Author: Abhishek Yadav
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Serialized Dictionary Information (SDI)
In addition to storing metadata about database objects in the data dictionary, MySQL stores it in serialized form. This data is referred to as serialized dictionary information (SDI). InnoDB stores SDI data within its tablespace files. NDBCLUSTER stores SDI data in the NDB dictionary. Other storage engines store SDI data in .sdi files that are created for a given table in the table’s…
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Removal of File-based Metadata Storage
In previous MySQL releases, dictionary data was partially stored in metadata files. Issues with file-based metadata storage included expensive file scans, susceptibility to file system-related bugs, complex code for handling of replication and crash recovery failure states, and a lack of extensibility that made it difficult to add metadata for new features and relational objects.…
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Transactional Storage of Dictionary Data
The data dictionary schema stores dictionary data in transactional (InnoDB) tables. Data dictionary tables are located in the mysql database together with non-data dictionary system tables. Data dictionary tables are created in a single InnoDB tablespace named mysql.ibd, which resides in the MySQL data directory. The mysql.ibd tablespace file must reside in the MySQL data directory and its name cannot be modified…
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InnoDB Engine
InnoDB is a general-purpose storage engine that balances high reliability and high performance. In MySQL 8.0, InnoDB is the default MySQL storage engine. Unless you have configured a different default storage engine, issuing a CREATE TABLE statement without an ENGINE= clause creates an InnoDB table. Key Advantages of InnoDB
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InnoDB Multi-Versioning
InnoDB is a multi-versioned storage engine: it keeps information about old versions of changed rows, to support transactional features such as concurrency and rollback. This information is stored in the tablespace in a data structure called a rollback segment (after an analogous data structure in Oracle). InnoDB uses the information in the rollback segment to perform the undo operations needed in a…
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MySQL Physical (Raw) Vs Logical Backups
Physical backups consist of raw copies of the directories and files that store database contents. This type of backup is suitable for large, important databases that need to be recovered quickly when problems occur. Logical backups save information represented as logical database structure (CREATE DATABASE, CREATE TABLE statements) and content (INSERT statements or delimited-text files). This type of…
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MySQL Full Vs Incremental Backups
A full backup includes all data managed by a MySQL server at a given point in time. An incremental backup consists of the changes made to the data during a given time span (from one point in time to another). MySQL has different ways to perform full backups, such as those described earlier in this…
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MySQL Full Versus Point-in-Time (Incremental) Recovery
A full recovery restores all data from a full backup. This restores the server instance to the state that it had when the backup was made. If that state is not sufficiently current, a full recovery can be followed by recovery of incremental backups made since the full backup, to bring the server to a…
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SHOW PROCESSLIST Statement
The MySQL process list indicates the operations currently being performed by the set of threads executing within the server. The SHOW PROCESSLIST statement is one source of process information. For a comparison of this statement with other sources, see Sources of Process Information. If you have the PROCESS privilege, you can see all threads, even those belonging to other users.…
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Important PS (Power shell) Scripts
$a = get-eventlog -logname system -message *SQL* -newest 1 $a | select-object -property * ————————————————————————————————————- EventID : 7036 MachineName : ABCD Data : {83, 0, 81, 0…} Index : 4281381 Category …
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MySQL Uptime
MySQL Uptime SELECT VARIABLE_VALUE AS Uptime_seconds, NOW() AS “Now”, NOW() – INTERVAL VARIABLE_VALUE SECOND AS “Up since”, DATEDIFF(NOW(), NOW() – INTERVAL VARIABLE_VALUE SECOND) AS “Uptime_days” FROM performance_schema.session_status WHERE VARIABLE_NAME = ‘Uptime’; Output Example: +—————-+———————+—————————-+————-+ | Uptime_seconds | Now | Up since …
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