Data Lake database schemas

The Data Lake incorporates these schemas to separate data sets:

• Default

  The Data Lake data schema is Default. All the data objects that are stored in the Data Lake, and registered in the Data Catalog, are retrieved from the Default schema.

• DataCatalog

  The Data Catalog schema contains Data Catalog data. Currently, the Data Catalog contains the Locale Selections, which are defined in the Data Catalog, Locale Selections function. Use the DataCatalog Locale Selections query to retrieve the locale codes, positions, and substitute locales.

  See Queries for localized data.

• Information_Schema

  The Information_Schema schema contains the schemata, tables, and columns for Data Lake objects.

Use these queries to retrieve values:

• Syntax:

  select * from information_schema.schemata

• Syntax:

  select * from information_schema.tables

To retrieve a list of data objects that are registered in the Data Catalog:

select * from information_schema.tables where table_schema='default'

To retrieve a list of properties for a data object:

select * from information_schema.columns where table_schema='default'  and table_name='object'

If you are selecting column names or table names from information_schema, regardless of the object or property names defined in Data Catalog, the table and column names are in lower case.

select * from information_schema.tables order by table_name
select * from information_schema.columns order by column_name

Note that the columns data depends on Compass query activity. If a data object has not been referenced in a query, the column meta data is not included in the results.