Hive catalog

A Hive catalog is a kind of external catalog that enables you to query data from Apache Hive™ without ingestion.

Also, you can directly transform and load data from Hive by using INSERT INTO based on Hive catalogs. StarRocks supports Hive catalogs from v2.4 onwards.

To ensure successful SQL workloads on your Hive cluster, your StarRocks cluster must be able to access the storage system and metastore of your Hive cluster. StarRocks supports the following storage systems and metastores:

• Object storage or distributed file system like AWS S3 or HDFS
• Metastore like Hive metastore or AWS Glue

Usage notes

• The file formats of Hive that StarRocks supports are Parquet, ORC, and Textfile:

  • Parquet files support the following compression formats: SNAPPY, LZ4, ZSTD, GZIP, and NO_COMPRESSION.
  • ORC files support the following compression formats: ZLIB, SNAPPY, LZO, LZ4, ZSTD, and NO_COMPRESSION.

• The data types of Hive that StarRocks does not support are INTERVAL, BINARY, and UNION. Additionally, StarRocks does not support the MAP and STRUCT data types for Textfile-formatted Hive tables.

• You can only use Hive catalogs to query data. You cannot use Hive catalogs to drop, delete, or insert data into your Hive cluster.

Integration preparations

Before you create a Hive catalog, make sure your StarRocks cluster can integrate with the storage system and metastore of your Hive cluster.

AWS IAM

If your Hive cluster uses AWS S3 as storage or AWS Glue as metastore, choose your suitable authentication method and make the required preparations to ensure that your StarRocks cluster can access the related AWS cloud resources.

The following authentication methods are recommended:

• Instance profile
• Assumed role
• IAM user

Of the above-mentioned three authentication methods, instance profile is the most widely used.

For more information, see Preparation for authentication in AWS IAM.

HDFS

If you choose HDFS as storage, configure your StarRocks cluster as follows:

• (Optional) Set the username that is used to access your HDFS cluster and Hive metastore. By default, StarRocks uses the username of the FE and BE processes to access your HDFS cluster and Hive metastore. You can also set the username by adding export HADOOP_USER_NAME="<user_name>" at the beginning of the fe/conf/hadoop_env.sh file of each FE and at the beginning of the be/conf/hadoop_env.sh file of each BE. After you set the username in these files, restart each FE and each BE to make the parameter settings take effect. You can set only one username for each StarRocks cluster.

• When you query Hive data, the FEs and BEs of your StarRocks cluster use the HDFS client to access your HDFS cluster. In most cases, you do not need to configure your StarRocks cluster to achieve that purpose, and StarRocks starts the HDFS client using the default configurations. You need to configure your StarRocks cluster only in the following situations:

  • High availability (HA) is enabled for your HDFS cluster: Add the hdfs-site.xml file of your HDFS cluster to the $FE_HOME/conf path of each FE and to the $BE_HOME/conf path of each BE.
  • View File System (ViewFs) is enabled for your HDFS cluster: Add the core-site.xml file of your HDFS cluster to the $FE_HOME/conf path of each FE and to the $BE_HOME/conf path of each BE.

NOTE

If an error indicating an unknown host is returned when you send a query, you must add the mapping between the host names and IP addresses of your HDFS cluster nodes to the /etc/hosts path.

Kerberos authentication

If Kerberos authentication is enabled for your HDFS cluster or Hive metastore, configure your StarRocks cluster as follows:

• Run the kinit -kt keytab_path principal command on each FE and each BE to obtain Ticket Granting Ticket (TGT) from Key Distribution Center (KDC). To run this command, you must have the permissions to access your HDFS cluster and Hive metastore. Note that accessing KDC with this command is time-sensitive. Therefore, you need to use cron to run this command periodically.
• Add JAVA_OPTS="-Djava.security.krb5.conf=/etc/krb5.conf" to the $FE_HOME/conf/fe.conf file of each FE and to the $BE_HOME/conf/be.conf file of each BE. In this example, /etc/krb5.conf is the save path of the krb5.conf file. You can modify the path based on your needs.

