Querying data using Trino

Default behavior without schema emulation

Schema emulation is disabled by default, placing all Apache Kudu tables in the default schema. The following query rules apply when working in this mode:

• Query an Apache Kudu table named orders in Trino by running SELECT * FROM example.default.orders or SELECT * FROM orders if your active catalog and schema are set to kudu and default.
• Enclose table names in double quotes if they contain special characters, for example,

  SELECT * FROM example.default."special.table!"

The following examples show how to create a table, inspect the table structure, insert data, and query the results in the default schema:

Create the users table:

CREATE TABLE example.default.users (
  user_id int WITH (primary_key = true),
  first_name VARCHAR,
  last_name VARCHAR
) WITH (
  partition_by_hash_columns = ARRAY['user_id'],
  partition_by_hash_buckets = 2
);

Describe the table structure:

DESCRIBE example.default.users;

The query returns the following column metadata:

Insert data into the table:

INSERT INTO example.default.users VALUES (1, 'Donald', 'Duck'), (2, 'Mickey', 'Mouse');

Query the inserted data:

SELECT * FROM example.default.users;

Behavior with schema emulation

When schema emulation is enabled in the catalog configuration file, for example, etc/catalog/example.properties, the connector maps Apache Kudu table names to Trino schemas.

When kudu.schema-emulation.enabledis true and the kudu.schema-emulation.prefix property is empty, the connector uses the following mappings and creates a special table named $schemas to manage schemas:

When kudu.schema-emulation.enabled is true and kudu.schema-emulation.prefix is presto::, the connector uses the following mappings and creates a special table named presto::$schemas to manage schemas: