There are use cases that multiple data sources need to be managed and visited together in one single session or view. Also, users may not care about the distribution and source of data at all. The VDM (Virtualize Data Market) connector is aimed at bringing in this feature to openLooKeng.
The VDM connector supports to:
- Create, update and delete views that combines multiple catalogs
- Visit real data through the views
- Manage user privilege through the views
- Log the use of VDM views by each user
VDM uses openLooKeng metastore to store its database information. It can be stored either on HDFS or relational database, depending on the implementation of openLooKeng metastore.
Therefore metastore must be configured first.
- Here is an example of using RDBMS as metastore, create
# the type of metastore storage hetu.metastore.type=jdbc # jdbc connection address of database hetu.metastore.db.url=jdbc:mysql://.... # the user name of the database hetu.metastore.db.user=root # the password of database hetu.metastore.db.password=123456
Here is an example of using HDFS as metastore，create
Path white list：["/tmp”, “/opt/hetu”, “/opt/openlookeng”, “/etc/hetu”, “/etc/openlookeng”, current workspace]
Notice：avoid to choose root directory; ../ can’t include in path; if you config node.date_dir, then the current workspace is the parent of node.data_dir; otherwise, the current workspace is the openlookeng server’s directory.
# the type of metastore storage hetu.metastore.type=hetufilesystem # profile name of hetu file system hetu.metastore.hetufilesystem.profile-name=hdfs-config-metastore # the path of metastore storage in the hetu file system hetu.metastore.hetufilesystem.path=/etc/openlookeng/metastore
Check filesystem for more information.
For user interface, the connector can be accessed from JDBC or command line interface. Currently VDM only supports schemas and views. Tables are NOT supported.
Schema operations are the same as usual openLooKeng catalogs, including
rename schema and
Views can be created under a specific schema:
create view as ...,
Configure a data source
vdm1 by creating
etc/catalogs with following contents:
This example creates a schema
vdm1 catalog, and creates two views from two other different data sources. Note that metastore must be configured in advance (See usage section).
create schema vdm1.schema1; use vdm1.schema1; create view view1 as select * from mysql.table.test; create view view2 as select * from hive.table.test; select * from view1;
VDM datasource can also be managed through dynamic catalog API. See Dynamic Catalog topic for more information.
All supported CLI queries
|Support operation||External interface (SQL command)|
|Query all VDM|
|Query all schemas under VDM|
|Query all views in the schema|
|Query data by view|
|Query view creation information|
|Query view column information|
|See SQL Statement Syntax topic for more information.|