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https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-options-variables.html
(It is neither necessary nor desirable to use this option together with --initialize.) --ndb-allow-copying-alter-table=[ON|OFF] Command-Line Format --ndb-allow-copying-alter-table[={OFF|ON}] System Variable ndb_allow_copying_alter_table Scope ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-online-ddl-operations.html
The CREATE INDEX statement only finishes after all transactions that are accessing the table are completed, so that the initial state of the index reflects the most recent contents of the table. A newly created secondary index contains only the ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-columns-table.html
A UNIQUE index may display as MUL if several columns form a composite UNIQUE index; although the combination of the columns is unique, each column can still hold multiple occurrences of a given value. COLUMN_KEY Whether the column is indexed: If ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-persistent-stats.html
If innodb_stats_auto_recalc is disabled, you can ensure the accuracy of optimizer statistics by executing the ANALYZE TABLE statement after making substantial changes to indexed columns. When an index is added to an existing table, or when a column ... The persistent optimizer statistics feature improves plan stability by storing statistics to disk and making them persistent across server restarts so that the optimizer is more likely to make consistent choices each time for a given ...
https://dev.mysql.com/doc/refman/8.4/en/optimizing-innodb-storage-layout.html
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 space. This is a straightforward technique that ...The reorganized tables require less disk I/O to perform full table ...
https://dev.mysql.com/doc/refman/8.4/en/group-by-optimization.html
In some cases, MySQL is able to do much better than that and avoid creation of temporary tables by using index access. The most important preconditions for using indexes for GROUP BY are that all GROUP BY columns reference attributes from the same ... The most general way to satisfy a GROUP BY clause is to scan the whole table and create a new temporary table where all rows from each group are consecutive, and then use this temporary table to discover groups and apply aggregate functions (if ...
https://dev.mysql.com/doc/refman/8.4/en/order-by-optimization.html
It refers to t1.a, as does the reference to a in the ORDER BY, so the index on t1.a can be used: SELECT a FROM t1 ORDER BY a; In this statement, the name of the column in the select list is also a, but it is the alias name. This section describes ...An ORDER BY with and without LIMIT may return rows in different orders, as discussed in Section 10.2.1.19, “LIMIT Query ...
https://dev.mysql.com/doc/refman/8.4/en/ansi-diff-foreign-keys.html
In an SQL statement that inserts, deletes, or updates many rows, foreign key constraints (like unique constraints) are checked row-by-row. That is, constraints are only checked after the entire SQL statement has been processed. The MATCH clause in ...For example, if you define a RESTRICT type constraint, and there is a child row with several parent rows, InnoDB does not permit the deletion of any of the parent ...
https://dev.mysql.com/doc/heatwave/en/mys-hw-lakehouse-table-syntax-json.html
External tables use table-level and column-level ENGINE_ATTRIBUTE options of the CREATE TABLE statement to specify the parameters needed to process data stored externally in Object Storage. CREATE EXTERNAL TABLE table_name (col_name data_type ...
https://dev.mysql.com/doc/refman/8.4/en/partitioning-list.html
ADD PARTITION statement to restore the table's original partitioning scheme.) As with RANGE partitioning, it is possible to combine LIST partitioning with partitioning by hash or key to produce a composite partitioning (subpartitioning). For more ...