Metastores#

Object storage access is mediated through a metastore. Metastores provide information on directory structure, file format, and metadata about the stored data. Object storage connectors support the use of one or more metastores. A supported metastore is required to use any object storage connector.

Additional configuration is required in order to access tables with Athena partition projection metadata or implement first class support for Avro tables. These requirements are discussed later in this topic.

General metastore configuration properties#

The following table describes general metastore configuration properties, most of which are used with either metastore.

At a minimum, each Delta Lake, Hive or Hudi object storage catalog file must set the hive.metastore configuration property to define the type of metastore to use. Iceberg catalogs instead use the iceberg.catalog.type configuration property to define the type of metastore to use.

Additional configuration properties specific to the Thrift and Glue Metastores are also available. They are discussed later in this topic.

General metastore configuration properties#

Property Name

Description

Default

hive.metastore

The type of Hive metastore to use. Trino currently supports the default Hive Thrift metastore (thrift), and the AWS Glue Catalog (glue) as metadata sources. You must use this for all object storage catalogs except Iceberg.

thrift

iceberg.catalog.type

The Iceberg table format manages most metadata in metadata files in the object storage itself. A small amount of metadata, however, still requires the use of a metastore. In the Iceberg ecosystem, these smaller metastores are called Iceberg metadata catalogs, or just catalogs. The examples in each subsection depict the contents of a Trino catalog file that uses the the Iceberg connector to configures different Iceberg metadata catalogs.

You must set this property in all Iceberg catalog property files. Valid values are HIVE_METASTORE, GLUE, JDBC, REST, and NESSIE.

hive.metastore-cache.cache-partitions

Enable caching for partition metadata. You can disable caching to avoid inconsistent behavior that results from it.

true

hive.metastore-cache-ttl

Duration of how long cached metastore data is considered valid.

0s

hive.metastore-stats-cache-ttl

Duration of how long cached metastore statistics are considered valid.

5m

hive.metastore-cache-maximum-size

Maximum number of metastore data objects in the Hive metastore cache.

10000

hive.metastore-refresh-interval

Asynchronously refresh cached metastore data after access if it is older than this but is not yet expired, allowing subsequent accesses to see fresh data.

hive.metastore-refresh-max-threads

Maximum threads used to refresh cached metastore data.

10

hive.hide-delta-lake-tables

Controls whether to hide Delta Lake tables in table listings. Currently applies only when using the AWS Glue metastore.

false

Thrift metastore configuration properties#

In order to use a Hive Thrift metastore, you must configure the metastore with hive.metastore=thrift and provide further details with the following properties:

Thrift metastore configuration properties#

Property name

Description

Default

hive.metastore.uri

The URIs of the Hive metastore to connect to using the Thrift protocol. If a comma-separated list of URIs is provided, the first URI is used by default, and the rest of the URIs are fallback metastores. This property is required. Example: thrift://192.0.2.3:9083 or thrift://192.0.2.3:9083,thrift://192.0.2.4:9083

hive.metastore.username

The username Trino uses to access the Hive metastore.

hive.metastore.authentication.type

Hive metastore authentication type. Possible values are NONE or KERBEROS.

NONE

hive.metastore.thrift.client.connect-timeout

Socket connect timeout for metastore client.

10s

hive.metastore.thrift.client.read-timeout

Socket read timeout for metastore client.

10s

hive.metastore.thrift.impersonation.enabled

Enable Hive metastore end user impersonation.

hive.metastore.thrift.use-spark-table-statistics-fallback

Enable usage of table statistics generated by Apache Spark when Hive table statistics are not available.

true

hive.metastore.thrift.delegation-token.cache-ttl

Time to live delegation token cache for metastore.

1h

hive.metastore.thrift.delegation-token.cache-maximum-size

Delegation token cache maximum size.

1000

hive.metastore.thrift.client.ssl.enabled

Use SSL when connecting to metastore.

false

hive.metastore.thrift.client.ssl.key

Path to private key and client certification (key store).

hive.metastore.thrift.client.ssl.key-password

Password for the private key.

hive.metastore.thrift.client.ssl.trust-certificate

Path to the server certificate chain (trust store). Required when SSL is enabled.

hive.metastore.thrift.client.ssl.trust-certificate-password

Password for the trust store.

hive.metastore.thrift.batch-fetch.enabled

Enable fetching tables and views from all schemas in a single request.

true

hive.metastore.service.principal

The Kerberos principal of the Hive metastore service.

hive.metastore.client.principal

The Kerberos principal that Trino uses when connecting to the Hive metastore service.

hive.metastore.client.keytab

Hive metastore client keytab location.

hive.metastore.thrift.delete-files-on-drop

Actively delete the files for managed tables when performing drop table or partition operations, for cases when the metastore does not delete the files.

false

hive.metastore.thrift.assume-canonical-partition-keys

Allow the metastore to assume that the values of partition columns can be converted to string values. This can lead to performance improvements in queries which apply filters on the partition columns. Partition keys with a TIMESTAMP type do not get canonicalized.

false

hive.metastore.thrift.client.socks-proxy

SOCKS proxy to use for the Thrift Hive metastore.

hive.metastore.thrift.client.max-retries

Maximum number of retry attempts for metastore requests.

