Amazon Athena Cloudera Impala connector - Amazon Athena
PrerequisitesLimitationsTermsParametersData type supportPartitions and splitsPerformancePassthrough queriesLicense informationAdditional resources

Amazon Athena Cloudera Impala connector

The Amazon Athena Cloudera Impala connector enables Athena to run SQL queries on the Cloudera Impala distribution. The connector transforms your Athena SQL queries to the equivalent Impala syntax.

Prerequisites

Limitations

  • Write DDL operations are not supported.

  • In a multiplexer setup, the spill bucket and prefix are shared across all database instances.

  • Any relevant Lambda limits. For more information, see Lambda quotas in the AWS Lambda Developer Guide.

Terms

The following terms relate to the Cloudera Impala connector.

  • Database instance – Any instance of a database deployed on premises, on Amazon EC2, or on Amazon RDS.

  • Handler – A Lambda handler that accesses your database instance. A handler can be for metadata or for data records.

  • Metadata handler – A Lambda handler that retrieves metadata from your database instance.

  • Record handler – A Lambda handler that retrieves data records from your database instance.

  • Composite handler – A Lambda handler that retrieves both metadata and data records from your database instance.

  • Property or parameter – A database property used by handlers to extract database information. You configure these properties as Lambda environment variables.

  • Connection String – A string of text used to establish a connection to a database instance.

  • Catalog – A non-AWS Glue catalog registered with Athena that is a required prefix for the connection_string property.

  • Multiplexing handler – A Lambda handler that can accept and use multiple database connections.

Parameters

Use the Lambda environment variables in this section to configure the Cloudera Impala connector.

Connection string

Use a JDBC connection string in the following format to connect to an Impala cluster.

impala://${jdbc_connection_string}

Using a multiplexing handler

You can use a multiplexer to connect to multiple database instances with a single Lambda function. Requests are routed by catalog name. Use the following classes in Lambda.

Handler Class
Composite handler ImpalaMuxCompositeHandler
Metadata handler ImpalaMuxMetadataHandler
Record handler ImpalaMuxRecordHandler

Multiplexing handler parameters

Parameter Description
$catalog_connection_string Required. An Impala cluster connection string for an Athena catalog. Prefix the environment variable with the name of the catalog used in Athena. For example, if the catalog registered with Athena is myimpalacatalog, then the environment variable name is myimpalacatalog_connection_string.
default Required. The default connection string. This string is used when the catalog is lambda:${AWS_LAMBDA_FUNCTION_NAME}.

The following example properties are for a Impala MUX Lambda function that supports two database instances: impala1 (the default), and impala2.

Property Value
default impala://jdbc:impala://some.impala.host.name:21050/?${Test/impala1}
impala_catalog1_connection_string impala://jdbc:impala://someother.impala.host.name:21050/?${Test/impala1}
impala_catalog2_connection_string impala://jdbc:impala://another.impala.host.name:21050/?UID=sample&PWD=sample

Providing credentials

To provide a user name and password for your database in your JDBC connection string, you can use connection string properties or AWS Secrets Manager.

  • Connection String – A user name and password can be specified as properties in the JDBC connection string.

    Important

    As a security best practice, do not use hardcoded credentials in your environment variables or connection strings. For information about moving your hardcoded secrets to AWS Secrets Manager, see Move hardcoded secrets to AWS Secrets Manager in the AWS Secrets Manager User Guide.

  • AWS Secrets Manager – To use the Athena Federated Query feature with AWS Secrets Manager, the VPC connected to your Lambda function should have internet access or a VPC endpoint to connect to Secrets Manager.

    You can put the name of a secret in AWS Secrets Manager in your JDBC connection string. The connector replaces the secret name with the username and password values from Secrets Manager.

    For Amazon RDS database instances, this support is tightly integrated. If you use Amazon RDS, we highly recommend using AWS Secrets Manager and credential rotation. If your database does not use Amazon RDS, store the credentials as JSON in the following format:

    {"username": "${username}", "password": "${password}"}
Example connection string with secret name

The following string has the secret name ${Test/impala1host}.

impala://jdbc:impala://Impala1host:21050/?...&${Test/impala1host}&...

The connector uses the secret name to retrieve secrets and provide the user name and password, as in the following example.

impala://jdbc:impala://Impala1host:21050/?...&UID=sample2&PWD=sample2&...

Currently, Cloudera Impala recognizes the UID and PWD JDBC properties.

Using a single connection handler

You can use the following single connection metadata and record handlers to connect to a single Cloudera Impala instance.

