Hive коннектор

Примечание

Ниже приведена оригинальная документация Trino. Скоро мы ее переведем на русский язык и дополним полезными примерами.

The Hive connector allows querying data stored in an Apache Hive data warehouse. Hive is a combination of three components:

• Data files in varying formats, that are typically stored in the Hadoop Distributed File System (HDFS) or in object storage systems such as Amazon S3.

• Metadata about how the data files are mapped to schemas and tables. This metadata is stored in a database, such as MySQL, and is accessed via the Hive metastore service.

• A query language called HiveQL. This query language is executed on a distributed computing framework such as MapReduce or Tez.

Trino only uses the first two components: the data and the metadata. It does not use HiveQL or any part of Hive’s execution environment.

Requirements

The Hive connector requires a Hive metastore service (HMS), or a compatible implementation of the Hive metastore, such as AWS Glue.

You must select and configure a supported file system in your catalog configuration file.

The coordinator and all workers must have network access to the Hive metastore and the storage system. Hive metastore access with the Thrift protocol defaults to using port 9083.

Data files must be in a supported file format. File formats can be configured using the format table property and other specific properties:

• ORC

• Parquet

• Avro

In the case of serializable formats, only specific SerDes are allowed:

• RCText - RCFile using ColumnarSerDe

• RCBinary - RCFile using LazyBinaryColumnarSerDe

• SequenceFile

• CSV - using org.apache.hadoop.hive.serde2.OpenCSVSerde

• JSON - using org.apache.hive.hcatalog.data.JsonSerDe

• OPENX_JSON - OpenX JSON SerDe from org.openx.data.jsonserde.JsonSerDe. Find more details about the Trino implementation in the source repository.

• TextFile

General configuration

To configure the Hive connector, create a catalog properties file etc/catalog/example.properties that references the hive connector.

You must configure a metastore for metadata.

You must select and configure one of the supported file systems.

connector.name=hive
hive.metastore.uri=thrift://example.net:9083
fs.x.enabled=true

Replace the fs.x.enabled configuration property with the desired file system.

If you are using AWS Glue as your metastore, you must instead set hive.metastore to glue:

connector.name=hive
hive.metastore=glue

Each metastore type has specific configuration properties along with General metastore configuration properties.

Multiple Hive clusters

You can have as many catalogs as you need, so if you have additional Hive clusters, simply add another properties file to etc/catalog with a different name, making sure it ends in .properties. For example, if you name the property file sales.properties, Trino creates a catalog named sales using the configured connector.

Hive general configuration properties

The following table lists general configuration properties for the Hive connector. There are additional sets of configuration properties throughout the Hive connector documentation.

Hive general configuration properties

Property Name	Description	Default
hive.recursive-directories	Enable reading data from subdirectories of table or partition locations. If disabled, subdirectories are ignored. This is equivalent to the hive.mapred.supports.subdirectories property in Hive.	false
hive.ignore-absent-partitions	Ignore partitions when the file system location does not exist rather than failing the query. This skips data that may be expected to be part of the table.	false
hive.storage-format	The default file format used when creating new tables.	ORC
hive.orc.use-column-names	Access ORC columns by name. By default, columns in ORC files are accessed by their ordinal position in the Hive table definition. The equivalent catalog session property is orc_use_column_names. See also, ORC format configuration properties	false
hive.parquet.use-column-names	Access Parquet columns by name by default. Set this property to false to access columns by their ordinal position in the Hive table definition. The equivalent catalog session property is parquet_use_column_names. See also, Parquet format configuration properties	true
hive.parquet.time-zone	Time zone for Parquet read and write.	JVM default
hive.compression-codec	The compression codec to use when writing files. Possible values are NONE, SNAPPY, LZ4, ZSTD, or GZIP.	GZIP
hive.force-local-scheduling	Force splits to be scheduled on the same node as the Hadoop DataNode process serving the split data. This is useful for installations where Trino is collocated with every DataNode.	false
hive.respect-table-format	Should new partitions be written using the existing table format or the default Trino format?	true
hive.immutable-partitions	Can new data be inserted into existing partitions? If true then setting hive.insert-existing-partitions-behavior to APPEND is not allowed. This also affects the insert_existing_partitions_behavior session property in the same way.	false
hive.insert-existing-partitions-behavior	What happens when data is inserted into an existing partition? Possible values are APPEND - appends data to existing partitions OVERWRITE - overwrites existing partitions ERROR - modifying existing partitions is not allowed The equivalent catalog session property is insert_existing_partitions_behavior.	APPEND
hive.target-max-file-size	Best effort maximum size of new files.	1GB
hive.create-empty-bucket-files	Should empty files be created for buckets that have no data?	false
hive.validate-bucketing	Enables validation that data is in the correct bucket when reading bucketed tables.	true
hive.partition-statistics-sample-size	Specifies the number of partitions to analyze when computing table statistics.	100
hive.max-partitions-per-writers	Maximum number of partitions per writer.	100
hive.max-partitions-for-eager-load	The maximum number of partitions for a single table scan to load eagerly on the coordinator. Certain optimizations are not possible without eager loading.	100,000
hive.max-partitions-per-scan	Maximum number of partitions for a single table scan.	1,000,000
hive.non-managed-table-writes-enabled	Enable writes to non-managed (external) Hive tables.	false
hive.non-managed-table-creates-enabled	Enable creating non-managed (external) Hive tables.	true
hive.collect-column-statistics-on-write	Enables automatic column level statistics collection on write. See Table statistics for details.	true
hive.file-status-cache-tables	Cache directory listing for specific tables. Examples: fruit.apple,fruit.orange to cache listings only for tables apple and orange in schema fruit fruit.*,vegetable.* to cache listings for all tables in schemas fruit and vegetable * to cache listings for all tables in all schemas
hive.file-status-cache.max-retained-size	Maximum retained size of cached file status entries.	1GB
hive.file-status-cache-expire-time	How long a cached directory listing is considered valid.	1m
hive.per-transaction-file-status-cache.max-retained-size	Maximum retained size of all entries in per transaction file status cache. Retained size limit is shared across all running queries.	100MB
hive.rcfile.time-zone	Adjusts binary encoded timestamp values to a specific time zone. For Hive 3.1+, this must be set to UTC.	JVM default
hive.timestamp-precision	Specifies the precision to use for Hive columns of type TIMESTAMP. Possible values are MILLISECONDS, MICROSECONDS and NANOSECONDS. Values with higher precision than configured are rounded. The equivalent catalog session property is timestamp_precision for session specific use.	MILLISECONDS
hive.temporary-staging-directory-enabled	Controls whether the temporary staging directory configured at hive.temporary-staging-directory-path is used for write operations. Temporary staging directory is never used for writes to non-sorted tables on S3, encrypted HDFS or external location. Writes to sorted tables will utilize this path for staging temporary files during sorting operation. When disabled, the target storage will be used for staging while writing sorted tables which can be inefficient when writing to object stores like S3.	true
hive.temporary-staging-directory-path	Controls the location of temporary staging directory that is used for write operations. The ${USER} placeholder can be used to use a different location for each user.	/tmp/presto-${USER}
hive.hive-views.enabled	Enable translation for Hive views.	false
hive.hive-views.legacy-translation	Use the legacy algorithm to translate Hive views. You can use the hive_views_legacy_translation catalog session property for temporary, catalog specific use.	false
hive.parallel-partitioned-bucketed-writes	Improve parallelism of partitioned and bucketed table writes. When disabled, the number of writing threads is limited to number of buckets.	true
hive.query-partition-filter-required	Set to true to force a query to use a partition filter. You can use the query_partition_filter_required catalog session property for temporary, catalog specific use.	false
hive.query-partition-filter-required-schemas	Allow specifying the list of schemas for which Trino will enforce that queries use a filter on partition keys for source tables. The list can be specified using the hive.query-partition-filter-required-schemas, or the query_partition_filter_required_schemas session property. The list is taken into consideration only if the hive.query-partition-filter-required configuration property or the query_partition_filter_required session property is set to true.	[]
hive.table-statistics-enabled	Enables Table statistics. The equivalent catalog session property is statistics_enabled for session specific use. Set to false to disable statistics. Disabling statistics means that Cost-based оптимизация can not make smart decisions about the query plan.	true
hive.auto-purge	Set the default value for the auto_purge table property for managed tables. See the Table properties for more information on auto_purge.	false
hive.partition-projection-enabled	Enables Athena partition projection support	false
hive.max-partition-drops-per-query	Maximum number of partitions to drop in a single query.	100,000
hive.single-statement-writes	Enables auto-commit for all writes. This can be used to disallow multi-statement write transactions.	false

