Search Results
https://dev.mysql.com/doc/refman/8.4/en/innodb-physical-structure.html
InnoDB performs a bulk load when creating or rebuilding B-tree indexes. This method of index creation is known as a sorted index build. With the exception of spatial indexes, InnoDB indexes are B-tree data structures. Spatial indexes use R-trees, ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-recovery.html
In some cases of database corruption, it is enough to dump, drop, and re-create one or a few corrupt tables. To achieve point-in-time recovery after restoring a backup, you can apply changes from the binary log that occurred after the backup was ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-table-compression.html
Table compression is enabled using the ROW_FORMAT=COMPRESSED attribute with CREATE TABLE or ALTER TABLE. This section describes InnoDB table compression, which is supported with InnoDB tables that reside in file_per_table tablespaces or general ...
https://dev.mysql.com/doc/refman/8.4/en/key-space.html
In MyISAM tables, you can also prefix compress numbers by specifying the PACK_KEYS=1 table option when you create the table. You can roughly calculate the size for the index file as (key_length+4)/0.67, summed over all keys. This is for the worst ...
https://dev.mysql.com/doc/refman/8.4/en/known-issues.html
Creation of a table of type MERGE does not check whether the underlying tables are compatible types. This section lists known issues in recent versions of MySQL. For information about platform-specific issues, see the installation and debugging ...
https://dev.mysql.com/doc/refman/8.4/en/loop.html
Example: CREATE PROCEDURE doiterate(p1 INT) BEGIN label1: LOOP SET p1 = p1 + 1; IF p1 < 10 THEN ITERATE label1; END IF; LEAVE label1; END LOOP label1; SET @x = p1; END; . [begin_label:] LOOP statement_list END LOOP [end_label] LOOP implements a ...
https://dev.mysql.com/doc/refman/8.4/en/mathematical-functions.html
ABS(X) Returns the absolute value of X, or NULL if X is NULL. An implication of this is that ABS(-9223372036854775808) produces an error because the result cannot be stored in a signed BIGINT value. mysql> SELECT ABS(2); -> 2 mysql> SELECT ABS(-32); ...
https://dev.mysql.com/doc/refman/8.4/en/miscellaneous-optimization-tips.html
If possible, classify reports as “live” or as “statistical”, where data needed for statistical reports is created only from summary tables that are generated periodically from the live data. This section lists a number of miscellaneous tips ...
https://dev.mysql.com/doc/refman/8.4/en/monitor-innodb-mutex-waits-performance-schema.html
A mutex is a synchronization mechanism used in the code to enforce that only one thread at a given time can have access to a common resource. When two or more threads executing in the server need to access the same resource, the threads compete ...
https://dev.mysql.com/doc/refman/8.4/en/mrr-optimization.html
The MRR optimization is not supported with secondary indexes created on virtual generated columns. Reading rows using a range scan on a secondary index can result in many random disk accesses to the base table when the table is large and not stored ...