# TokuDB introduction

!!! important

    Starting with [Percona Server for MySQL 8.0.28-19](../release-notes/Percona-Server-8.0.28-19.md), the TokuDB storage engine is no longer supported. We have removed the storage engine from the installation packages and disabled the storage engine in our binary builds.

    Starting with [Percona Server for MySQL 8.0.26-16](../release-notes/Percona-Server-8.0.26-16.md), the binary builds and packages include but disable the TokuDB storage engine plugins. The tokudb_enabled option and the tokudb_backup_enabled option control the state of the plugins and have a default setting of FALSE. The result of attempting to load the plugins are the plugins fail to initialize and print a deprecation message.

    We recommend [Migrating the data to the MyRocks storage engine](https://docs.percona.com/percona-server/latest/tokudb/removing_tokudb.html#migrate-myrocks). To enable the plugins to migrate to another storage engine, set the tokudb_enabled and tokudb_backup_enabled options to TRUE in your my.cnf file and restart your server instance. Then, you can load the plugins.

    The TokuDB storage engine was declared as deprecated in [Percona Server for MySQL 8.0](../release-notes/Percona-Server-8.0.13-3.md). For more information, see the Percona blog post: [Heads-Up: TokuDB Support Changes and Future Removal from Percona Server for MySQL 8.0](https://www.percona.com/blog/2021/05/21/tokudb-support-changes-and-future-removal-from-percona-server-for-mysql-8-0/).

*TokuDB* is a highly scalable, zero-maintenance downtime MySQL storage engine
that delivers indexing-based query acceleration, improved replication
performance, unparalleled compression, and live schema modification. The
*TokuDB* storage engine is a scalable, ACID and MVCC compliant storage engine
that provides indexing-based query improvements, offers online schema
modifications, and reduces replica lag for both hard disk drives and flash
memory. This storage engine is specifically designed for high performance on
write-intensive workloads which is achieved with Fractal Tree indexing.

*Percona Server for MySQL* is compatible with the separately available *TokuDB* storage
engine package. The *TokuDB* engine must be separately downloaded and then
enabled as a plug-in component. This package can be installed alongside with
standard *Percona Server for MySQL* releases and does not require any specially adapted
version of *Percona Server for MySQL*.

!!! warning

    Only the [Percona supplied](https://www.percona.com/downloads/Percona-Server-8.0/LATEST/) *TokuDB* engine should be used with *Percona Server for MySQL*. A *TokuDB* engine downloadedfrom other sources is not compatible. *TokuDB* file formats are not the same across MySQL variants. Migrating from one variant to any other variant requires a logical data dump and reload.

Additional features unique to *TokuDB* include:

* Up to 25x Data Compression

* Fast Inserts

* Eliminates Replica Lag with Read Free Replication

* Hot Schema Changes

* Hot Index Creation - *TokuDB* tables support insertions, deletions and queries
with no down time while indexes are being added to that table

* Hot column addition, deletion, expansion, and rename - *TokuDB* tables support
insertions, deletions and queries without down-time when an alter table adds,
deletes, expands, or renames columns

* On-line Backup

!!! note

    The *TokuDB* storage engine does not support the `nowait` and `skip locked` modifiers introduced in the *InnoDB* storage engine with *MySQL* 8.0.

For more information on installing and using *TokuDB* click on the following
links:

* [TokuDB Installation](tokudb_intro.md)

* [Using TokuDB](using_tokudb.md)

* [Getting Started with TokuDB](tokudb_quickstart.md)

* [TokuDB Variables](tokudb_variables.md)

* [Percona TokuBackup](toku_backup.md)

* [TokuDB Troubleshooting](tokudb_troubleshooting.md)

* [Frequently Asked Questions](tokudb_faq.md)

* [Migrating and Removing the TokuDB storage engine](removing_tokudb.md)


## Getting the Most from TokuDB

Compression

    *TokuDB* compresses all data on disk, including indexes. Compression
    lowers cost by reducing the amount of storage required and frees up disk
    space for additional indexes to achieve improved query performance. Depending
    on the compressibility of the data, we have seen compression ratios up to 25x
    for high compression. Compression can also lead to improved performance since
    less data needs to be read from and written to disk.