File system access configuration

The connector supports accessing the following file systems:

• Azure Storage file system support

• Google Cloud Storage file system support

• S3 file system support

• HDFS file system support

You must enable and configure the specific file system access. Legacy support is not recommended and will be removed.

Fault-tolerant execution support

The connector supports Fault-tolerant execution of query processing. Read and write operations are both supported with any retry policy on non-transactional tables.

Read operations are supported with any retry policy on transactional tables. Write operations and CREATE TABLE ... AS operations are not supported with any retry policy on transactional tables.

Security

The connector supports different means of authentication for the used file system and metastore.

In addition, the following security-related features are supported.

Authorization

You can enable authorization checks by setting the hive.security property in the catalog properties file. This property must be one of the following values:

hive.security property values

Property value	Description
allow-all (default value)	No authorization checks are enforced.
read-only	Operations that read data or metadata, such as SELECT, are permitted, but none of the operations that write data or metadata, such as CREATE, INSERT or DELETE, are allowed.
file	Authorization checks are enforced using a catalog-level access control configuration file whose path is specified in the security.config-file catalog configuration property. See Catalog-level access control files for details.
sql-standard	Users are permitted to perform the operations as long as they have the required privileges as per the SQL standard. In this mode, Trino enforces the authorization checks for queries based on the privileges defined in Hive metastore. To alter these privileges, use the GRANT privilege and REVOKE privilege commands. See the SQL standard based authorization section for details.

SQL standard based authorization

When sql-standard security is enabled, Trino enforces the same SQL standard-based authorization as Hive does.

Since Trino’s ROLE syntax support matches the SQL standard, and Hive does not exactly follow the SQL standard, there are the following limitations and differences:

• CREATE ROLE role WITH ADMIN is not supported.

• The admin role must be enabled to execute CREATE ROLE, DROP ROLE or CREATE SCHEMA.

• GRANT role TO user GRANTED BY someone is not supported.

• REVOKE role FROM user GRANTED BY someone is not supported.

• By default, all a user’s roles, except admin, are enabled in a new user session.

• One particular role can be selected by executing SET ROLE role.

• SET ROLE ALL enables all of a user’s roles except admin.

• The admin role must be enabled explicitly by executing SET ROLE admin.

• GRANT privilege ON SCHEMA schema is not supported. Schema ownership can be changed with ALTER SCHEMA schema SET AUTHORIZATION user

SQL support

The connector provides read access and write access to data and metadata in the configured object storage system and metadata stores:

• Globally available statements; see also Globally available statements

• Read operations

• Изменение данных:

  • DML; see also Hive-specific data management

  • Схемы и таблицы; see also Hive-specific schema and table management

  • Представления (view); see also Hive-specific view management

• Функции (routine)

• Безопасность: see also SQL standard-based authorization for object storage

• Транзакции

Refer to the migration guide for practical advice on migrating from Hive to Trino.

The following sections provide Hive-specific information regarding SQL support.

Basic usage examples

The examples shown here work on Google Cloud Storage by replacing s3:// with gs://.

