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{{Short description|Database engine}}

== MySQL Archive Storage Engine ==

{{ Infobox Software

| name = ArchiveStorage Engine

| logo =

| screenshot =

| caption =

| author = [[Brian Aker]]

| collapsible = yes

| developer =

| released = 2004

| latest release version =

| latest release date =

| latest preview version =

| latest preview date =

| operating system = [[Cross-platform]]

| platform = [[x86 architecture|x86]], [[x86-64]], [[SPARC]], [[MIPS architecture|MIPS]], [[PowerPC]]

| size =

| programming language = [[C (programming language)|C]], [[C++]]

| genre = [[Database engine]]

| license = [[GNU General Public License]]

| website =

}}

The MySQL '''Archive storage engine''' is a storage engine for the [[MySQL]] [[relational database management system]]. ItUsers iscan anuse this analytic storage engine which allows a user to create a table whichthat is "archive"“archive” only. NoData data cancannot be deleted from thethis table, only added. The Archive engine uses a compression strategy based aroundon the [[Zlibzlib]] library. Itand takes a row andit packs itthe byrows using a bit header to represent nulls and removes all whitespace for character type fields. OnceWhen this is donecompleted, the row is then inserted into the compression buffer and waits to be flushed to disk based on eitherby an explicit flush table, a read, or by the closing of the table.

One of the current restrictions of Archive tables is that they do not support any indexes, thus necessitating a table scan for any SELECT tasks. Archive tables, however, are supported by the MySQL Query Cache, which can dramatically reduce response times for Archive table queries that are repetitively issued.<ref>https://web.archive.org/web/20100212100829/http://dev.mysql.com/tech-resources/articles/storage-engine.html The MySQL 5.0 Archive Storage Engine (archive date 20100212)</ref> MySQL is examining index support for Archive tables in upcoming releases.

The engine is not durable, and it is not ACID compliant. Unlike [[OLTP]] engines it uses a "stream" format to disk with no block boundaries. The head of the file generated is a byte array representing the data format and contents of the file.

The engine is not durable, and it is not [[ACID]] compliant. Unlike [[OLTP]] engines, it uses a "stream" format to disk with no block boundaries. The head of the Archive file generated is a byte array representing the data format and contents of that file. In MySQL 5.1, a copy of the MySQL FRM file is stored in the header of each Archive file. The FRM file, which represents the definition of a table, allows an Archive file to be restored to a MySQL server if the Archive file is copied to the server.

Despite its use of zlib it is not compatible with gzio, the basis of the gzip tools. It uses its own azio system which is a fork of gzio.

Despite itsthe use of [[zlib]], archive itfiles isare not compatible with [[gzio]], the basis of the [[gzip]] tools. It uses its own azio system whichthat is a fork of gzio.

It differs from the other MySQL analytical engine [MYSQL MyISAM] by being a row level locking engine and by the fact that it keeps a constant version snapshot throughout a single query (making it [MVCC]). This means that Archive will not lock for concurrent bulk inserts. For bulk inserts it performs an interlaced INSERT, so unlike MyISAM order is not guaranteed.

ItArchive differs from the other MySQL analytical engine, [MYSQL [MyISAM]], by being a row -level locking engine and by the fact that it keepskeeping a constant version snapshot throughout a single query (making it [[Multiversion concurrency control|MVCC]]). This means that Archive willdoes not lock for concurrent bulk inserts. For bulk inserts it performs an interlaced INSERT, so unlike MyISAM, order is not guaranteed.

To create an Archive table, one has to specify the engine string:

Users can use the archive_reader tool to take an online snapshot of a table and to change the characteristics of an archive file.

create table t1 (

a int,

b varchar(32))

ENGINE=ARCHIVE

To create an Archive table, one has to specify the following engine string:

The MySQL Archive Storage Engine was authored and is maintained by Brian Aker. It was introduced in 2004 with MySQL 4.1.

<syntaxhighlight lang="mysql">

create table t1 (

a int,

b varchar(32))

ENGINE=ARCHIVE

</syntaxhighlight>

The MySQL <ref>[https://www.w3schools.blog/ MySQL Tutorial]</ref> Archive Storage Engine was authored and is maintained by [[Brian Aker]]. It was introduced in 2004 with MySQL 4.1.

==References==

{{Reflist}}

==External links==

*[http://dev.mysql.com/doc/refman/5.1/en/archive-storage-engine.html MySQL Documentation on Archive Storage Engine]

{{MySQL}}

[[Category:Database engines]]

[[Category:MySQL]]

{{database-software-stub}}