Release Notes for MariaDB ColumnStore 1.4.2
MariaDB ColumnStore is a columnar storage engine. This is the first release in the ColumnStore 1.4 series. This release contains a variety of new features and fixes, compared to MariaDB ColumnStore 1.2.5.
MariaDB ColumnStore 1.4.2 was released on 2020-01-06.
MariaDB Server Convergence
Until now, MariaDB ColumnStore has been maintained as a custom fork of MariaDB Server, to handle the unique way that queries are handled for distributed processing.
With this release, a joint project between the MariaDB Server and MariaDB ColumnStore engineering teams, ColumnStore now works as a pluggable storage engine on the standard MariaDB Enterprise Server 10.4 platform.
MariaDB Enterprise Server 10.4 includes distributed processing engine support features. These features are not present in the older 10.3 and 10.2 release series.
A standard MariaDB Server is now used for ColumnStore UM (User Module) nodes. ColumnStore users can now enjoy the benefits of MariaDB Server 10.4, and MariaDB Server 10.4 users are now able to deploy ColumnStore on top of their existing stack.
S3 Storage Manager
MariaDB ColumnStore now has the ability to use any object store that is Amazon S3 API compatible. The new Storage Manager uses a persistent disk cache for read/write operations so that it has minimal performance impact on ColumnStore. In some cases it will perform better than local disk operations.
postConfigure, edit the storagemanager.cnf configuration file to specify the S3 connection parameters (as detailed in the S3 section of that file), and the local machine configuration (as detailed in the ObjectStorage and Cache sections). The configuration file is documented in-line. Enable the Storage Manager by setting ObjectStorage/Service to
postConfigure, and when promoted for type of storage, select the
cpimport S3 Support
S3 Authentication Key
S3 Secret Key
S3 Hostname (omit if using Amazon S3, this is the default)
When these options are set, cpimport will use the path/filename provided to load an object from object storage instead of a local file. Current behavior is to download the entire file into memory before processing.
Expanded Data Type Support
Please note that for cpimport the current system time of the PM node is used.
MODA() Mode Average UDAF
MODA() UDAF (User-Defined Aggregate Function) determines the mode average.
MODA() has tie-break behavior to use the closest to the average, and then the smallest absolute value.
Statement-Based Replication Support
Statement-based replication into ColumnStore tables is supported by setting
columnstore_replication_slave=on on the UM that will apply the replication data. Row-based replication events on ColumnStore replica (slave) tables will currently fail, generating an error viewable with SHOW SLAVE STATUS
The performance of BRM (Block Resolution Manager) snapshots has been increased for improved performance when committing data to ColumnStore.
To reduce SSD wear and and increase write performance for large data sets containing many columns, ColumnStore now allocates disk as-needed, writing only real data and padding to fill the remainder of an 8KB block. ColumnStore previously wrote twice -- once to pre-allocate an empty file for each new extent (8 million item file for a column), and a second time to fill the file with real data.
The outer "ORDER BY" of a query is now processed using ColumnStore's engine instead of MariaDB server. This uses a faster sorting algorithm for higher performance with larger result sets.
Joins use a new hash algorithm which is significantly faster and requires significantly less initial memory to execute.
Memory cleanup after query execution now occurs in a separate thread. This previously occurred in the main ExeMgr thread, which could delay execution of new queries.
InfiniDB Alias Eliminated
ColumnStore 1.2 and earlier included the InfiniDB engine as an alias. This alias has now been removed. All ColumnStore tables must now be created with the engine name "columnstore". All MariaDB system variables prefixed with "infinidb_
vtable Replaced by Query Execution Handlers
vtable has been replaced with a set of query execution handlers:
Derived Handler, and table API mode.
Select Handler is the replacement for a vtable, and is the default query execution handler. It is expected to provide the fastest execution path for the whole query.
Select Handler lacks support for some vtable features, including:
INSERT .. SELECT
SELECT INTO OUTFILE
Select Handler fails to execute a query, an error is returned. If a query fails under the
Select Handler, set
columnstore_select_handler=off for the session. This will cause the Server to hand-off query execution to the
Derived Handler. The query must be restarted after the session variable has been set.
Derived Handler fails to execute a query, an error is returned. If a query fails under both the
Select Handler and
Derived Handler, set
columnstore_derived_handler=off for the session. This will cause table API execution, an equivalent to disabled vtable mode in ColumnStore 1.2.x and earlier. The query must be restarted after the session variables have been set.
ColumnStore 1.4 is included with MariaDB Enterprise Server 10.4 on select Platforms.
ColumnStore is available for deployment from package tarball and repository. ColumnStore is not available for deployment from binary tarballs.
"Distributed Install" Method Eliminated
The "distributed install" method which pushed packages onto other nodes during
postConfigure has been removed. ColumnStore packages must now be installed on all nodes prior to startup.