Create a new Hive table named page_views in the web schema that is stored using the ORC file format, partitioned by date and country, and bucketed by user into 50 buckets. Note that Hive requires the partition columns to be the last columns in the table:

CREATE TABLE example.web.page_views (
  view_time TIMESTAMP,
  user_id BIGINT,
  page_url VARCHAR,
  ds DATE,
  country VARCHAR
)
WITH (
  format = 'ORC',
  partitioned_by = ARRAY['ds', 'country'],
  bucketed_by = ARRAY['user_id'],
  bucket_count = 50
)

Create a new Hive schema named web that stores tables in an S3 bucket named my-bucket:

CREATE SCHEMA example.web
WITH (location = 's3://my-bucket/')

Drop a schema:

DROP SCHEMA example.web

Drop a partition from the page_views table:

DELETE FROM example.web.page_views
WHERE ds = DATE '2016-08-09'
  AND country = 'US'

Query the page_views table:

SELECT * FROM example.web.page_views

List the partitions of the page_views table:

SELECT * FROM example.web."page_views$partitions"

Create an external Hive table named request_logs that points at existing data in S3:

CREATE TABLE example.web.request_logs (
  request_time TIMESTAMP,
  url VARCHAR,
  ip VARCHAR,
  user_agent VARCHAR
)
WITH (
  format = 'TEXTFILE',
  external_location = 's3://my-bucket/data/logs/'
)

Collect statistics for the request_logs table:

ANALYZE example.web.request_logs;

Drop the external table request_logs. This only drops the metadata for the table. The referenced data directory is not deleted:

DROP TABLE example.web.request_logs

• CREATE TABLE AS can be used to create transactional tables in ORC format like this:

  CREATE TABLE <name>
  WITH (
      format='ORC',
      transactional=true
  )
  AS <query>
  

Add an empty partition to the page_views table:

CALL system.create_empty_partition(
    schema_name => 'web',
    table_name => 'page_views',
    partition_columns => ARRAY['ds', 'country'],
    partition_values => ARRAY['2016-08-09', 'US']);

Drop stats for a partition of the page_views table:

CALL system.drop_stats(
    schema_name => 'web',
    table_name => 'page_views',
    partition_values => ARRAY[ARRAY['2016-08-09', 'US']]);

Procedures

Use the CALL statement to perform data manipulation or administrative tasks. Procedures must include a qualified catalog name, if your Hive catalog is called web:

CALL web.system.example_procedure()

The following procedures are available:

• system.create_empty_partition(schema_name, table_name, partition_columns, partition_values)

  Create an empty partition in the specified table.

• system.sync_partition_metadata(schema_name, table_name, mode, case_sensitive)

  Check and update partitions list in metastore. There are three modes available:

  • ADD : add any partitions that exist on the file system, but not in the metastore.

  • DROP: drop any partitions that exist in the metastore, but not on the file system.

  • FULL: perform both ADD and DROP.

  The case_sensitive argument is optional. The default value is true for compatibility with Hive’s MSCK REPAIR TABLE behavior, which expects the partition column names in file system paths to use lowercase (e.g. col_x=SomeValue). Partitions on the file system not conforming to this convention are ignored, unless the argument is set to false.

• system.drop_stats(schema_name, table_name, partition_values)

  Drops statistics for a subset of partitions or the entire table. The partitions are specified as an array whose elements are arrays of partition values (similar to the partition_values argument in create_empty_partition). If partition_values argument is omitted, stats are dropped for the entire table.

• system.register_partition(schema_name, table_name, partition_columns, partition_values, location)

  Registers existing location as a new partition in the metastore for the specified table.

  When the location argument is omitted, the partition location is constructed using partition_columns and partition_values.

  Due to security reasons, the procedure is enabled only when hive.allow-register-partition-procedure is set to true.

• system.unregister_partition(schema_name, table_name, partition_columns, partition_values)

  Unregisters given, existing partition in the metastore for the specified table. The partition data is not deleted.

• system.flush_metadata_cache()

  Flush all Hive metadata caches.

• system.flush_metadata_cache(schema_name => ..., table_name => ...)

  Flush Hive metadata caches entries connected with selected table. Procedure requires named parameters to be passed

• system.flush_metadata_cache(schema_name => ..., table_name => ..., partition_columns => ARRAY[...], partition_values => ARRAY[...])

  Flush Hive metadata cache entries connected with selected partition. Procedure requires named parameters to be passed.

Data management

The DML functionality includes support for INSERT, UPDATE, DELETE, and MERGE statements, with the exact support depending on the storage system, file format, and metastore.

When connecting to a Hive metastore version 3.x, the Hive connector supports reading from and writing to insert-only and ACID tables, with full support for partitioning and bucketing.

DELETE applied to non-transactional tables is only supported if the table is partitioned and the WHERE clause matches entire partitions. Transactional Hive tables with ORC format support «row-by-row» deletion, in which the WHERE clause may match arbitrary sets of rows.

UPDATE is only supported for transactional Hive tables with format ORC. UPDATE of partition or bucket columns is not supported.

MERGE is only supported for ACID tables.

ACID tables created with Hive Streaming Ingest are not supported.

Schema and table management

The Hive connector supports querying and manipulating Hive tables and schemas (databases). While some uncommon operations must be performed using Hive directly, most operations can be performed using Trino.

Schema evolution

Hive table partitions can differ from the current table schema. This occurs when the data types of columns of a table are changed from the data types of columns of preexisting partitions. The Hive connector supports this schema evolution by allowing the same conversions as Hive. The following table lists possible data type conversions.

