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https://dev.mysql.com/doc/refman/8.4/en/cost-model.html
The larger default values for these disk parameters compared to the default values for the corresponding memory parameters (memory_temptable_create_cost, memory_temptable_row_cost) reflects the greater cost of processing disk-based tables. DBAs can ... To generate execution plans, the optimizer uses a cost model that is based on estimates of the cost of various operations that occur during query ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-partitions-table.html
Each row in this table corresponds to an individual partition or subpartition of a partitioned table. SUBPARTITION_NAME If the PARTITIONS table row represents a subpartition, the name of subpartition; otherwise NULL. For partitioned InnoDB tables, ...The PARTITIONS table has these columns: TABLE_CATALOG The name of the catalog to which the table ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-autocommit-commit-rollback.html
$> mysql test mysql> CREATE TABLE customer (a INT, b CHAR (20), INDEX (a)); Query OK, 0 rows affected (0.00 sec) mysql> -- Do a transaction with autocommit turned on. mysql> START TRANSACTION; Query OK, 0 rows affected (0.00 sec) mysql> INSERT INTO ...If autocommit mode is enabled, each SQL statement forms a single transaction on its ...
https://dev.mysql.com/doc/refman/8.4/en/ldml-collation-example.html
To add a UCA collation for a Unicode character set without recompiling MySQL, use the following procedure. If you are unfamiliar with the LDML rules used to describe the collation's sort characteristics, see Section 12.14.4.2, “LDML Syntax ...
https://dev.mysql.com/doc/refman/8.4/en/partitioning-range.html
A table that is partitioned by range is partitioned in such a way that each partition contains rows for which the partitioning expression value lies within a given range. MAXVALUE represents an integer value that is always greater than the largest ...Ranges should be contiguous but not overlapping, and are defined using the VALUES LESS THAN ...
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-stage-summary-tables.html
row *************************** EVENT_NAME: stage/sql/checking permissions COUNT_STAR: 57 SUM_TIMER_WAIT: 26501888880 MIN_TIMER_WAIT: 7317456 AVG_TIMER_WAIT: 464945295 MAX_TIMER_WAIT: 12858936792 ... row *************************** EVENT_NAME: ...
https://dev.mysql.com/doc/refman/8.4/en/subqueries.html
All subquery forms and operations that the SQL standard requires are supported, as well as a few features that are MySQL-specific. Here is an example of a subquery: SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2); In this example, SELECT * ...
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-trace-statement-digest.html
| +-----------------------------------------------------------------+ 1 row in set (9.17 sec) +------------------------------------------+-----------+ | event_name | latency | +------------------------------------------+-----------+ | stage/sql/init ... Traces all Performance Schema instrumentation for a specific statement ...
https://dev.mysql.com/doc/refman/8.4/en/time-zone-support.html
The following query determines whether the table that contains time zone names has any rows: mysql> SELECT COUNT(*) FROM mysql.time_zone_name; +----------+ | COUNT(*) | +----------+ | 0 | +----------+ A count of zero indicates that the table is ...
https://dev.mysql.com/doc/mysql-cluster-manager/8.4/en/mcm-change-process.html
change process [--sequential-restart] old_proc_type[:proc-id]=new_proc_type cluster_name old_proc_type | new_proc_type: {ndbd|ndbmtd} This command is used to change the process type for a given MySQL NDB Cluster process or group of MySQL NDB ...