Handler type Class
Composite handler ImpalaCompositeHandler
Metadata handler ImpalaMetadataHandler
Record handler ImpalaRecordHandler

Single connection handler parameters

Parameter Description
default Required. The default connection string.

The single connection handlers support one database instance and must provide a default connection string parameter. All other connection strings are ignored.

The following example property is for a single Cloudera Impala instance supported by a Lambda function.

Property Value
default impala://jdbc:impala://Impala1host:21050/?secret=${Test/impala1host}

Spill parameters

The Lambda SDK can spill data to Amazon S3. All database instances accessed by the same Lambda function spill to the same location.

Parameter Description
spill_bucket Required. Spill bucket name.
spill_prefix Required. Spill bucket key prefix.
spill_put_request_headers (Optional) A JSON encoded map of request headers and values for the Amazon S3 putObject request that is used for spilling (for example, {"x-amz-server-side-encryption" : "AES256"}). For other possible headers, see PutObject in the Amazon Simple Storage Service API Reference.

Data type support

The following table shows the corresponding data types for JDBC, Cloudera Impala, and Arrow.

JDBC Cloudera Impala Arrow
Boolean Boolean Bit
Integer TINYINT Tiny
Short SMALLINT Smallint
Integer INT Int
Long BIGINT Bigint
float float4 Float4
Double float8 Float8
Date date DateDay
Timestamp timestamp DateMilli
String VARCHAR Varchar
Bytes bytes Varbinary
BigDecimal Decimal Decimal
ARRAY N/A (see note) List
Note

Currently, Cloudera Impala does not support the aggregate types ARRAY, MAP, STRUCT, or UNIONTYPE. Columns of aggregate types are treated as VARCHAR columns in SQL.

Partitions and splits

Partitions are used to determine how to generate splits for the connector. Athena constructs a synthetic column of type varchar that represents the partitioning scheme for the table to help the connector generate splits. The connector does not modify the actual table definition.

Performance

Cloudera Impala supports static partitions. The Athena Cloudera Impala connector can retrieve data from these partitions in parallel. If you want to query very large datasets with uniform partition distribution, static partitioning is highly recommended. The Cloudera Impala connector is resilient to throttling due to concurrency.

The Athena Cloudera Impala connector performs predicate pushdown to decrease the data scanned by the query. LIMIT clauses, simple predicates, and complex expressions are pushed down to the connector to reduce the amount of data scanned and decrease query execution run time.

LIMIT clauses

A LIMIT N statement reduces the data scanned by the query. With LIMIT N pushdown, the connector returns only N rows to Athena.

Predicates

A predicate is an expression in the WHERE clause of a SQL query that evaluates to a Boolean value and filters rows based on multiple conditions. The Athena Cloudera Impala connector can combine these expressions and push them directly to Cloudera Impala for enhanced functionality and to reduce the amount of data scanned.

The following Athena Cloudera Impala connector operators support predicate pushdown:

  • Boolean: AND, OR, NOT

  • Equality: EQUAL, NOT_EQUAL, LESS_THAN, LESS_THAN_OR_EQUAL, GREATER_THAN, GREATER_THAN_OR_EQUAL, IS_DISTINCT_FROM, NULL_IF, IS_NULL

  • Arithmetic: ADD, SUBTRACT, MULTIPLY, DIVIDE, MODULUS, NEGATE

  • Other: LIKE_PATTERN, IN

Combined pushdown example

For enhanced querying capabilities, combine the pushdown types, as in the following example:

SELECT * 
FROM my_table 
WHERE col_a > 10 
    AND ((col_a + col_b) > (col_c % col_d))
    AND (col_e IN ('val1', 'val2', 'val3') OR col_f LIKE '%pattern%') 
LIMIT 10;

Passthrough queries

The Cloudera Impala connector supports passthrough queries. Passthrough queries use a table function to push your full query down to the data source for execution.

To use passthrough queries with Cloudera Impala, you can use the following syntax:

SELECT * FROM TABLE(
        system.query(
            query => 'query string'
        ))

The following example query pushes down a query to a data source in Cloudera Impala. The query selects all columns in the customer table, limiting the results to 10.

SELECT * FROM TABLE(
        system.query(
            query => 'SELECT * FROM customer LIMIT 10'
        ))

License information

By using this connector, you acknowledge the inclusion of third party components, a list of which can be found in the pom.xml file for this connector, and agree to the terms in the respective third party licenses provided in the LICENSE.txt file on GitHub.com.

Additional resources

For the latest JDBC driver version information, see the pom.xml file for the Cloudera Impala connector on GitHub.com.

For additional information about this connector, visit the corresponding site on GitHub.com.