by Jeremy Cole
Note: This document is a work in progress. If you have some ideas, comments, or suggestions, please feel free to contact me.
Background
MySQL’s configuration files currently use a nearly flat namespace: the namespace is only divided between programs, such as the group names [mysqld], [mysql], and [mysqldump].
The problem
Given that MySQL has many storage engines now, and that it’s getting more and more features added every day, the flat namespace has been quickly outgrown. It’s very difficult to remember all of the different configuration options, what they relate to, and when and where they are allocated.
For example: What’s the difference between sort_buffer_size and myisam_sort_buffer_size? What storage engines use read_buffer_size?
Many variables are prefixed with some kind of feature or storage engine name, but it’s inconsistent and often overly verbose.
My proposed solution
I propose to rename all of MySQL’s configuration variables into a multi-level hierarchical namespace, for example:
key_buffer_size —> engine.myisam.key_cache.size
innodb_buffer_pool_size —> engine.innodb.buffer_pool.size
The old names can be supported for a long time, but new variables should only be added with the new namespace-format names. (Unless the variable is added to an older version of MySQL.)
Complete (not yet, though!) list of proposed name changes
| Old Name | New Name |
| global.* | |
| basedir | global.basedir |
| datadir | global.datadir |
| pid_file | global.pid_file |
| global.net.* | |
| back_log | global.net.back_log |
| net_read_timeout | global.net.read_timeout |
| net_write_timeout | global.net.write_timeout |
| net_retry_count | global.net.retry_count |
| global.net.tcp.* | |
| port | global.net.tcp.port |
| global.net.unix.* | |
| socket | global.net.unix.socket |
| global.log.* | |
| log | global.log.general |
| log_bin | global.log.binlog |
| max_binlog_size | global.log.binlog.max_size |
| binlog_cache_size | global.log.binlog.cache_size |
| log_slave_updates | global.log.binlog.log_slave_updates |
| log_slow_queries | global.log.slow |
| long_query_time | global.log.slow.time_limit |
| global.query_cache.* | |
| query_cache_size | global.query_cache.size |
| query_cache_type | global.query_cache.type |
| query_cache_min_res_unit | global.query_cache.min_res_unit |
| query_cache_limit | global.query_cache.result_limit_size |
| query_alloc_block_size | global.query_cache.block_alloc_size |
| query_cache_wlock_invalidate | global.query_cache.wlock_invalidate |
| global.fulltext.* | |
| ft_boolean_syntax | global.fulltext.boolean_syntax |
| ft_max_word_len | global.fulltext.word_len.max |
| ft_min_word_len | global.fulltext.word_len.min |
| ft_query_expansion_limit | global.fulltext.query_expansion_limit |
| ft_stopword_file | global.fulltext.stopword_file |
| global.replication.* | |
| server_id | global.replication.server_id |
| slave_net_timeout | global.replication.slave.net_timeout |
| slave_transaction_retries | global.replication.slave.transaction_retries |
| global.auto_increment.* | |
| auto_increment_offset | global.auto_increment.offset |
| auto_increment_increment | global.auto_increment.increment |
| session.* | |
| sort_buffer_size | session.sort_buffer_size |
| wait_timeout | session.timeout.general |
| interactive_timeout | session.timeout.interactive |
| engine.myisam.* | |
| key_buffer_size | engine.myisam.key_cache.size |
| key_cache_age_threshold | engine.myisam.key_cache.age_threshold |
| key_cache_block_size | engine.myisam.key_cache.block_size |
| key_cache_division_limit | engine.myisam.key_cache.division_limit |
| myisam_data_pointer_size | engine.myisam.data_pointer_size |
| myisam_sort_buffer_size | engine.myisam.repair.sort_buffer_size |
| myisam_repair_threads | engine.myisam.repair.threads |
| myisam_stats_method | engine.myisam.stats_method |
| read_buffer_size | engine.myisam.read_buffer_size |
| read_rnd_buffer_size | engine.myisam.read_rnd_buffer_size |
| engine.innodb.* | |
| innodb_data_home_dir | engine.innodb.data.home_dir |
| innodb_data_file_path | engine.innodb.data.files |
| innodb_log_group_home_dir | engine.innodb.log.home_dir |
| innodb_log_files_in_group | engine.innodb.log.files_in_group |
| innodb_log_file_size | engine.innodb.log.file_size |
| innodb_log_archive | engine.innodb.log.archive |
| innodb_log_arch_dir | engine.innodb.log.archive_dir |
| innodb_log_buffer_size | engine.innodb.log.buffer_size |
| innodb_buffer_pool_size | engine.innodb.buffer_pool.size |
| innodb_buffer_pool_awe_mem_mb | engine.innodb.buffer_pool.awe_mem_mb |
| engine.heap.* | |
| engine.archive.* | |
| engine.ndb.* | |
Legacy support
In order to continue to support all of the old variable names, a new namespace would be created, called legacy.* and all of the old names for variables would be mapped into it. For the first major MySQL version that supports namespaces, any variable without a dot in it would be mapped to legacy.*, which would allow them to continue working. For the next major version, the legacy.* namespace could still be supported, but without the automatic mapping. In the future, the legacy.* namespace could be dropped completely.
