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https://dev.mysql.com/doc/refman/8.0/en/group-by-optimization.html
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/8.0/en/innodb-buffer-pool.html
The buffer pool is an area in main memory where InnoDB caches table and index data as it is accessed. A table scan, performed for a mysqldump operation or a SELECT statement with no WHERE clause, for example, can bring a large amount of data into ...The buffer pool permits frequently used data to be accessed directly from memory, which speeds up ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-change-buffer.html
On disk, the change buffer is part of the system tablespace, where index changes are buffered when the database server is shut down. Configuring Change Buffering When INSERT, UPDATE, and DELETE operations are performed on a table, the values of ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-memcached-multiple-get-range-query.html
The example uses the test.city table described in Creating a New Table and Column Mapping. For example, the table switch in this example is valid: get @@aaa.AA BB VALUE @@aaa.AA 8 12 HELLO, HELLO VALUE BB 10 16 GOODBYE, GOODBYE END Attempting to ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-memcached-replication.html
source $> mysqldump --all-databases --lock-all-tables > dbdump.db replica $> mysql < dbdump.db On the source server, issue SHOW MASTER STATUS to obtain the source binary log coordinates. The example uses the demo_test table, which was created by the ... Because the daemon_memcached plugin supports the MySQL binary log, source server through the memcached interface can be replicated for backup, balancing intensive read workloads, and high ...
https://dev.mysql.com/doc/refman/8.0/en/json.html
A maximum of 3 JSON columns per NDB table is supported. A direct assignment of the column value (for example, UPDATE mytable SET jcol = '{"a": 10, "b": 25}') cannot be performed as a partial update. The input column and the target column must be the ...The JSON data type provides these advantages over storing JSON-format strings in a string column: Automatic validation of JSON documents stored in JSON ...
https://dev.mysql.com/doc/refman/8.0/en/myisam-ftdump.html
It reads the MyISAM index file directly, so it must be run on the server host where the table is located. Before using myisam_ftdump, be sure to issue a FLUSH TABLES statement first if the server is running. Invoke myisam_ftdump like this: ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-limitations-database-objects.html
Some database objects such as tables and indexes have different limitations when using the NDBCLUSTER storage engine: Number of database objects. The maximum number of all NDB database objects in a single NDB Cluster—including databases, tables, ...In NDB 8.0, the maximum permitted size of any one row is 30000 bytes (increased from 14000 bytes in previous ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-log-events.html
Table 25.61 Events relating to NDB Cluster schema operations Event Priority Severity Level Description CreateSchemaObject 8 INFO Schema objected created AlterSchemaObject 8 INFO Schema object updated DropSchemaObject 8 INFO Schema object dropped ...
https://dev.mysql.com/doc/refman/8.0/en/nested-loop-joins.html
MySQL executes joins between tables using a nested-loop algorithm or variations on it. Nested-Loop Join Algorithm Block Nested-Loop Join Algorithm Nested-Loop Join Algorithm A simple nested-loop join (NLJ) algorithm reads rows from the first table ...For example, if 10 rows are read into a buffer and the buffer is passed to the next inner loop, each row read in the inner loop can be compared against all 10 rows in the ...