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https://dev.mysql.com/doc/refman/5.7/en/set-variable.html
A SET statement that assigns variable values is not written to the binary log, so in replication scenarios it affects only the host on which you execute it. To affect all replication hosts, execute the statement on each host. User-Defined Variable ...variable: { user_var_name | param_name | local_var_name | {GLOBAL | @@GLOBAL.} system_var_name | [SESSION | ...
https://dev.mysql.com/doc/refman/5.7/en/create-table-secondary-indexes.html
A secondary index defined on a virtual column is sometimes referred to as a “virtual index”. If a secondary index is not defined on a virtual column, there are additional costs for reads, as virtual column values must be computed each time the ...A secondary index may be created on one or more virtual columns or on a combination of virtual columns and regular columns or stored generated ...If the index is a covering index (one that includes all the ...
https://dev.mysql.com/doc/refman/5.7/en/create-table.html
An error occurs if the table exists, if there is no default database, or if the database does not exist. IF NOT EXISTS Prevents an error from occurring if the table exists. Column Data Types and Attributes There is a hard limit of 4096 columns per ...| {FULLTEXT | SPATIAL} [INDEX | KEY] [index_name] (key_part,...) [index_option] ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-analyze-table-complexity.html
Using these parameters, an approximate formula for estimating ANALYZE TABLE complexity would be: The value of innodb_stats_persistent_sample_pages * number of indexed columns in a table * the number of partitions Typically, the greater the resulting ... ANALYZE TABLE complexity for InnoDB tables is dependent on: The number of pages sampled, as defined by ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-statement-summary-tables.html
For example, the SUM_LOCK_TIME and SUM_ERRORS columns in statement summary tables are the aggregates of the LOCK_TIME and ERRORS columns in events_statements_current table. The prepared_statements_instances table has these additional summary ...(The ... The Performance Schema maintains tables for collecting current and recent statement events, and aggregates that information in summary ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-multi-versioning.html
This removal operation is called a purge, and it is quite fast, usually taking the same order of time as the SQL statement that did the deletion. Multi-Versioning and Secondary Indexes InnoDB multiversion concurrency control (MVCC) treats secondary ...It keeps information about old versions of changed rows to support transactional features such as concurrency and ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-undo-logs.html
InnoDB supports a maximum of 128 rollback segments, 32 of which are allocated to the temporary tablespace. Note It is possible to encounter a concurrent transaction limit error before reaching the number of concurrent read-write transactions that ...
https://dev.mysql.com/doc/refman/5.7/en/select-optimization.html
Tuning these statements is a top priority, whether to achieve sub-second response times for dynamic web pages, or to chop hours off the time to generate huge overnight reports. With efficient use of the InnoDB buffer pool, MyISAM key cache, and the ...NDB Cluster supports a join pushdown optimization whereby a qualifying join is sent in its entirety to NDB Cluster data nodes, where it can be distributed among them and executed in ...
https://dev.mysql.com/doc/refman/5.7/en/partitioning-limitations-partitioning-keys-unique-keys.html
This section discusses the relationship of partitioning keys with primary keys and unique keys. The rule governing this relationship can be expressed as follows: All columns used in the partitioning expression for a partitioned table must be part ...
https://dev.mysql.com/doc/refman/5.7/en/using-system-variables.html
To restrict the maximum value to which a system variable can be set at runtime with the SET statement, specify this maximum by using an option of the form --maximum-var_name=value at server startup. For example, to prevent the value of ...The ...