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https://dev.mysql.com/doc/refman/8.0/en/replication-snapshot-method.html
This can be more efficient than using mysqldump and importing the file on each replica, because it skips the overhead of updating indexes as the INSERT statements are replayed. Note By default, if GTIDs are in use on the source (gtid_mode=ON), ...
https://dev.mysql.com/doc/refman/8.0/en/replication-solutions-performance.html
Figure 19.3 Using an Additional Replication Source to Improve Performance For this to work, you must configure the MySQL instances as follows: Source 1 is the primary source where all changes and updates are written to the database. Source 2 has the ... As the number of replicas connecting to a source increases, the load, although minimal, also increases, as each replica uses a client connection to the ...
https://dev.mysql.com/doc/refman/8.0/en/replication-solutions-scaleout.html
Because replication works from the distribution of one source to one or more replicas, using replication for scale-out works best in an environment where you have a high number of reads and low number of writes/updates. Updates only occur during ...
https://dev.mysql.com/doc/refman/8.0/en/replication-threads.html
When a START REPLICA statement is issued on a replica server, the replica creates an I/O (receiver) thread, which connects to the source and asks it to send the updates recorded in its binary logs. The replication receiver thread reads the updates ... MySQL replication capabilities are implemented using the following types of threads: Binary log dump ...
https://dev.mysql.com/doc/refman/8.0/en/select-into.html
Example: SELECT * FROM t1 INTO @myvar FOR UPDATE; At the end of the SELECT. Example: SELECT * FROM t1 FOR UPDATE INTO @myvar; The INTO position at the end of the statement is supported as of MySQL 8.0.20, and is the preferred position. INTO form of ...
https://dev.mysql.com/doc/refman/8.0/en/serialized-dictionary-information.html
SDI data is updated by DDL operations on a table or CHECK TABLE FOR UPGRADE. SDI data is not updated when the MySQL server is upgraded to a new release or version. In addition to storing metadata about database objects in the data dictionary, MySQL ...
https://dev.mysql.com/doc/refman/8.0/en/show-columns.html
on update CURRENT_TIMESTAMP for TIMESTAMP or DATETIME columns that have the ON UPDATE CURRENT_TIMESTAMP attribute. SHOW [EXTENDED] [FULL] {COLUMNS | FIELDS} {FROM | IN} tbl_name [{FROM | IN} db_name] [LIKE 'pattern' | WHERE expr] SHOW COLUMNS ...
https://dev.mysql.com/doc/refman/8.0/en/sql-prepared-statements.html
Typically, database applications process large volumes of almost-identical statements, with only changes to literal or variable values in clauses such as WHERE for queries and deletes, SET for updates, and VALUES for inserts. Using prepared ...
https://dev.mysql.com/doc/refman/8.0/en/subquery-errors.html
Incorrect number of rows from subquery: ERROR 1242 (ER_SUBSELECT_NO_1_ROW) SQLSTATE = 21000 Message = "Subquery returns more than 1 row" This error occurs for statements where the subquery must return at most one row but returns multiple rows.
https://dev.mysql.com/doc/refman/8.0/en/subquery-optimization.html
Note A limitation on UPDATE and DELETE statements that use a subquery to modify a single table is that the optimizer does not use semijoin or materialization subquery optimizations. As a workaround, try rewriting them as multiple-table UPDATE and ...