Configuration Path Changes
ColumnStore XML configuration files have moved to
MariaDB Enterprise Server configuration options for ColumnStore have moved to
/etc/my.cnf.d/columnstore.cnf and the default MariaDB Enterprise Server
my.cnf will load this file.
Data Directory Path Change
The ColumnStore data directory has moved to
/var/lib/columnstore and is separate from the MariaDB Server data directory at
Executable Path Changes
ColumnStore binaries have moved to
/usr/sbin, and the libraries are in the OS standard
/usr library path. Some ColumnStore binaries have been renamed to avoid conflict, including:
User Account for Cross-Engine Joins
Cross-engine joins depend on TCP connection from
ExeMgr to the Server process. Since the database
root user in MariaDB Enterprise Server 10.4 authenticates only by UNIX socket, a dedicated user must be created to support cross-engine joins. The cross engine section of
Columnstore.xml should be edited accordingly.
Can result in data loss
DBRM files could be deleted during a failover scenario. (MCOL-2152)
Can result in a hang or crash
Certain window function queries could crash the Server process. (MCOL-3434)
Can result in unexpected behavior
DISTINCTconcatenates even non-distinct values. (MCOL-2146)
Wrong results could be returned for a complex query with subquery and window functions over
Pipe operator (
|) could return wrong results. (MCOL-174)
Comparison of padded strings could provide incorrect results. (MCOL-1559)
DISTINCTcould be performed in incorrect order relative to Window functions and
Cross-engine joins with query using
Bulk write API writes were possible when writes were suspended. (MCOL-3576)
JOINcould significantly waste memory. (MCOL-1758)
Memory leaks. (MCOL-3621)
Related to install and upgrade
Cosmetic typo in
postConfigureoutput. Output upon success is now
MariaDB ColumnStore Install Successfully Completed, System is Active(MCOL-1598)
commit_status variable added hash
versionstatus variable added
compression_system variable added type
decimal_system variable added scale
derived_system variable added handler
diskjoin_system variable added bucketsize
diskjoin_system variable added largesidelimit
diskjoin_system variable added smallsidelimit
double_system variable added for_ decimal_ math
group_system variable added by_ handler
import_system variable added for_ batchinsert_ delimiter
import_system variable added for_ batchinsert_ enclosed_ by
local_system variable added query
orderby_system variable added threads
ordered_system variable added only
replication_system variable added slave
select_system variable added handler
string_system variable added scan_ threshold
stringtable_system variable added threshold
um_system variable added mem_ limit
use_system variable added decimal_ scale
use_system variable added import_ for_ batchinsert
varbin_system variable added always_ hex
COLUMNSinformation schema table added
EXTENTSinformation schema table added
FILESinformation schema table added
TABLESinformation schema table added
mysqld--columnstore-columns command-line option added
mysqld--columnstore-compression-type command-line option added
mysqld--columnstore-decimal-scale command-line option added
mysqld--columnstore-derived-handler command-line option added
mysqld--columnstore-diskjoin-bucketsize command-line option added
mysqld--columnstore-diskjoin-largesidelimit command-line option added
mysqld--columnstore-diskjoin-smallsidelimit command-line option added
mysqld--columnstore-double-for-decimal-math command-line option added
mysqld--columnstore-extents command-line option added
mysqld--columnstore-files command-line option added
mysqld--columnstore-group-by-handler command-line option added
mysqld--columnstore-import-for-batchinsert-delimiter command-line option added
mysqld--columnstore-import-for-batchinsert-enclosed-by command-line option added
mysqld--columnstore-local-query command-line option added
mysqld--columnstore-orderby-threads command-line option added
mysqld--columnstore-ordered-only command-line option added
mysqld--columnstore-replication-slave command-line option added
mysqld--columnstore-select-handler command-line option added
mysqld--columnstore-string-scan-threshold command-line option added
mysqld--columnstore-stringtable-threshold command-line option added
mysqld--columnstore-tables command-line option added
mysqld--columnstore-um-mem-limit command-line option added
mysqld--columnstore-use-decimal-scale command-line option added
mysqld--columnstore-use-import-for-batchinsert command-line option added
mysqld--columnstore-varbin-always-hex command-line option added
mysqld--columnstore command-line option added
In alignment to the MariaDB Corporation Engineering Policy, MariaDB ColumnStore 1.4.2 is provided for:
Red Hat Enterprise Linux 8
Red Hat Enterprise Linux 7
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server 12
MariaDB Enterprise ColumnStore 1.4 is no longer supported. If you would like to deploy Enterprise ColumnStore, please use MariaDB Enterprise ColumnStore 5 or later. For installation and upgrade instructions, see "Deploy".