9

hive.metastore.thrift.client.backoff-scale-factor

Scale factor for metastore request retry delay.

2.0

hive.metastore.thrift.client.max-retry-time

Total allowed time limit for a metastore request to be retried.

30s

hive.metastore.thrift.client.min-backoff-delay

Minimum delay between metastore request retries.

1s

hive.metastore.thrift.client.max-backoff-delay

Maximum delay between metastore request retries.

1s

hive.metastore.thrift.txn-lock-max-wait

Maximum time to wait to acquire hive transaction lock.

10m

Use the following configuration properties for HTTP client transport mode, so when the hive.metastore.uri uses the http:// or https:// protocol.

Thrift metastore HTTP configuration properties#

Property name

Description

hive.metastore.http.client.authentication.type

The authentication type to use with the HTTP client transport mode. When set to the only supported value of BEARER, the token configured in hive.metastore.http.client.bearer-token is used to authenticate to the metastore service.

hive.metastore.http.client.bearer-token

Bearer token to use for authentication with the metastore service when HTTPS transport mode is used by using a https:// protocol in hive.metastore.uri. This must not be set with http://.

hive.metastore.http.client.additional-headers

Additional headers to send with metastore service requests. These headers must be comma-separated and delimited using :. For example, header1:value1,header2:value2 sends two headers header1 and header2 with the values as value1 and value2. Escape comma (,) or colon(:) characters in a header name or value with a backslash (\). Use X-Databricks-Unity-Catalog-Name=[catalog_name] to configure the required header values for Unity catalog.

Thrift metastore authentication#

In a Kerberized Hadoop cluster, Trino connects to the Hive metastore Thrift service using SASL and authenticates using Kerberos. Kerberos authentication for the metastore is configured in the connector’s properties file using the following optional properties:

Hive metastore Thrift service authentication properties#

Property value

Description

Default

hive.metastore.authentication.type

Hive metastore authentication type. One of NONE or KERBEROS. When using the default value of NONE, Kerberos authentication is disabled, and no other properties must be configured.

When set to KERBEROS the Hive connector connects to the Hive metastore Thrift service using SASL and authenticate using Kerberos.

NONE

hive.metastore.thrift.impersonation.enabled

Enable Hive metastore end user impersonation. See KERBEROS authentication with impersonation for more information.

false

hive.metastore.service.principal

The Kerberos principal of the Hive metastore service. The coordinator uses this to authenticate the Hive metastore.

The _HOST placeholder can be used in this property value. When connecting to the Hive metastore, the Hive connector substitutes in the hostname of the metastore server it is connecting to. This is useful if the metastore runs on multiple hosts.

Example: hive/[email protected] or hive/[email protected].

hive.metastore.client.principal

The Kerberos principal that Trino uses when connecting to the Hive metastore service.

Example: trino/[email protected] or trino/[email protected].

The _HOST placeholder can be used in this property value. When connecting to the Hive metastore, the Hive connector substitutes in the hostname of the worker node Trino is running on. This is useful if each worker node has its own Kerberos principal.

Unless KERBEROS authentication with impersonation is enabled, the principal specified by hive.metastore.client.principal must have sufficient privileges to remove files and directories within the hive/warehouse directory.

Warning: If the principal does have sufficient permissions, only the metadata is removed, and the data continues to consume disk space. This occurs because the Hive metastore is responsible for deleting the internal table data. When the metastore is configured to use Kerberos authentication, all of the HDFS operations performed by the metastore are impersonated. Errors deleting data are silently ignored.

hive.metastore.client.keytab

The path to the keytab file that contains a key for the principal specified by hive.metastore.client.principal. This file must be readable by the operating system user running Trino.

The following sections describe the configuration properties and values needed for the various authentication configurations needed to use the Hive metastore Thrift service with the Hive connector.

Default NONE authentication without impersonation#

hive.metastore.authentication.type=NONE

The default authentication type for the Hive metastore is NONE. When the authentication type is NONE, Trino connects to an unsecured Hive metastore. Kerberos is not used.