Fast Insertions and Deletions

    TokuDB’s Fractal Tree technology enables fast
    indexed insertions and deletions. Fractal Trees match B-trees in their
    indexing sweet spot (sequential data) and are up to two orders of magnitude
    faster for random data with high cardinality.

Eliminates Replica Lag

    *TokuDB* replication replicas can be configured to process
    the replication stream with virtually no read IO. Uniqueness checking is
    performed on the *TokuDB* source and can be skipped on all *TokuDB*
    replica. Also, row based replication ensures that all before and after row
    images are captured in the binary logs, so the *TokuDB* replicas can harness
    the power of Fractal Tree indexes and bypass traditional read-modify-write
    behavior. This “Read Free Replication” ensures that replication replicas do not
    fall behind the source and can be used for read scaling, backups, and
    disaster recovery, without sharding, expensive hardware, or limits on what
    can be replicated.

Hot Index Creation

    *TokuDB* allows the addition of indexes to an existing table
    while inserts and queries are being performed on that table. This means that
    *MySQL* can be run continuously with no blocking of queries or insertions
    while indexes are added and eliminates the down-time that index changes would
    otherwise require.

Hot Column Addition, Deletion, Expansion and Rename

    *TokuDB* allows the addition
    of new columns to an existing table, the deletion of existing columns from an
    existing table, the expansion of `char`, `varchar`, `varbinary`, and
    `integer` type columns in an existing table, and the renaming of an
    existing column while inserts and queries are being performed on that table.

Online (Hot) Backup

    The *TokuDB* can create backups of online database servers without downtime.

Fast Indexing

    In practice, slow indexing often leads users to choose a smaller
    number of sub-optimal indexes in order to keep up with incoming data
    rates. These sub-optimal indexes result in disproportionately slower queries,
    since the difference in speed between a query with an index and the same
    query when no index is available can be many orders of magnitude. Thus, fast
    indexing means fast queries.

Clustering Keys and Other Indexing Improvements

    *TokuDB* tables are clustered on
    the primary key. *TokuDB* also supports clustering secondary keys, providing
    better performance on a broader range of queries. A clustering key includes
    (or clusters) all of the columns in a table along with the key. As a result,
    one can efficiently retrieve any column when doing a range query on a
    clustering key. Also, with *TokuDB*, an auto-increment column can be used in
    any index and in any position within an index. Lastly, *TokuDB* indexes can
    include up to 32 columns.

Less Aging/Fragmentation

    *TokuDB* can run much longer, likely indefinitely,
    without the need to perform the customary practice of dump/reload or
    `OPTIMIZE TABLE` to restore database performance. The key is the
    fundamental difference with which the Fractal Tree stores data on
    disk. Since, by default, the Fractal Tree will store data in 4MB chunks
    (pre-compression), as compared to InnoDB’s 16KB, *TokuDB* has the ability to
    avoid “database disorder” up to 250x better than InnoDB.

Bulk Loader

    *TokuDB* uses a parallel loader to create tables and offline
    indexes. This parallel loader will use multiple cores for fast offline table
    and index creation.

Full-Featured Database

    *TokuDB* supports fully ACID-compliant transactions, MVCC
    (Multi-Version Concurrency Control), serialized isolation levels, row-level
    locking, and XA. *TokuDB* scales with high number of client connections, even
    for large tables.

Lock Diagnostics

    *TokuDB* provides users with the tools to diagnose locking and
    deadlock issues. For more information, see [Lock Visualization in TokuDB](tokudb_troubleshooting.md#lock-visualization-in-tokudb).

Progress Tracking

    Running `SHOW PROCESSLIST` when adding indexes provides
    status on how many rows have been processed. Running `SHOW PROCESSLIST`
    also shows progress on queries, as well as insertions, deletions and
    updates. This information is helpful for estimating how long operations will
    take to complete.

Fast Recovery

    *TokuDB* supports very fast recovery, typically less than a minute.