Create a Hive catalog

Syntax

CREATE EXTERNAL CATALOG <catalog_name>
[COMMENT <comment>]
PROPERTIES
(
    "type" = "hive",
    GeneralParams,
    MetastoreParams,
    StorageCredentialParams,
    MetadataUpdateParams
)

Parameters

catalog_name

The name of the Hive catalog. The naming conventions are as follows:

• The name can contain letters, digits (0-9), and underscores (_). It must start with a letter.
• The name is case-sensitive and cannot exceed 1023 characters in length.

comment

The description of the Hive catalog. This parameter is optional.

type

The type of your data source. Set the value to hive.

GeneralParams

A set of general parameters.

The following table describes the parameters you can configure in GeneralParams.

Parameter	Required	Description
enable_recursive_listing	No	Specifies whether StarRocks reads data from a table and its partitions and from the subdirectories within the physical locations of the table and its partitions. Valid values: true and false. Default value: true. The value true specifies to recursively list subdirectories, and the value false specifies to ignore subdirectories.

MetastoreParams

A set of parameters about how StarRocks integrates with the metastore of your data source.

Hive metastore

If you choose Hive metastore as the metastore of your data source, configure MetastoreParams as follows:

"hive.metastore.type" = "hive",
"hive.metastore.uris" = "<hive_metastore_uri>"

NOTE

Before querying Hive data, you must add the mapping between the host names and IP addresses of your Hive metastore nodes to the /etc/hosts path. Otherwise, StarRocks may fail to access your Hive metastore when you start a query.

The following table describes the parameter you need to configure in MetastoreParams.

Parameter	Required	Description
hive.metastore.type	Yes	The type of metastore that you use for your Hive cluster. Set the value to hive.
hive.metastore.uris	Yes	The URI of your Hive metastore. Format: thrift://<metastore_IP_address>:<metastore_port>. If high availability (HA) is enabled for your Hive metastore, you can specify multiple metastore URIs and separate them with commas (,), for example, "thrift://<metastore_IP_address_1>:<metastore_port_1>,thrift://<metastore_IP_address_2>:<metastore_port_2>,thrift://<metastore_IP_address_3>:<metastore_port_3>".

AWS Glue

If you choose AWS Glue as the metastore of your data source, take one of the following actions:

• To choose the instance profile-based authentication method, configure MetastoreParams as follows:

  "hive.metastore.type" = "glue",
  "aws.glue.use_instance_profile" = "true",
  "aws.glue.region" = "<aws_glue_region>"

• To choose the assumed role-based authentication method, configure MetastoreParams as follows:

  "hive.metastore.type" = "glue",
  "aws.glue.use_instance_profile" = "true",
  "aws.glue.iam_role_arn" = "<iam_role_arn>",
  "aws.glue.region" = "<aws_glue_region>"

• To choose the IAM user-based authentication method, configure MetastoreParams as follows:

  "hive.metastore.type" = "glue",
  "aws.glue.use_instance_profile" = "false",
  "aws.glue.access_key" = "<iam_user_access_key>",
  "aws.glue.secret_key" = "<iam_user_secret_key>",
  "aws.glue.region" = "<aws_s3_region>"

The following table describes the parameters you need to configure in MetastoreParams.

Parameter	Required	Description
hive.metastore.type	Yes	The type of metastore that you use for your Hive cluster. Set the value to glue.
aws.glue.use_instance_profile	Yes	Specifies whether to enable the instance profile-based authentication method and the assumed role-based authentication. Valid values: true and false. Default value: false.
aws.glue.iam_role_arn	No	The ARN of the IAM role that has privileges on your AWS Glue Data Catalog. If you use the assumed role-based authentication method to access AWS Glue, you must specify this parameter.
aws.glue.region	Yes	The region in which your AWS Glue Data Catalog resides. Example: us-west-1.
aws.glue.access_key	No	The access key of your AWS IAM user. If you use the IAM user-based authentication method to access AWS Glue, you must specify this parameter.
aws.glue.secret_key	No	The secret key of your AWS IAM user. If you use the IAM user-based authentication method to access AWS Glue, you must specify this parameter.

