db_name are logged; the default database has no effect on this. Suppose that the server is started with --binlog-do-db=sales and row-based logging is in effect, and then the following statements are executed:

USE prices;UPDATE sales.february SET amount=amount+100;

The changes to the february table in the sales database are logged in accordance with the UPDATE statement; this occurs whether or not the USE statement was issued. However, when using the row-based logging format and --binlog-do-db=sales, changes made by the following UPDATE are not logged:

USE prices;UPDATE prices.march SET amount=amount-25;

Even if the USE prices statement were changed to USE sales, the UPDATE statement's effects would still not be written to the binary log.

Another important difference in --binlog-do-db handling for statement-based logging as opposed to the row-based logging occurs with regard to statements that refer to multiple databases. Suppose that the server is started with --binlog-do-db=db1, and the following statements are executed:

USE db1;UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

If you are using statement-based logging, the updates to both tables are written to the binary log. However, when using the row-based format, only the changes to table1 are logged; table2 is in a different database, so it is not changed by the UPDATE. Now suppose that, instead of the USE db1 statement, a USE db4 statement had been used:

USE db4;UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

In this case, the UPDATE statement is not written to the binary log when using statement-based logging. However, when using row-based logging, the change to table1 is logged, but not that to table2—in other words, only changes to tables in the database named by --binlog-do-db are logged, and the choice of default database has no effect on this behavior.

--binlog-ignore-db=db_name

This option affects binary logging in a manner similar to the way that --replicate-ignore-db affects replication.

The effects of this option depend on whether the statement-based or row-based logging format is in use, in the same way that the effects of --replicate-ignore-db depend on whether statement-based or row-based replication is in use. You should keep in mind that the format used to log a given statement may not necessarily be the same as that indicated by the value of binlog_format. For example, DDL statements such as CREATE TABLE and ALTER TABLE are always logged as statements, without regard to the logging format in effect, so the following statement-based rules for --binlog-ignore-db always apply in determining whether or not the statement is logged.

Statement-based logging. Tells the server to not log any statement where the default database (that is, the one selected by USE) is db_name.

Prior to MySQL 5.7.2, this option caused any statements containing fully qualified table names not to be logged if there was no default database specified (that is, when SELECT DATABASE() returned NULL). In MySQL 5.7.2 and later, when there is no default database, no --binlog-ignore-db options are applied, and such statements are always logged. (Bug #11829838, Bug #60188)

Row-based format. Tells the server not to log updates to any tables in the database db_name. The current database has no effect.

When using statement-based logging, the following example does not work as you might expect. Suppose that the server is started with --binlog-ignore-db=sales and you issue the following statements:

USE prices;UPDATE sales.january SET amount=amount+1000;

The UPDATE statement is logged in such a case because --binlog-ignore-db applies only to the default database (determined by the USE statement). Because the sales database was specified explicitly in the statement, the statement has not been filtered. However, when using row-based logging, the UPDATE statement's effects are not written to the binary log, which means that no changes to the sales.january table are logged; in this instance, --binlog-ignore-db=sales causes all changes made to tables in the master's copy of the sales database to be ignored for purposes of binary logging.

To specify more than one database to ignore, use this option multiple times, once for each database. Because database names can contain commas, the list will be treated as the name of a single database if you supply a comma-separated list.

You should not use this option if you are using cross-database updates and you do not want these updates to be logged.

--binlog-checksum={NONE|CRC32}

Enabling this option causes the master to write checksums for events written to the binary log. Set to NONE to disable, or the name of the algorithm to be used for generating checksums; currently, only CRC32 checksums are supported, and CRC32 is the default.

--master-verify-checksum={0|1}

Enabling this option causes the master to verify events from the binary log using checksums, and to stop with an error in the event of a mismatch. Disabled by default.

--max-binlog-dump-events=N

This option is used internally by the MySQL test suite for replication testing and debugging.

--sporadic-binlog-dump-fail

This option is used internally by the MySQL test suite for replication testing and debugging.

--binlog-rows-query-log-events

This option enables binlog_rows_query_log_events.

log_bin

Whether the binary log is enabled. If the --log-bin option is used, then the value of this variable is ON; otherwise it is OFF. This variable reports only on the status of binary logging (enabled or disabled); it does not actually report the value to which --log-bin is set.