Hive schema evolution type conversion

Data type	Converted to
BOOLEAN	VARCHAR
VARCHAR	BOOLEAN, TINYINT, SMALLINT, INTEGER, BIGINT, REAL, DOUBLE, TIMESTAMP, DATE, CHAR as well as narrowing conversions for VARCHAR
CHAR	VARCHAR, narrowing conversions for CHAR
TINYINT	VARCHAR, SMALLINT, INTEGER, BIGINT, DOUBLE, DECIMAL
SMALLINT	VARCHAR, INTEGER, BIGINT, DOUBLE, DECIMAL
INTEGER	VARCHAR, BIGINT, DOUBLE, DECIMAL
BIGINT	VARCHAR, DOUBLE, DECIMAL
REAL	DOUBLE, DECIMAL
DOUBLE	FLOAT, DECIMAL
DECIMAL	DOUBLE, REAL, VARCHAR, TINYINT, SMALLINT, INTEGER, BIGINT, as well as narrowing and widening conversions for DECIMAL
DATE	VARCHAR
TIMESTAMP	VARCHAR, DATE
VARBINARY	VARCHAR

Any conversion failure results in null, which is the same behavior as Hive. For example, converting the string 'foo' to a number, or converting the string '1234' to a TINYINT (which has a maximum value of 127).

Avro schema evolution

Trino supports querying and manipulating Hive tables with the Avro storage format, which has the schema set based on an Avro schema file/literal. Trino is also capable of creating the tables in Trino by infering the schema from a valid Avro schema file located locally, or remotely in HDFS/Web server.

To specify that the Avro schema should be used for interpreting table data, use the avro_schema_url table property.

The schema can be placed in the local file system or remotely in the following locations:

• HDFS (e.g. avro_schema_url = 'hdfs://user/avro/schema/avro_data.avsc')

• S3 (e.g. avro_schema_url = 's3n:///schema_bucket/schema/avro_data.avsc')

• A web server (e.g. avro_schema_url = 'http://example.org/schema/avro_data.avsc')

The URL, where the schema is located, must be accessible from the Hive metastore and Trino coordinator/worker nodes.

Alternatively, you can use the table property avro_schema_literal to define the Avro schema.

The table created in Trino using the avro_schema_url or avro_schema_literal property behaves the same way as a Hive table with avro.schema.url or avro.schema.literal set.

Example:

CREATE TABLE example.avro.avro_data (
   id BIGINT
 )
WITH (
   format = 'AVRO',
   avro_schema_url = '/usr/local/avro_data.avsc'
)

The columns listed in the DDL (id in the above example) is ignored if avro_schema_url is specified. The table schema matches the schema in the Avro schema file. Before any read operation, the Avro schema is accessed so the query result reflects any changes in schema. Thus Trino takes advantage of Avro’s backward compatibility abilities.

If the schema of the table changes in the Avro schema file, the new schema can still be used to read old data. Newly added/renamed fields must have a default value in the Avro schema file.

The schema evolution behavior is as follows:

• Column added in new schema: Data created with an older schema produces a default value when table is using the new schema.

• Column removed in new schema: Data created with an older schema no longer outputs the data from the column that was removed.

• Column is renamed in the new schema: This is equivalent to removing the column and adding a new one, and data created with an older schema produces a default value when table is using the new schema.

• Changing type of column in the new schema: If the type coercion is supported by Avro or the Hive connector, then the conversion happens. An error is thrown for incompatible types.

Limitations

The following operations are not supported when avro_schema_url is set:

• CREATE TABLE AS is not supported.

• Bucketing(bucketed_by) columns are not supported in CREATE TABLE.

• ALTER TABLE commands modifying columns are not supported.

ALTER TABLE EXECUTE

The connector supports the following commands for use with ALTER TABLE EXECUTE.

optimize

The optimize command is used for rewriting the content of the specified table so that it is merged into fewer but larger files. If the table is partitioned, the data compaction acts separately on each partition selected for optimization. This operation improves read performance.

All files with a size below the optional file_size_threshold parameter (default value for the threshold is 100MB) are merged:

ALTER TABLE test_table EXECUTE optimize

The following statement merges files in a table that are under 128 megabytes in size:

ALTER TABLE test_table EXECUTE optimize(file_size_threshold => '128MB')

You can use a WHERE clause with the columns used to partition the table to filter which partitions are optimized:

ALTER TABLE test_partitioned_table EXECUTE optimize
WHERE partition_key = 1

You can use a more complex WHERE clause to narrow down the scope of the optimize procedure. The following example casts the timestamp values to dates, and uses a comparison to only optimize partitions with data from the year 2022 or newer:

ALTER TABLE test_table EXECUTE optimize
WHERE CAST(timestamp_tz AS DATE) > DATE '2021-12-31'

The optimize command is disabled by default, and can be enabled for a catalog with the <catalog-name>.non_transactional_optimize_enabled session property:

SET SESSION <catalog_name>.non_transactional_optimize_enabled=true

Предупреждение

Because Hive tables are non-transactional, take note of the following possible outcomes:

• If queries are run against tables that are currently being optimized, duplicate rows may be read.

• In rare cases where exceptions occur during the optimize operation, a manual cleanup of the table directory is needed. In this situation, refer to the Trino logs and query failure messages to see which files must be deleted.

Table properties

Table properties supply or set metadata for the underlying tables. This is key for CREATE TABLE AS statements. Table properties are passed to the connector using a WITH clause:

CREATE TABLE tablename
WITH (format='CSV',
      csv_escape = '"')