For information about how to choose an authentication method for accessing AWS Glue and how to configure an access control policy in the AWS IAM Console, see Authentication parameters for accessing AWS Glue.

StorageCredentialParams

A set of parameters about how StarRocks integrates with your storage system. This parameter set is optional.

You need to configure StorageCredentialParams only when your Hive cluster uses AWS S3 as storage.

If your Hive cluster uses any other storage system, you can ignore StorageCredentialParams.

AWS S3

If you choose AWS S3 as storage for your Hive cluster, take one of the following actions:

• To choose the instance profile-based authentication method, configure StorageCredentialParams as follows:

  "aws.s3.use_instance_profile" = "true",
  "aws.s3.region" = "<aws_s3_region>"

• To choose the assumed role-based authentication method, configure StorageCredentialParams as follows:

  "aws.s3.use_instance_profile" = "true",
  "aws.s3.iam_role_arn" = "<iam_role_arn>",
  "aws.s3.region" = "<aws_s3_region>"

• To choose the IAM user-based authentication method, configure StorageCredentialParams as follows:

  "aws.s3.use_instance_profile" = "false",
  "aws.s3.access_key" = "<iam_user_access_key>",
  "aws.s3.secret_key" = "<iam_user_secret_key>",
  "aws.s3.region" = "<aws_s3_region>"

The following table describes the parameters you need to configure in StorageCredentialParams.

Parameter	Required	Description
aws.s3.use_instance_profile	Yes	Specifies whether to enable the instance profile-based authentication method and the assumed role-based authentication method. Valid values: true and false. Default value: false.
aws.s3.iam_role_arn	No	The ARN of the IAM role that has privileges on your AWS S3 bucket. If you use the assumed role-based authentication method to access AWS S3, you must specify this parameter.
aws.s3.region	Yes	The region in which your AWS S3 bucket resides. Example: us-west-1.
aws.s3.access_key	No	The access key of your IAM user. If you use the IAM user-based authentication method to access AWS S3, you must specify this parameter.
aws.s3.secret_key	No	The secret key of your IAM user. If you use the IAM user-based authentication method to access AWS S3, you must specify this parameter.

For information about how to choose an authentication method for accessing AWS S3 and how to configure an access control policy in AWS IAM Console, see Authentication parameters for accessing AWS S3.

S3-compatible storage system

Hive catalogs support S3-compatible storage systems from v2.5 onwards.

If you choose an S3-compatible storage system, such as MinIO, as storage for your Hive cluster, configure StorageCredentialParams as follows to ensure a successful integration:

"aws.s3.enable_ssl" = "{true | false}",
"aws.s3.enable_path_style_access" = "{true | false}",
"aws.s3.endpoint" = "<s3_endpoint>",
"aws.s3.access_key" = "<iam_user_access_key>",
"aws.s3.secret_key" = "<iam_user_secret_key>"

The following table describes the parameters you need to configure in StorageCredentialParams.

Parameter	Required	Description
aws.s3.enable_ssl	Yes	Specifies whether to enable SSL connection. Valid values: true and false. Default value: true.
aws.s3.enable_path_style_access	Yes	Specifies whether to enable path-style access. Valid values: true and false. Default value: false. For MinIO, you must set the value to true. Path-style URLs use the following format: https://s3.<region_code>.amazonaws.com/<bucket_name>/<key_name>. For example, if you create a bucket named DOC-EXAMPLE-BUCKET1 in the US West (Oregon) Region, and you want to access the alice.jpg object in that bucket, you can use the following path-style URL: https://s3.us-west-2.amazonaws.com/DOC-EXAMPLE-BUCKET1/alice.jpg.
aws.s3.endpoint	Yes	The endpoint that is used to connect to your S3-compatible storage system instead of AWS S3.
aws.s3.access_key	Yes	The access key of your IAM user.
aws.s3.secret_key	Yes	The secret key of your IAM user.

MetadataUpdateParams

A set of parameters about how StarRocks updates the cached metadata of Hive. This parameter set is optional.

StarRocks implements the automatic asynchronous update policy by default.

