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https://dev.mysql.com/doc/refman/5.7/en/multiple-column-indexes.html
MySQL can create composite indexes (that is, indexes on multiple columns). For certain data types, you can index a prefix of the column (see Section 8.3.4, “Column Indexes”). MySQL can use multiple-column indexes for queries that test all the ...
https://dev.mysql.com/doc/refman/5.7/en/where-optimization.html
At one time, a scan was used based on whether the best index spanned more than 30% of the table, but a fixed percentage no longer determines the choice between using an index or a scan. This section discusses optimizations that can be made for ...
https://dev.mysql.com/doc/refman/5.7/en/replication-howto-additionalslaves.html
Alternatively, if you have already tried to start the new replica after following the remaining steps in this section and have encountered errors like those described previously, then perform the following steps: If you have not already done so, ...
https://dev.mysql.com/doc/refman/5.7/en/charset-general.html
In real life, most character sets have many characters: not just A and B but whole alphabets, sometimes multiple alphabets or eastern writing systems with thousands of characters, along with many special symbols and punctuation marks. A character ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndbd.html
--connect-delay=# Command-Line Format --connect-delay=# Deprecated Yes (removed in 5.7.36-ndb-7.6.21) Type Numeric Default Value 5 Minimum Value 0 Maximum Value 3600 Determines the time to wait between attempts to contact a management server when ...
https://dev.mysql.com/doc/refman/5.7/en/session-state-tracking.html
A client can enable these trackers to receive notification of changes to its session state. Uses for Session State Trackers Available Session State Trackers C API Session State Tracker Support Test Suite Session State Tracker Support Uses for ...
https://dev.mysql.com/doc/refman/5.7/en/sys-statements-with-sorting.html
total_latency The total wait time of timed occurrences of the statement. last_seen The time at which the statement was most recently seen. The statements_with_sorting and x$statements_with_sorting views have these columns: query The normalized ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-performance-use_sys_malloc.html
When InnoDB was developed, the memory allocators supplied with operating systems and run-time libraries were often lacking in performance and scalability. At that time, there were no memory allocator libraries tuned for multi-core CPUs. Therefore, ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-innodb-cmp-per-index-table.html
COMPRESS_TIME The total time in seconds used for compressing data in this index. UNCOMPRESS_TIME The total time in seconds used for uncompressing data in this index. For a compressed InnoDB table, both the table data and all the secondary indexes ...
https://dev.mysql.com/doc/refman/5.7/en/replication-solutions-performance.html
This prevents “dumb” replicas from also logging events they have executed into their own binary log. As the number of replicas connecting to a source increases, the load, although minimal, also increases, as each replica uses a client ...