Hive connector table properties

Property name	Description	Default
auto_purge	Indicates to the configured metastore to perform a purge when a table or partition is deleted instead of a soft deletion using the trash.
avro_schema_url	The URI pointing to Avro schema evolution for the table.
bucket_count	The number of buckets to group data into. Only valid if used with bucketed_by.	0
bucketed_by	The bucketing column for the storage table. Only valid if used with bucket_count.	[]
bucketing_version	Specifies which Hive bucketing version to use. Valid values are 1 or 2.
csv_escape	The CSV escape character. Requires CSV format.
csv_quote	The CSV quote character. Requires CSV format.
csv_separator	The CSV separator character. Requires CSV format. You can use other separators such as | or use Unicode to configure invisible separators such tabs with U&'\0009'.	,
external_location	The URI for an external Hive table on S3, Azure Blob Storage, etc. See the Basic usage examples for more information.
format	The table file format. Valid values include ORC, PARQUET, AVRO, RCBINARY, RCTEXT, SEQUENCEFILE, JSON, OPENX_JSON, TEXTFILE, CSV, and REGEX. The catalog property hive.storage-format sets the default value and can change it to a different default.
null_format	The serialization format for NULL value. Requires TextFile, RCText, or SequenceFile format.
orc_bloom_filter_columns	Comma separated list of columns to use for ORC bloom filter. It improves the performance of queries using equality predicates, such as =, IN and small range predicates, when reading ORC files. Requires ORC format.	[]
orc_bloom_filter_fpp	The ORC bloom filters false positive probability. Requires ORC format.	0.05
partitioned_by	The partitioning column for the storage table. The columns listed in the partitioned_by clause must be the last columns as defined in the DDL.	[]
parquet_bloom_filter_columns	Comma separated list of columns to use for Parquet bloom filter. It improves the performance of queries using equality predicates, such as =, IN and small range predicates, when reading Parquet files. Requires Parquet format.	[]
skip_footer_line_count	The number of footer lines to ignore when parsing the file for data. Requires TextFile or CSV format tables.
skip_header_line_count	The number of header lines to ignore when parsing the file for data. Requires TextFile or CSV format tables.
sorted_by	The column to sort by to determine bucketing for row. Only valid if bucketed_by and bucket_count are specified as well.	[]
textfile_field_separator	Allows the use of custom field separators, such as „|“, for TextFile formatted tables.
textfile_field_separator_escape	Allows the use of a custom escape character for TextFile formatted tables.
transactional	Set this property to true to create an ORC ACID transactional table. Requires ORC format. This property may be shown as true for insert-only tables created using older versions of Hive.
partition_projection_enabled	Enables partition projection for selected table. Mapped from AWS Athena table property projection.enabled.
partition_projection_ignore	Ignore any partition projection properties stored in the metastore for the selected table. This is a Trino-only property which allows you to work around compatibility issues on a specific table, and if enabled, Trino ignores all other configuration options related to partition projection.
partition_projection_location_template	Projected partition location template, such as s3a://test/name=${name}/. Mapped from the AWS Athena table property storage.location.template	${table_location}/${partition_name}
extra_properties	Additional properties added to a Hive table. The properties are not used by Trino, and are available in the $properties metadata table. The properties are not included in the output of SHOW CREATE TABLE statements.

Metadata tables

The raw Hive table properties are available as a hidden table, containing a separate column per table property, with a single row containing the property values.

$properties table

The properties table name is composed with the table name and $properties appended. It exposes the parameters of the table in the metastore.

You can inspect the property names and values with a simple query:

SELECT * FROM example.web."page_views$properties";

       stats_generated_via_stats_task        | auto.purge |       trino_query_id       | trino_version | transactional
---------------------------------------------+------------+-----------------------------+---------------+---------------
 workaround for potential lack of HIVE-12730 | false      | 20230705_152456_00001_nfugi | 434           | false

$partitions table

The $partitions table provides a list of all partition values of a partitioned table.

The following example query returns all partition values from the page_views table in the web schema of the example catalog:

SELECT * FROM example.web."page_views$partitions";

     day    | country
------------+---------
 2023-07-01 | POL
 2023-07-02 | POL
 2023-07-03 | POL
 2023-03-01 | USA
 2023-03-02 | USA

Column properties

Hive connector column properties

Property name	Description	Default
partition_projection_type	Defines the type of partition projection to use on this column. May be used only on partition columns. Available types: ENUM, INTEGER, DATE, INJECTED. Mapped from the AWS Athena table property projection.${columnName}.type.
partition_projection_values	Used with partition_projection_type set to ENUM. Contains a static list of values used to generate partitions. Mapped from the AWS Athena table property projection.${columnName}.values.
partition_projection_range	Used with partition_projection_type set to INTEGER or DATE to define a range. It is a two-element array, describing the minimum and maximum range values used to generate partitions. Generation starts from the minimum, then increments by the defined partition_projection_interval to the maximum. For example, the format is ['1', '4'] for a partition_projection_type of INTEGER and ['2001-01-01', '2001-01-07'] or ['NOW-3DAYS', 'NOW'] for a partition_projection_type of DATE. Mapped from the AWS Athena table property projection.${columnName}.range.
partition_projection_interval	Used with partition_projection_type set to INTEGER or DATE. It represents the interval used to generate partitions within the given range partition_projection_range. Mapped from the AWS Athena table property projection.${columnName}.interval.
partition_projection_digits	Used with partition_projection_type set to INTEGER. The number of digits to be used with integer column projection. Mapped from the AWS Athena table property projection.${columnName}.digits.
partition_projection_format	Used with partition_projection_type set to DATE. The date column projection format, defined as a string such as yyyy MM or MM-dd-yy HH:mm:ss for use with the Java DateTimeFormatter class. Mapped from the AWS Athena table property projection.${columnName}.format.
partition_projection_interval_unit	Used with partition_projection_type=DATA. The date column projection range interval unit given in partition_projection_interval. Mapped from the AWS Athena table property projection.${columnName}.interval.unit.

Metadata columns

In addition to the defined columns, the Hive connector automatically exposes metadata in a number of hidden columns in each table:

• $bucket: Bucket number for this row

• $path: Full file system path name of the file for this row

• $file_modified_time: Date and time of the last modification of the file for this row

• $file_size: Size of the file for this row

• $partition: Partition name for this row

You can use these columns in your SQL statements like any other column. They can be selected directly, or used in conditional statements. For example, you can inspect the file size, location and partition for each record:

SELECT *, "$path", "$file_size", "$partition"
FROM example.web.page_views;

Retrieve all records that belong to files stored in the partition ds=2016-08-09/country=US:

SELECT *, "$path", "$file_size"
FROM example.web.page_views
WHERE "$partition" = 'ds=2016-08-09/country=US'

View management

Trino allows reading from Hive materialized views, and can be configured to support reading Hive views.