In most cases, you can ignore MetadataUpdateParams and do not need to tune the policy parameters in it, because the default values of these parameters already provide you with an out-of-the-box performance.

However, if the frequency of data updates in Hive is high, you can tune these parameters to further optimize the performance of automatic asynchronous updates.

NOTE

In most cases, if your Hive data is updated at a granularity of 1 hour or less, the data update frequency is considered high.

Parameter	Required	Description
enable_metastore_cache	No	Specifies whether StarRocks caches the metadata of Hive tables. Valid values: true and false. Default value: true. The value true enables the cache, and the value false disables the cache.
enable_remote_file_cache	No	Specifies whether StarRocks caches the metadata of the underlying data files of Hive tables or partitions. Valid values: true and false. Default value: true. The value true enables the cache, and the value false disables the cache.
metastore_cache_refresh_interval_sec	No	The time interval at which StarRocks asynchronously updates the metadata of Hive tables or partitions cached in itself. Unit: seconds. Default value: 7200, which is 2 hours.
remote_file_cache_refresh_interval_sec	No	The time interval at which StarRocks asynchronously updates the metadata of the underlying data files of Hive tables or partitions cached in itself. Unit: seconds. Default value: 60.
metastore_cache_ttl_sec	No	The time interval at which StarRocks automatically discards the metadata of Hive tables or partitions cached in itself. Unit: seconds. Default value: 86400, which is 24 hours.
remote_file_cache_ttl_sec	No	The time interval at which StarRocks automatically discards the metadata of the underlying data files of Hive tables or partitions cached in itself. Unit: seconds. Default value: 129600, which is 36 hours.
enable_cache_list_names	No	Specifies whether StarRocks caches Hive partition names. Valid values: true and false. Default value: false. The value true enables the cache, and the value false disables the cache.

Examples

The following examples create a Hive catalog named hive_catalog_hms or hive_catalog_glue, depending on the type of metastore you use, to query data from your Hive cluster.

HDFS

If you use HDFS as storage, run a command like below:

CREATE EXTERNAL CATALOG hive_catalog_hms
PROPERTIES
(
    "type" = "hive",
    "hive.metastore.type" = "hive",
    "hive.metastore.uris" = "thrift://xx.xx.xx.xx:9083"
);

AWS S3

Instance profile-based authentication

• If you use Hive metastore in your Hive cluster, run a command like below:

  CREATE EXTERNAL CATALOG hive_catalog_hms
  PROPERTIES
  (
      "type" = "hive",
      "hive.metastore.type" = "hive",
      "hive.metastore.uris" = "thrift://xx.xx.xx.xx:9083",
      "aws.s3.use_instance_profile" = "true",
      "aws.s3.region" = "us-west-2"
  );

• If you use AWS Glue in your Amazon EMR Hive cluster, run a command like below:

  CREATE EXTERNAL CATALOG hive_catalog_glue
  PROPERTIES
  (
      "type" = "hive",
      "hive.metastore.type" = "glue",
      "aws.glue.use_instance_profile" = "true",
      "aws.glue.region" = "us-west-2",
      "aws.s3.use_instance_profile" = "true",
      "aws.s3.region" = "us-west-2"
  );

Assumed role-based authentication

• If you use Hive metastore in your Hive cluster, run a command like below:

  CREATE EXTERNAL CATALOG hive_catalog_hms
  PROPERTIES
  (
      "type" = "hive",
      "hive.metastore.type" = "hive",
      "hive.metastore.uris" = "thrift://xx.xx.xx.xx:9083",
      "aws.s3.use_instance_profile" = "true",
      "aws.s3.iam_role_arn" = "arn:aws:iam::081976408565:role/test_s3_role",
      "aws.s3.region" = "us-west-2"
  );

• If you use AWS Glue in your Amazon EMR Hive cluster, run a command like below:

  CREATE EXTERNAL CATALOG hive_catalog_glue
  PROPERTIES
  (
      "type" = "hive",
      "hive.metastore.type" = "glue",
      "aws.glue.use_instance_profile" = "true",
      "aws.glue.iam_role_arn" = "arn:aws:iam::081976408565:role/test_glue_role",
      "aws.glue.region" = "us-west-2",
      "aws.s3.use_instance_profile" = "true",
      "aws.s3.iam_role_arn" = "arn:aws:iam::081976408565:role/test_s3_role",
      "aws.s3.region" = "us-west-2"
  );

