# AWS Athena
Supported since 5.0.2.
# Limitations & Exceptions
Athena does not provide information about integrity constraints. Make sure to provide this information in order to avoid very inefficient queries. We recommend using lenses for this purpose.
- The Simba Athena JDBC does not support the use of default databases when connecting to Athena.
- Accessing object fields with the "dot operator" is not supported (see below).
# Database Connection
The following shows the content of a sample
.properties file that can be used to connect Ontop to Athena:
jdbc.url = jdbc:awsathena://AwsRegion=eu-central-1;S3OutputLocation=s3://result-location jdbc.user = user jdbc.password = password jdbc.driver = com.simba.athena.jdbc.Driver
# Nested Type Support
Ontop implements explicit compatibility with the Athena array type
ARRAY<T>. When used with the flatten lens, it is able to automatically infer the type of the result column.
The flatten lens cannot be used on arrays stored as JSON-encoded columns in the database. For such use cases, the column first has to be converted to an array type.
# Struct Access
MAP objects can be accessed by SQL expressions in the dialect's default way:
SELECT my_struct['my_attribute'] FROM ...
ROW objects, can also be accessed using the
[key] operator. Please note, that in this case,
key must be an integer index instead of the name of the field:
SELECT my_struct FROM ...
Accessing object fields using the "dot operator" is not supported. Please use the
 operator instead.