Materialized views

The Hive connector supports reading from Hive materialized views. In Trino, these views are presented as regular, read-only tables.

Hive views

Hive views are defined in HiveQL and stored in the Hive Metastore Service. They are analyzed to allow read access to the data.

The Hive connector includes support for reading Hive views with three different modes.

• Disabled

• Legacy

• Experimental

If using Hive views from Trino is required, you must compare results in Hive and Trino for each view definition to ensure identical results. Use the experimental mode whenever possible. Avoid using the legacy mode. Leave Hive views support disabled, if you are not accessing any Hive views from Trino.

You can configure the behavior in your catalog properties file.

By default, Hive views are executed with the RUN AS DEFINER security mode. Set the hive.hive-views.run-as-invoker catalog configuration property to true to use RUN AS INVOKER semantics.

Disabled

The default behavior is to ignore Hive views. This means that your business logic and data encoded in the views is not available in Trino.

Legacy

A very simple implementation to execute Hive views, and therefore allow read access to the data in Trino, can be enabled with hive.hive-views.enabled=true and hive.hive-views.legacy-translation=true.

For temporary usage of the legacy behavior for a specific catalog, you can set the hive_views_legacy_translation catalog session property to true.

This legacy behavior interprets any HiveQL query that defines a view as if it is written in SQL. It does not do any translation, but instead relies on the fact that HiveQL is very similar to SQL.

This works for very simple Hive views, but can lead to problems for more complex queries. For example, if a HiveQL function has an identical signature but different behaviors to the SQL version, the returned results may differ. In more extreme cases the queries might fail, or not even be able to be parsed and executed.

Experimental

The new behavior is better engineered and has the potential to become a lot more powerful than the legacy implementation. It can analyze, process, and rewrite Hive views and contained expressions and statements.

It supports the following Hive view functionality:

• UNION [DISTINCT] and UNION ALL against Hive views

• Nested GROUP BY clauses

• current_user()

• LATERAL VIEW OUTER EXPLODE

• LATERAL VIEW [OUTER] EXPLODE on array of struct

• LATERAL VIEW json_tuple

You can enable the experimental behavior with hive.hive-views.enabled=true. Remove the hive.hive-views.legacy-translation property or set it to false to make sure legacy is not enabled.

Keep in mind that numerous features are not yet implemented when experimenting with this feature. The following is an incomplete list of missing functionality:

• HiveQL current_date, current_timestamp, and others

• Hive function calls including translate(), window functions, and others

• Common table expressions and simple case expressions

• Honor timestamp precision setting

• Support all Hive data types and correct mapping to Trino types

• Ability to process custom UDFs

Производительность

Данная секция описывает важные улучшения производительности, реализованные в Hive коннекторе.

Локальный дисковый кэш данных

Коннектор позволяет сохранять часть данных из озера данных на дисках worker-узлов CedrusData для ускорения доступа к ним. Во многих случаях использование локального дискового кэша приводит к кратному ускорению запросов.

При каждом доступе к колонке CedrusData проверяет, были ли закэшированные данные изменены в удаленном источнике. Если обнаружено изменение, локальные данные будут удалены и закэшированы повторно.

CedrusData кэширует метаданные файлов, а также диапазоны записей по мере необходимости. Гранулярность кэширования диапазонов записей зависит от формата:

• Для формата Parquet единицей кэширования являются данные колонки внутри row group

• Для формата ORC единицей кэширования являются данные колонки внутри stripe

Для включения локального дискового кэша необходимо:

• Установить параметр конфигурации каталога cedrusdata.hive.data-cache.enabled=true

• Указать путь к файлу, в котором описаны правила кэширования в JSON формате

• Для узлов, которые будут выполнять запросы (все worker-узлы, а также coordinator-узел, запущенный с параметром node-scheduler.include-coordinator=true) необходимо также указать путь к директории, в которой CedrusData будет хранить закэшированные данные. Параметр конфигурации: cedrusdata.hive.data-cache.path

Пример конфигурации для координатора, который не выполняет запросы:

cedrusdata.hive.data-cache.enabled=true
cedrusdata.hive.data-cache.rules.file=/path/to/rules.json

Пример конфигурации для worker-узла или координатора, который выполняет запросы (node-scheduler.include-coordinator=true):

cedrusdata.hive.data-cache.enabled=true
cedrusdata.hive.data-cache.rules.file=/path/to/rules.json
cedrusdata.hive.data-cache.path=file:///path/to/cache/dir

Правила кэширования необходимо задать в отдельном файле в формате:

{
  "rules": [
    <rule1>,
    <rule2>,
    ...
  ]
}

Где <rule> представляет собой отдельное правило в формате:

{
  "schema": "<regexp схемы>",
  "table": "<regexp таблицы>",
  "partition_filter": "<предикат ключа партиционирования таблицы>",
  "distribution_mode": "<способ распределения сплитов по узлам>",
  "affinity_mode": "<способ привязки сплитов к узлам>",
  "affinity_node_count": "<количество узлов на которых может быть обработан сплит>",
  "disable_cache": <флаг отключения кэширования>
}

Подробное описание полей правила:

