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MariaDB 10.1.1: Defragmenting unused space on InnoDB tablespace

Introduction When you e.g. delete rows, these rows are just marked as deleted not really physically deleted from indexes and free space introduced is not returned to operating system for later reuse. Purge thread will physically delete index keys and rows, but still free space introduced is not returned to operating system and this operation […]

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MariaDB 10.1.1: Monitoring progress and temporal memory usage of Online DDL in InnoDB

Introduction Online DDL is a new feature in MariaDB 10.0. Online DDL is processed through below 4 tasks in sequence. InnoDB::ha_prepare_inplace_alter_table(..) InnoDB::ha_inplace_alter_table(..) InnoDB::ha_commit_inplace_alter_table(..) mysql_rename_table(..) InnoDB storage engine allocates temporal memory buffer for transaction logging in phase 1 where row changes during this phase are logged. Size of this buffer is at start sort_buffer_size and it […]

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MariaDB 10.1.1: FLUSH and SHOW for plugins

One of the most popular plugin types both in MariaDB and MySQL is INFORMATION_SCHEMA plugin type. INFORMATION_SCHEMA plugins add new tables to the INFORMATION_SCHEMA. There are lots of INFORMATION_SCHEMA plugins, because they can be used to show just anything to the user and are very easy to write. MariaDB 10.1.1 comes with nine INFORMATION_SCHEMA plugin: […]

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MariaDB 10.1.1: Compound statements

Every now and then there is a need to execute certain SQL statements conditionally. Easy, if you do it from your PHP (or Java or whatever) application. But if all you have is pure SQL? There are two techniques that MariaDB and MySQL use in the mysql_fix_privilege_tables.sql script (applied by mysql_upgrade tool). Create a stored […]

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MariaDB 10.1.1: no more .frm’s for performance_schema tables

Yes! In MariaDB 10.1.1 tables in PERFORMANCE_SCHEMA do not use .frm files. These files are not created, not read — in fact, PERFORMANCE_SCHEMA tables never touch the disk at all. This became possible due to a lesser-known feature of MariaDB — new table discovery (“old table discovery” was implemented in MySQL for NDB Cluster in […]

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