IAM user-based authentication

• If you use Hive metastore in your Hive cluster, run a command like below:

  CREATE EXTERNAL CATALOG hive_catalog_hms
  PROPERTIES
  (
      "type" = "hive",
      "hive.metastore.type" = "hive",
      "hive.metastore.uris" = "thrift://xx.xx.xx.xx:9083",
      "aws.s3.use_instance_profile" = "false",
      "aws.s3.access_key" = "<iam_user_access_key>",
      "aws.s3.secret_key" = "<iam_user_access_key>",
      "aws.s3.region" = "us-west-2"
  );

• If you use AWS Glue in your Amazon EMR Hive cluster, run a command like below:

  CREATE EXTERNAL CATALOG hive_catalog_glue
  PROPERTIES
  (
      "type" = "hive",
      "hive.metastore.type" = "glue",
      "aws.glue.use_instance_profile" = "false",
      "aws.glue.access_key" = "<iam_user_access_key>",
      "aws.glue.secret_key" = "<iam_user_secret_key>",
      "aws.glue.region" = "us-west-2",
      "aws.s3.use_instance_profile" = "false",
      "aws.s3.access_key" = "<iam_user_access_key>",
      "aws.s3.secret_key" = "<iam_user_secret_key>",
      "aws.s3.region" = "us-west-2"
  );

S3-compatible storage system

Use MinIO as an example. Run a command like below:

CREATE EXTERNAL CATALOG hive_catalog_hms
PROPERTIES
(
    "type" = "hive",
    "hive.metastore.type" = "hive",
    "hive.metastore.uris" = "thrift://xx.xx.xx.xx:9083",
    "aws.s3.enable_ssl" = "true",
    "aws.s3.enable_path_style_access" = "true",
    "aws.s3.endpoint" = "<s3_endpoint>",
    "aws.s3.access_key" = "<iam_user_access_key>",
    "aws.s3.secret_key" = "<iam_user_secret_key>"
);

View the schema of a Hive table

You can use one of the following syntaxes to view the schema of a Hive table:

• View schema

  DESC[RIBE] <catalog_name>.<database_name>.<table_name>

• View schema and location from the CREATE statement

  SHOW CREATE TABLE <catalog_name>.<database_name>.<table_name>

Query a Hive table

1. Use the following syntax to view the databases in your Hive cluster:

   SHOW DATABASES FROM <catalog_name>

2. Use the following syntax to connect to your target Hive database:

   USE <catalog_name>.<database_name>

3. Use the following syntax to query the Hive table:

   SELECT count(*) FROM <table_name> LIMIT 10

Load data from Hive

Suppose you have an OLAP table named olap_tbl, you can transform and load data like below:

INSERT INTO default_catalog.olap_db.olap_tbl SELECT * FROM hive_table

Manually or automatically update metadata cache

Manual update

By default, StarRocks caches the metadata of Hive and automatically updates the metadata in asynchronous mode to deliver better performance. Additionally, after some schema changes or table updates are made on a Hive table, you can also use REFRESH EXTERNAL TABLE to manually update its metadata, thereby ensuring that StarRocks can obtain up-to-date metadata at its earliest opportunity and generate appropriate execution plans:

REFRESH EXTERNAL TABLE <table_name>

You need to manually update metadata in the following situations:

• A data file in an existing partition is changed, for example, by running the INSERT OVERWRITE ... PARTITION ... command.

• Schema changes are made on a Hive table.

• An existing Hive table is deleted by using the DROP statement, and a new Hive table with the same name as the deleted Hive table is created.

• You have specified "enable_cache_list_names" = "true" in PROPERTIES at the creation of your Hive catalog, and you want to query new partitions that you just created on your Hive cluster.