Название	Описание
schema	Обязательное поле. Задает паттерн для схем в формате Java Pattern. Например, .* соответствует всем схемам, s1 соответствует схеме s1, s1|s2 соответствует схемам s1 и s2.
table	Опциональное поле. Задает паттерн для таблиц в формате Java Pattern. Например, .* соответствует всем таблицам, t1 соответствует таблице t1, t1|t2 соответствует таблицам t1 и t2. Отсутствие значения эквивалентно паттерну .* (все таблицы подходят).
partition_filter	Опциональное поле. Задает фильтр партиции в виде SQL выражения. Выражение может ссылаться на колонки партиции таблицы и использовать стандартные функции. Выражение не может ссылаться на колонки, которые не входят в ключ партиции, а также содержать подзапросы и вызовы табличных функций. Вызов функций происходит от имени специального системного пользователя, на которого не распространяются проверки доступа к функциям. Если значение partition_filter задано, правило не может иметь disable_cache: true. Отсутствие значение эквивалентно фильтру true (все партиции подходят).
distribution_mode	Опциональное поле. Поддерживается только для Hive коннектора. Задает способ сопоставления сплитов с worker-узлами. Допустимые значения: ARBITRARY (значение по умолчанию), PARTITION_KEY. Для повышения эффективности кэша CedrusData стремится обрабатывать конкретный сплит (файл или его часть) на одном и том же узле. В режиме ARBITRARY узел для обработки сплита будет определен путем вычисления хэша пути файла и ряда других свойств сплита. В режиме PARTITION_KEY узел для обработки сплита будет определен путем вычисления хэша от ключа партиции сплита. Данный режим может быть полезен, когда кэшируемая таблица партиционирована, и по крайней мере некоторые запросы используют partitioned режим выполнения запросов.
affinity_mode	Опциональное поле. Задает механизм привязки сплита к узлу. Допустимые значения: FIXED (значение по умолчанию), SOFT. В режиме FIXED сплиты гарантированно будут обработаны на одних их тех же узлах. Это увеличивает hit rate кэша, но может привести к дисбалансу нагрузки в кластере. В режиме SOFT CedrusData будет стремиться обрабатывать сплиты на одних и тех же узлах, но если целевые узлы перегружены, сплит будет отправлен на произвольный узел. Данный режим не гарантирует высокий hit rate кэша, он обеспечивает более равномерную нагрузку на узлы кластера.
affinity_node_count	Опциональное поле. Задает количество узлов на которых может быть выполнен сплит. Увеличение данного значения приводит к дублированию закэшированных в кластере, но обеспечивает более равномерное распределение нагрузки. Если affinity_mode имеет значение SOFT, сплит может быть выполнен на большем количестве узлов, если целевые узлы перегружены. Значение по умолчанию: 1.
disable_cache	Опциональное поле. Позволяет отключить кэширование заданных объектов, соответствующих заданным паттернам schema и table. Значение по умолчанию: false.

Обработка правил происходит в порядке их указания в файле сверху вниз. Проверка, кэшировать ли данные из текущей таблицы или партиции, завершается, как только найдено первое подходящее правило.

Ниже приведен полный пример файла правил, который включает кэширование для всех таблиц схем s1 и s2, кроме таблицы s2.excluded_table, а также для таблицы s3.partitioned_table, в которой закэшированы будут только партиции продаж за последний месяц:

{
  "rules": [
    {
      "schema": "s2",
      "table": "excluded_table",
      "disable_cache": true
    },
    {
      "schema": "s1|s2"
    },
    {
      "schema": "s3",
      "table": "partitioned_table",
      "partition_filter": "sales_date + interval '1' month <= current_date"
    }
  ]
}

Вы можете изменять содержимое файла без перезапуска узла. Повторное чтение содержимого файла происходит периодически в соответствии с параметром конфигурации cedrusdata.hive.data-cache.rules.refresh-period.

Конфигурация

Название	Описание	Значение по умолчанию
cedrusdata.hive.data-cache.enabled	Использовать ли локальный кэш данных. Параметр сессии: cedrusdata_data_cache_enabled.	false
cedrusdata.hive.data-cache.rules.file	Путь к файлу с правилами кэширования в формате JSON.
cedrusdata.hive.data-cache.rules.refresh-period	Как частно повторно считывать правила кэширования из файла, путь к которому задан в cedrusdata.hive.data-cache.rules.file.	1m (одна минута)
cedrusdata.hive.data-cache.rules.partition-filter-time-zone	Имя часового пояса, в контексте которого происходит вычисление предикатов партиций.	Имя текущего часового пояса JVM
cedrusdata.hive.data-cache.rules.cache-size	Размер кэша, в котором хранится решение о кэшировании и скомпилированный предикат партиции (при наличии) для таблиц. Значение 0 отключает кэширование (не рекомендовано).	1000
cedrusdata.hive.data-cache.path	Путь к локальной директории узла, в котором будут сохранены закэшированные данные. Путь должен быть задан в формате file:///<абсолютный путь к директории>. При первом включении кэша CedrusData данная директория должна быть пустой, в противном случае попытка запуска узла завершится ошибкой. Если директория является пустой, то при первом запуске CedrusData создаст скрытый файл в директории, который указывает, что данная директория является локальным кэшем. При перезапуске узла локальный кэш будет повторно инициализирован из директории. При миграции на новую версию CedrusData необходимо вручную очистить директорию кэша, в противном случае попытка запуска узла завершится ошибкой.
cedrusdata.hive.data-cache.max-size	Максимальный размер кэша данных. При превышении размера CedrusData начнет удаление наиболее редко используемых данных. Данный размер учитывает реальный размер данных на диске с учетом возможной компрессии (см. ниже).	100GB
cedrusdata.hive.data-cache.ttl	Максимальное время хранения записи в кэше. По истечении данного времени запись будет удалена из кэша.	1d (один день)
cedrusdata.hive.data-cache.compressor	Режим компрессии закэшированных данных. При отсутствии компрессии данные занимают больше места на диске, но при этом требуют меньше ресурсов CPU для чтения. При включенной компрессии данные занимают меньше месте на диске, но каждая операция чтения потребляет больше CPU. Принимайте решение о включении компрессии на основе того, какой ресурс узла является более дефицитным. Доступные значения: NONE - не сжимать данные, LZ4 - сжимать данные с помощью алгоритма LZ4.	NONE
cedrusdata.hive.data-cache.cleanup-period	Как часто производить очистку кэша от устаревших записей. Запись считается устаревшей, если истек ее TTL, заданный параметром cedrusdata.hive.data-cache.ttl, или если предикат партиции, заданный полем partition_filter правила кэширования, стал возвращать false.	1m (одна минута)
cedrusdata.hive.data-cache.block-row-count	Сколько записей возвращать движку CedrusData при чтении данных из кэша. Используется для тонкой настройки производительности. В большинстве случаев его изменение не требуется.	8192
cedrusdata.hive.data-cache.max-pending-writes	Максимальное количество операций кэширования удаленных данных. Когда CedrusData обнаруживает, что удаленные данные соответствуют заданным правилам кэширования, но отсутствуют в кэше, происходит асинхронное кэширование данных, которое требует повторное удаленное чтение. Таким образом, при прогреве кэша могут возникать всплески сетевой и дисковой I/O активности, которые могут негативно сказаться на производительности текущих запросов. Для уменьшения негативного эффекта вы можете задать максимальное количество запросов на запись данных в кэш.	100000
cedrusdata.hive.data-cache.read-buffer-size	Размер буфера при чтении данных с диска. Увеличения размера буфера приводит к уменьшению количества IOPS, требуемых для чтения данных, но увеличивает потребление памяти. Значение по умолчанию должно хорошо справляться с большинством типичных нагрузок. Настройка данного параметра может быть полезна в облачных окружениях, которые зачастую ограничивают количество IOPS в секунду. Обратите внимание, что размерность «килобайт» необходимо указывать как kB (строчная буква k).	16kB
cedrusdata.hive.data-cache.write-buffer-size	Размер буфера для записи данных на диск. Увеличения размера буфера приводит к уменьшению количества IOPS, требуемых для записи данных, но увеличивает потребление памяти. Значение по умолчанию должно хорошо справляться с большинством типичных нагрузок. Настройка данного параметра может быть полезна в облачных окружениях, которые зачастую ограничивают количество IOPS в секунду. Обратите внимание, что размерность «килобайт» необходимо указывать как kB (строчная буква k).	16kB

