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https://dev.mysql.com/doc/refman/8.4/en/index-btree-hash.html
For example, the following SELECT statements use indexes: SELECT * FROM tbl_name WHERE key_col LIKE 'Patrick%'; SELECT * FROM tbl_name WHERE key_col LIKE 'Pat%_ck%'; In the first statement, only rows with 'Patrick' <= key_col < 'Patricl' are ...
https://dev.mysql.com/doc/refman/8.4/en/index-statistics.html
Table statistics are based on value groups, where a value group is a set of rows with the same key prefix value. This affects ref accesses for comparisons of the form tbl_name.key = expr: MySQL does not access the table if the current value of expr ... Storage engines collect statistics about tables for use by the ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-fields-table.html
The INNODB_FIELDS table provides metadata about the key columns (fields) of InnoDB indexes. The INNODB_FIELDS table has these columns: INDEX_ID An identifier for the index associated with this key field; the same value as INNODB_INDEXES.INDEX_ID.
https://dev.mysql.com/doc/refman/8.4/en/information-schema-introduction.html
Information about generated invisible primary keys is visible by default in all INFORMATION_SCHEMA tables describing table columns, keys, or both, such as the COLUMNS and STATISTICS tables. INFORMATION_SCHEMA provides access to database metadata, ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-optimization.html
For ANALYZE TABLE operations that update the key distribution, failure may occur even if the operation updates the table itself (for example, if it is a MyISAM table). row *************************** id: 1 select_type: SIMPLE table: cs partitions: ... Applications that monitor databases may make frequent use of INFORMATION_SCHEMA ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-user-attributes-table.html
A comment is shown as a key-value pair having comment as the key. The USER_ATTRIBUTES table provides information about user comments and user attributes. The USER_ATTRIBUTES table has these columns: USER The user name portion of the account to ...
https://dev.mysql.com/doc/refman/8.4/en/innodb-create-table-external.html
CREATE TABLE t1 (c1 INT PRIMARY KEY) DATA DIRECTORY = '/external/directory'; The DATA DIRECTORY clause is supported for tables created in file-per-table tablespaces. mysql> CREATE TABLE t2 (c1 INT PRIMARY KEY) TABLESPACE = innodb_file_per_table DATA ... There are different reasons for creating InnoDB tables externally; that is, creating tables outside of the data ...
https://dev.mysql.com/doc/refman/8.4/en/load-index.html
tbl_index_list: tbl_name [PARTITION (partition_list)] [{INDEX|KEY} (index_name[, index_name] ...)] [IGNORE LEAVES] partition_list: { partition_name[, partition_name] ... | ALL } The LOAD INDEX INTO CACHE statement preloads a table index into the key ...LOAD INDEX INTO CACHE applies only to MyISAM tables, including partitioned MyISAM ...
https://dev.mysql.com/doc/refman/8.4/en/monitor-alter-table-performance-schema.html
In order of occurrence, ALTER TABLE stage events include: stage/innodb/alter table (read PK and internal sort): This stage is active when ALTER TABLE is in the reading-primary-key phase. It starts with WORK_COMPLETED=0 and WORK_ESTIMATED set to the ... You can monitor ALTER TABLE progress for InnoDB tables using Performance ...
https://dev.mysql.com/doc/refman/8.4/en/myisam-check.html
It calculates a checksum for all key values in the rows and verifies that the checksum matches the checksum for the keys in the index tree. It does a check-read of every key for each row to verify that they indeed point to the correct row. To check ...