  NOTE

  From v2.5.5 onwards, StarRocks provides the periodic Hive metadata cache refresh feature. For more information, see the below "Periodically refresh metadata cache" section of this topic. After you enable this feature, StarRocks refreshes your Hive metadata cache every 10 minutes by default. Therefore, manual updates are not needed in most cases. You need to perform a manual update only when you want to query new partitions immediately after the new partitions are created on your Hive cluster.

Note that the REFRESH EXTERNAL TABLE refreshes only the tables and partitions cached in your FEs.

Periodically refresh metadata cache

From v2.5.5 onwards, StarRocks can periodically refresh the cached metadata of the frequently accessed Hive catalogs to perceive data changes. You can configure the Hive metadata cache refresh through the following FE parameters:

Configuration item	Default	Description
enable_background_refresh_connector_metadata	true in v3.0 false in v2.5	Whether to enable the periodic Hive metadata cache refresh. After it is enabled, StarRocks polls the metastore (Hive Metastore or AWS Glue) of your Hive cluster, and refreshes the cached metadata of the frequently accessed Hive catalogs to perceive data changes. true indicates to enable the Hive metadata cache refresh, and false indicates to disable it. This item is an FE dynamic parameter. You can modify it using the ADMIN SET FRONTEND CONFIG command.
background_refresh_metadata_interval_millis	600000 (10 minutes)	The interval between two consecutive Hive metadata cache refreshes. Unit: millisecond. This item is an FE dynamic parameter. You can modify it using the ADMIN SET FRONTEND CONFIG command.
background_refresh_metadata_time_secs_since_last_access_secs	86400 (24 hours)	The expiration time of a Hive metadata cache refresh task. For the Hive catalog that has been accessed, if it has not been accessed for more than the specified time, StarRocks stops refreshing its cached metadata. For the Hive catalog that has not been accessed, StarRocks will not refresh its cached metadata. Unit: second. This item is an FE dynamic parameter. You can modify it using the ADMIN SET FRONTEND CONFIG command.
Using the periodic Hive metadata cache refresh feature and the metadata automatic asynchronous update policy together significantly accelerates data access, reduces the read load from external data sources, and improves query performance.

Appendix: Understand automatic asynchronous update

Automatic asynchronous update is the default policy that StarRocks uses to update the metadata in Hive catalogs.

By default (namely, when the enable_metastore_cache and enable_remote_file_cache parameters are both set to true), if a query hits a partition of a Hive table, StarRocks automatically caches the metadata of the partition and the metadata of the underlying data files of the partition. The cached metadata is updated by using the lazy update policy.

For example, there is a Hive table named table2, which has four partitions: p1, p2, p3, and p4. A query hits p1, and StarRocks caches the metadata of p1 and the metadata of the underlying data files of p1. Assume that the default time intervals to update and discard the cached metadata are as follows:

• The time interval (specified by the metastore_cache_refresh_interval_sec parameter) to asynchronously update the cached metadata of p1 is 2 hours.
• The time interval (specified by the remote_file_cache_refresh_interval_sec parameter) to asynchronously update the cached metadata of the underlying data files of p1 is 60 seconds.
• The time interval (specified by the metastore_cache_ttl_sec parameter) to automatically discard the cached metadata of p1 is 24 hours.
• The time interval (specified by the remote_file_cache_ttl_sec parameter) to automatically discard the cached metadata of the underlying data files of p1 is 36 hours.

The following figure shows the time intervals on a timeline for easier understanding.

Then StarRocks updates or discards the metadata in compliance with the following rules:

• If another query hits p1 again and the current time from the last update is less than 60 seconds, StarRocks does not update the cached metadata of p1 or the cached metadata of the underlying data files of p1.
• If another query hits p1 again and the current time from the last update is more than 60 seconds, StarRocks updates the cached metadata of the underlying data files of p1.
• If another query hits p1 again and the current time from the last update is more than 2 hours, StarRocks updates the cached metadata of p1.
• If p1 has not been accessed within 24 hours from the last update, StarRocks discards the cached metadata of p1. The metadata will be cached at the next query.
• If p1 has not been accessed within 36 hours from the last update, StarRocks discards the cached metadata of the underlying data files of p1. The metadata will be cached at the next query.