See Section 5.2.4, "The Binary Log".

log_slave_updates

Whether updates received by a slave server from a master server should be logged to the slave's own binary log. Binary logging must be enabled on the slave for this variable to have any effect. See Section 16.1.4, "Replication and Binary Logging Options and Variables".

binlog_cache_size

The size of the cache to hold changes to the binary log during a transaction. A binary log cache is allocated for each client if the server supports any transactional storage engines and if the server has the binary log enabled (--log-bin option). If you often use large transactions, you can increase this cache size to get better performance. The Binlog_cache_use and Binlog_cache_disk_use status variables can be useful for tuning the size of this variable. See Section 5.2.4, "The Binary Log".

binlog_cache_size sets the size for the transaction cache only; the size of the statement cache is governed by the binlog_stmt_cache_size system variable.

binlog_checksum

When enabled, this variable causes the master to write a checksum for each event in the binary log. binlog_checksum supports the values NONE (disabled) and CRC32. The default is CRC32.

When binlog_checksum is disabled (value NONE), the server verifies that it is writing only complete events to the binary log by writing and checking the event length (rather than a checksum) for each event.

Changing the value of this variable causes the binary log to be rotated; checksums are always written to an entire binary log file, and never to only part of one.

Setting this variable on the master to a value unrecognized by the slave causes the slave to set its own binlog_checksum value to NONE, and to stop replication with an error. (Bug #13553750, Bug #61096) If backward compatibility with older slaves is a concern, you may want to set the value explicitly to NONE.

binlog_direct_non_transactional_updates

Due to concurrency issues, a slave can become inconsistent when a transaction contains updates to both transactional and nontransactional tables. MySQL tries to preserve causality among these statements by writing nontransactional statements to the transaction cache, which is flushed upon commit. However, problems arise when modifications done to nontransactional tables on behalf of a transaction become immediately visible to other connections because these changes may not be written immediately into the binary log.

The binlog_direct_non_transactional_updates variable offers one possible workaround to this issue. By default, this variable is disabled. Enabling binlog_direct_non_transactional_updates causes updates to nontransactional tables to be written directly to the binary log, rather than to the transaction cache.

binlog_direct_non_transactional_updates works only for statements that are replicated using the statement-based binary logging format; that is, it works only when the value of binlog_format is STATEMENT, or when binlog_format is MIXED and a given statement is being replicated using the statement-based format. This variable has no effect when the binary log format is ROW, or when binlog_format is set to MIXED and a given statement is replicated using the row-based format.

In MySQL 5.7, this variable has no effect when the binary log format is ROW or MIXED. (Bug #51291)

binlog_format

This variable sets the binary logging format, and can be any one of STATEMENT, ROW, or MIXED. See Section 16.1.2, "Replication Formats". binlog_format is set by the --binlog-format option at startup, or by the binlog_format variable at runtime.

In MySQL 5.7, the default format is STATEMENT.

You must have the SUPER privilege to set either the global or session binlog_format value.

The rules governing when changes to this variable take effect and how long the effect lasts are the same as for other MySQL server system variables. See Section 13.7.4, "SET Syntax", for more information.

When MIXED is specified, statement-based replication is used, except for cases where only row-based replication is guaranteed to lead to proper results. For example, this happens when statements contain user-defined functions (UDF) or the UUID() function. An exception to this rule is that MIXED always uses statement-based replication for stored functions and triggers.

There are exceptions when you cannot switch the replication format at runtime:

Trying to switch the format in those cases results in an error.

The binary log format affects the behavior of the following server options:

These effects are discussed in detail in the descriptions of the individual options.

binlog_max_flush_queue_time

How long in microseconds to keep reading transactions from the flush queue before proceeding with the group commit (and syncing the log to disk, if sync_binlog is greater than 0). If the value is 0 (the default), there is no timeout and the server keeps reading new transactions until the queue is empty.

Normally, binlog_max_flush_queue_time can remain set to 0. If the server processes a large number of connections (for example, 100 or more) and many short transactions with low-latency requirements, it may be useful to set the value larger than 0 to force more frequent flushes to disk.

binlog_order_commits

If this variable is enabled (the default), transactions are committed in the same order they are written to the binary log. If disabled, transactions may be committed in parallel. In some cases, disabling this variable might produce a performance increment.

binlog_row_image

In MySQL row-based replication, each row change event contains two images, a "before" image whose columns are matched against when searching for the row to be updated, and an "after" image containing the changes. Normally, MySQL logs full rows (that is, all columns) for both the before and after images. However, it is not strictly necessary to include every column in both images, and we can often save disk, memory, and network usage by logging only those columns which are actually required.

For the before image, it is necessary only that the minimum set of columns required to uniquely identify rows is logged. If the table containing the row has a primary key, then only the primary key column or columns are written to the binary log. Otherwise, if the table has a unique key all of whose columns are NOT NULL, then only the columns in the unique key need be logged. (If the table has neither a primary key nor a unique key without any NULL columns, then all columns must be used in the before image, and logged.) In the after image, it is necessary to log only the columns which have actually changed.

You can cause the server to log full or minimal rows using the binlog_row_image system variable. This variable actually takes one of three possible values, as shown in the following list:

The default value is full.

