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https://dev.mysql.com/doc/refman/5.7/en/optimizing-innodb-storage-layout.html
In InnoDB, having a long PRIMARY KEY (either a single column with a lengthy value, or several columns that form a long composite value) wastes a lot of disk space. The primary key value for a row is duplicated in all the secondary index records that ... Once your data reaches a stable size, or a growing table has increased by tens or some hundreds of megabytes, consider using the OPTIMIZE TABLE statement to reorganize the table and compact any wasted ...
https://dev.mysql.com/doc/refman/5.7/en/optimizing-myisam-bulk-data-loading.html
Use myisamchk --keys-used=0 -rq /path/to/db/tbl_name to remove all use of indexes for the table. To increase performance for MyISAM tables, for both LOAD DATA and INSERT, enlarge the key cache by increasing the key_buffer_size system variable.
https://dev.mysql.com/doc/refman/5.7/en/partitioning-pruning.html
An INSERT statement also accesses only one partition per inserted row; this is true even for a table that is partitioned by HASH or KEY although this is not currently shown in the output of EXPLAIN. For tables that are partitioned by HASH or ...The ...
https://dev.mysql.com/doc/refman/5.7/en/program-variables.html
Both set the size of the server's key buffer to 512MB: [mysqld] key_buffer_size=512M [mysqld] key-buffer-size=512M In older versions of MySQL, program options could be specified in full or as any unambiguous prefix. Some implications of this change: ... Many MySQL programs have internal variables that can be set at runtime using the SET ...
https://dev.mysql.com/doc/refman/5.7/en/row-constructor-optimization.html
Consider the following table, which has a primary key on (c1, c2, c3): CREATE TABLE t1 ( c1 INT, c2 INT, c3 INT, c4 CHAR(100), PRIMARY KEY(c1,c2,c3) ); In this query, the WHERE clause uses all columns in the index. However, the row constructor ...
https://dev.mysql.com/doc/refman/5.7/en/storage-requirements.html
InnoDB Table Storage Requirements NDB Table Storage Requirements Numeric Type Storage Requirements Date and Time Type Storage Requirements String Type Storage Requirements Spatial Type Storage Requirements JSON Storage Requirements The storage ...
https://dev.mysql.com/doc/refman/5.7/en/subquery-optimization-with-exists.html
WHERE subquery_where AND (outer_expr=inner_expr OR inner_expr IS NULL)) The need to evaluate the extra IS NULL condition is why MySQL has the ref_or_null access method: mysql> EXPLAIN SELECT outer_expr IN (SELECT t2.maybe_null_key FROM t2, t3 WHERE ... Certain optimizations are applicable to comparisons that use the IN (or =ANY) operator to test subquery ...
https://dev.mysql.com/doc/refman/5.7/en/charset-collation-names.html
UCA-based collations without a version number in the name use the version-4.0.0 UCA weight keys. For example: utf8_unicode_520_ci is based on UCA 5.2.0 weight keys (http://www.unicode.org/Public/UCA/5.2.0/allkeys.txt). utf8_unicode_ci (with no ...
https://dev.mysql.com/doc/refman/5.7/en/charset-gb18030.html
Sorting of non-Chinese characters is based on the order of the original sort key. In MySQL, the gb18030 character set corresponds to the “Chinese National Standard GB 18030-2005: Information technology — Chinese coded character set”, which is ...
https://dev.mysql.com/doc/refman/5.7/en/charset-unicode-conversion.html
For example, the differences in maximum index key length make it risky to use utf8mb3 on the source and utf8mb4 on the replica. This section describes issues that you may face when converting character data between the utf8mb3 and utf8mb4 character ...