KERBEROS authentication with impersonation#

hive.metastore.authentication.type=KERBEROS
hive.metastore.thrift.impersonation.enabled=true
hive.metastore.service.principal=hive/[email protected]
[email protected]
hive.metastore.client.keytab=/etc/trino/hive.keytab

When the authentication type for the Hive metastore Thrift service is KERBEROS, Trino connects as the Kerberos principal specified by the property hive.metastore.client.principal. Trino authenticates this principal using the keytab specified by the hive.metastore.client.keytab property, and verifies that the identity of the metastore matches hive.metastore.service.principal.

When using KERBEROS Metastore authentication with impersonation, the principal specified by the hive.metastore.client.principal property must be allowed to impersonate the current Trino user, as discussed in the section Impersonation in Hadoop.

Keytab files must be distributed to every node in the Trino cluster.

Additional information about Keytab Files.

AWS Glue catalog configuration properties#

In order to use an AWS Glue catalog, you must configure your catalog file as follows:

hive.metastore=glue and provide further details with the following properties:

AWS Glue catalog configuration properties#

Property Name

Description

Default

hive.metastore.glue.region

AWS region of the Glue Catalog. This is required when not running in EC2, or when the catalog is in a different region. Example: us-east-1

hive.metastore.glue.endpoint-url

Glue API endpoint URL (optional). Example: https://glue.us-east-1.amazonaws.com

hive.metastore.glue.sts.region

AWS region of the STS service to authenticate with. This is required when running in a GovCloud region. Example: us-gov-east-1

hive.metastore.glue.proxy-api-id

The ID of the Glue Proxy API, when accessing Glue via an VPC endpoint in API Gateway.

hive.metastore.glue.sts.endpoint

STS endpoint URL to use when authenticating to Glue (optional). Example: https://sts.us-gov-east-1.amazonaws.com

hive.metastore.glue.pin-client-to-current-region

Pin Glue requests to the same region as the EC2 instance where Trino is running.

false

hive.metastore.glue.max-connections

Max number of concurrent connections to Glue.

30

hive.metastore.glue.max-error-retries

Maximum number of error retries for the Glue client.

10

hive.metastore.glue.default-warehouse-dir

Default warehouse directory for schemas created without an explicit location property.

hive.metastore.glue.aws-credentials-provider

Fully qualified name of the Java class to use for obtaining AWS credentials. Can be used to supply a custom credentials provider.

hive.metastore.glue.aws-access-key

AWS access key to use to connect to the Glue Catalog. If specified along with hive.metastore.glue.aws-secret-key, this parameter takes precedence over hive.metastore.glue.iam-role.

hive.metastore.glue.aws-secret-key

AWS secret key to use to connect to the Glue Catalog. If specified along with hive.metastore.glue.aws-access-key, this parameter takes precedence over hive.metastore.glue.iam-role.

hive.metastore.glue.catalogid

The ID of the Glue Catalog in which the metadata database resides.

hive.metastore.glue.iam-role

ARN of an IAM role to assume when connecting to the Glue Catalog.

hive.metastore.glue.external-id

External ID for the IAM role trust policy when connecting to the Glue Catalog.

hive.metastore.glue.partitions-segments

Number of segments for partitioned Glue tables.

5

hive.metastore.glue.get-partition-threads

Number of threads for parallel partition fetches from Glue.

20

hive.metastore.glue.read-statistics-threads

Number of threads for parallel statistic fetches from Glue.

5

hive.metastore.glue.write-statistics-threads

Number of threads for parallel statistic writes to Glue.

5

Iceberg-specific Glue catalog configuration properties#

When using the Glue catalog, the Iceberg connector supports the same general Glue configuration properties as previously described with the following additional property:

Iceberg Glue catalog configuration property#

Property name

Description

Default

iceberg.glue.skip-archive

Skip archiving an old table version when creating a new version in a commit. See AWS Glue Skip Archive.

true

Iceberg-specific metastores#

The Iceberg table format manages most metadata in metadata files in the object storage itself. A small amount of metadata, however, still requires the use of a metastore. In the Iceberg ecosystem, these smaller metastores are called Iceberg metadata catalogs, or just catalogs.

You can use a general metastore such as an HMS or AWS Glue, or you can use the Iceberg-specific REST, Nessie or JDBC metadata catalogs, as discussed in this section.