In MySQL 5.5 and earlier, full row images are always used for both before images and after images. If you need to replicate from a newer master to a slave running MySQL 5.5 or earlier, the master should always use this value.

When using minimal or noblob, deletes and updates are guaranteed to work correctly for a given table if and only if the following conditions are true for both the source and destination tables:

(In other words, the tables must be identical with the possible exception of indexes that are not part of the tables' primary keys.)

If these conditions are not met, it is possible that the primary key column values in the destination table may prove insufficient to provide a unique match for a delete or update. In this event, no warning or error is issued; the master and slave silently diverge, thus breaking consistency.

Setting this variable has no effect when the binary logging format is STATEMENT. When binlog_format is MIXED, the setting for binlog_row_image is applied to changes that are logged using row-based format, but this setting no effect on changes logged as statements.

Setting binlog_row_image on either the global or session level does not cause an implicit commit; this means that this variable can be changed while a transaction is in progress without affecting the transaction.

binlog_rows_query_log_events

The binlog_rows_query_log_events system variable affects row-based logging only. When enabled, it causes the MySQL Server to write informational log events such as row query log events into its binary log. This information can be used for debugging and related purposes; such as obtaining the original query issued on the master when it cannot be reconstructed from the row updates.

These events are normally ignored by MySQL programs reading the binary log and so cause no issues when replicating or restoring from backup.

binlog_stmt_cache_size

This variable determines the size of the cache for the binary log to hold nontransactional statements issued during a transaction. Separate binary log transaction and statement caches are allocated for each client if the server supports any transactional storage engines and if the server has the binary log enabled (--log-bin option). If you often use large nontransactional statements during transactions, you can increase this cache size to get better performance. The Binlog_stmt_cache_use and Binlog_stmt_cache_disk_use status variables can be useful for tuning the size of this variable. See Section 5.2.4, "The Binary Log".

The binlog_cache_size system variable sets the size for the transaction cache.

log_bin_basename

Holds the name and complete path to the binary log file. Unlike the log_bin system variable, log_bin_basename reflects the name set with the --log-bin server option.

log_bin_use_v1_row_events

Shows whether Version 2 binary logging is in use. A value of 1 shows that the server is writing the binary log using Version 1 logging events (the only version of binary log events used in previous releases), and thus producing a binary log that can be read by older slaves. 0 indicates that Version 2 binary log events are in use.

This variable is read-only. To switch between Version 1 and Version 2 binary event binary logging, it is necessary to restart mysqld with the --log-bin-use-v1-row-events option.

master_verify_checksum

Enabling this variable causes the master to examine checksums when reading from the binary log. master_verify_checksum is disabled by default; in this case, the master uses the event length from the binary log to verify events, so that only complete events are read from the binary log.

max_binlog_cache_size

If a transaction requires more than this many bytes of memory, the server generates a Multi-statement transaction required more than 'max_binlog_cache_size' bytes of storage error. The minimum value is 4096. The minimum value is 4096. The maximum possible value is 16EB (exabytes). The maximum recommended value is 4GB; this is due to the fact that MySQL currently cannot work with binary log positions greater than 4GB.

max_binlog_cache_size sets the size for the transaction cache only; the upper limit for the statement cache is governed by the max_binlog_stmt_cache_size system variable.

In MySQL 5.7, the visibility to sessions of max_binlog_cache_size matches that of the binlog_cache_size system variable; in other words, changing its value effects only new sessions that are started after the value is changed.

max_binlog_size

If a write to the binary log causes the current log file size to exceed the value of this variable, the server rotates the binary logs (closes the current file and opens the next one). The minimum value is 4096 bytes. The maximum and default value is 1GB.

A transaction is written in one chunk to the binary log, so it is never split between several binary logs. Therefore, if you have big transactions, you might see binary log files larger than max_binlog_size.

If max_relay_log_size is 0, the value of max_binlog_size applies to relay logs as well.

max_binlog_stmt_cache_size

If nontransactional statements within a transaction require more than this many bytes of memory, the server generates an error. The minimum value is 4096. The maximum and default values are 4GB on 32-bit platforms and 16EB (exabytes) on 64-bit platforms.

max_binlog_stmt_cache_size sets the size for the statement cache only; the upper limit for the transaction cache is governed exclusively by the max_binlog_cache_size system variable.

sync_binlog

If the value of this variable is greater than 0, the MySQL server synchronizes its binary log to disk (using fdatasync()) after sync_binlog commit groups are written to the binary log. The default value of sync_binlog is 0, which does no synchronizing to disk—in this case, the server relies on the operating system to flush the binary log's contents from time to time as for any other file. A value of 1 is the safest choice because in the event of a crash you lose at most one commit group from the binary log. However, it is also the slowest choice (unless the disk has a battery-backed cache, which makes synchronization very fast).