REST catalog#

In order to use the Iceberg REST catalog, configure the catalog type with iceberg.catalog.type=rest, and provide further details with the following properties:

Iceberg REST catalog configuration properties#

Property name

Description

iceberg.rest-catalog.uri

REST server API endpoint URI (required). Example: http://iceberg-with-rest:8181

iceberg.rest-catalog.warehouse

Warehouse identifier/location for the catalog (optional). Example: s3://my_bucket/warehouse_location

iceberg.rest-catalog.security

The type of security to use (default: NONE). OAUTH2 requires either a token or credential. Example: OAUTH2

iceberg.rest-catalog.session

Session information included when communicating with the REST Catalog. Options are NONE or USER (default: NONE).

iceberg.rest-catalog.oauth2.token

The bearer token used for interactions with the server. A token or credential is required for OAUTH2 security. Example: AbCdEf123456

iceberg.rest-catalog.oauth2.credential

The credential to exchange for a token in the OAuth2 client credentials flow with the server. A token or credential is required for OAUTH2 security. Example: AbCdEf123456

The following example shows a minimal catalog configuration using an Iceberg REST metadata catalog:

connector.name=iceberg
iceberg.catalog.type=rest
iceberg.rest-catalog.uri=http://iceberg-with-rest:8181

The REST catalog does not support view management or materialized view management.

JDBC catalog#

The Iceberg JDBC catalog is supported for the Iceberg connector. At a minimum, iceberg.jdbc-catalog.driver-class, iceberg.jdbc-catalog.connection-url and iceberg.jdbc-catalog.catalog-name must be configured. When using any database besides PostgreSQL, a JDBC driver jar file must be placed in the plugin directory.

Warning

The JDBC catalog may have compatibility issues if Iceberg introduces breaking changes in the future. Consider the REST catalog as an alternative solution.

The JDBC catalog requires the metadata tables to already exist. Refer to Iceberg repository for creating those tables.

At a minimum, iceberg.jdbc-catalog.driver-class, iceberg.jdbc-catalog.connection-url, and iceberg.jdbc-catalog.catalog-name must be configured. When using any database besides PostgreSQL, a JDBC driver jar file must be placed in the plugin directory. The following example shows a minimal catalog configuration using an Iceberg REST metadata catalog:

connector.name=iceberg
iceberg.catalog.type=jdbc
iceberg.jdbc-catalog.catalog-name=test
iceberg.jdbc-catalog.driver-class=org.postgresql.Driver
iceberg.jdbc-catalog.connection-url=jdbc:postgresql://example.net:5432/database
iceberg.jdbc-catalog.connection-user=admin
iceberg.jdbc-catalog.connection-password=test
iceberg.jdbc-catalog.default-warehouse-dir=s3://bucket

The JDBC catalog does not support view management or materialized view management.

Nessie catalog#

In order to use a Nessie catalog, configure the catalog type with iceberg.catalog.type=nessie and provide further details with the following properties:

Nessie catalog configuration properties#

Property name

Description

iceberg.nessie-catalog.uri

Nessie API endpoint URI (required). Example: https://localhost:19120/api/v1

iceberg.nessie-catalog.ref

The branch/tag to use for Nessie. Defaults to main.

iceberg.nessie-catalog.default-warehouse-dir

Default warehouse directory for schemas created without an explicit location property. Example: /tmp

iceberg.nessie-catalog.read-timeout

The read timeout duration for requests to the Nessie server. Defaults to 25s.

iceberg.nessie-catalog.connection-timeout

The connection timeout duration for connection requests to the Nessie server. Defaults to 5s.

iceberg.nessie-catalog.enable-compression

Configure whether compression should be enabled or not for requests to the Nessie server. Defaults to true.

iceberg.nessie-catalog.authentication.type

The authentication type to use. Available value is BEARER. Defaults to no authentication.

iceberg.nessie-catalog.authentication.token

The token to use with BEARER authentication. Example: SXVLUXUhIExFQ0tFUiEK

connector.name=iceberg
iceberg.catalog.type=nessie
iceberg.nessie-catalog.uri=https://localhost:19120/api/v1
iceberg.nessie-catalog.default-warehouse-dir=/tmp

The Nessie catalog does not support view management or materialized view management.

Access tables with Athena partition projection metadata#

Partition projection is a feature of AWS Athena often used to speed up query processing with highly partitioned tables when using the Hive connector.

Trino supports partition projection table properties stored in the Hive metastore or Glue catalog, and it reimplements this functionality. Currently, there is a limitation in comparison to AWS Athena for date projection, as it only supports intervals of DAYS, HOURS, MINUTES, and SECONDS.

If there are any compatibility issues blocking access to a requested table when partition projection is enabled, set the partition_projection_ignore table property to true for a table to bypass any errors.

Refer to Table properties and Column properties for configuration of partition projection.

Configure metastore for Avro#

For catalogs using the Hive connector, you must add the following property definition to the Hive metastore configuration file hive-site.xml and restart the metastore service to enable first-class support for Avro tables when using Hive 3.x:

<property>
     <!-- https://community.hortonworks.com/content/supportkb/247055/errorjavalangunsupportedoperationexception-storage.html -->
     <name>metastore.storage.schema.reader.impl</name>
     <value>org.apache.hadoop.hive.metastore.SerDeStorageSchemaReader</value>
 </property>