Для отчистки кэша конкретного каталога воспользуйтесь встроенной процедурой system.cedrusdata.clear_data_cache. Единственным аргументом процедуры является название каталога. Следующий запрос очищает кэш каталога my_data_lake:

CALL system.cedrusdata.clear_data_cache('my_data_lake');

Статистики работы кэша доступны через таблицу JMX коннектор trino.plugin.hive.datacache:name=<имя каталога>,type=hivedatacacheservice. Следующий запрос отображает текущие статистики кэша каталога my_data_lake:

SELECT * FROM jmx."current"."trino.plugin.hive.datacache:name=my_data_lake,type=hivedatacacheservice"

Оптимизация запросов к partitioned таблицам

Если таблица Hive была создана с параметром partitioned_by, то CedrusData может использовать информацию о схеме партиционирования для выбора более оптимального плана запроса.

Наибольшее ускорение ожидается для запросов, в которых присутствуют операторы Join и Aggregation. Например:

SELECT ...
FROM t1 JOIN t2
ON t1.partitioning_column = t2.other_column

SELECT a, partitioning_column, b, sum(c)
FROM t
GROUP BY a, partitioning_column, b

Ускорение запросов происходит за счет того, что оптимизатор использует информацию о ключе партиционирования для выбора более быстрого способа выполнения того или иного оператора. Например, для осуществления группировки по двум атрибутам GROUP BY a, b CedrusData обычно осуществляет предварительную группировку локально на узлах, после чего пересылает полученные данные между узлами с помощью оператора Exchange, чтобы осуществить финальную группировку:

Parent
  Aggregation[FINAL, groupBy=[a,b]]
    Exchange
      Aggregation[PARTIAL, groupBy=[a,b]]
        TableScan

Если же одна из колонок a или b является ключом партиционирования таблицы, оптимизатор CedrusData использует эту информацию, чтобы осуществить полную группировку локально, тем самым упрощая план запроса:

Parent
  Aggregation[FINAL, groupBy=[a,b]]
    TableScan

Конфигурация

Название	Описание	Значение по умолчанию
cedrusdata.hive.partition-execution	Использовать ли информацию о схеме партиционирования таблиц Hive для оптимизации запросов. Данный параметр будет проигнорирован, если таблица создана с параметром bucketed_by, параметр конфигурации hive.bucket-execution (или параметр сессии bucket_execution_enabled) равен true, а параметр конфигурации cedrusdata.hive.partition-execution.use-when-bucketed (или параметр сессии cedrusdata_partition_execution_use_when_bucketed) равен false. Параметр сессии: cedrusdata_partition_execution_enabled.	true
cedrusdata.hive.partition-execution.use-when-bucketed	Использовать ли информацию о схеме партиционирования таблиц Hive для оптимизации запросов, если таблица содержит параметры partitioned_by и bucketed_by одновременно. Если значение равно false, будет использован набор оптимизаций Trino для bucketed таблиц. Если значение равно true, будет использован набор оптимизаций CedrusData для partitioned таблиц. Включение данного параметра может быть полезно, когда запрос задействует значительно больше партиций таблицы, чем количество бакетов в каждой партиции, или когда запрос содержит join или группировку по колонке партиционирования. В будущем оптимизации partitioned и bucketed таблиц будут объединены, и данный параметр будет удален. Параметр сессии: cedrusdata_partition_execution_use_when_bucketed.	false

Table statistics

The Hive connector supports collecting and managing table statistics to improve query processing performance.

When writing data, the Hive connector always collects basic statistics (numFiles, numRows, rawDataSize, totalSize) and by default will also collect column level statistics:

Available table statistics

Column type	Collectible statistics
TINYINT	Number of nulls, number of distinct values, min/max values
SMALLINT	Number of nulls, number of distinct values, min/max values
INTEGER	Number of nulls, number of distinct values, min/max values
BIGINT	Number of nulls, number of distinct values, min/max values
DOUBLE	Number of nulls, number of distinct values, min/max values
REAL	Number of nulls, number of distinct values, min/max values
DECIMAL	Number of nulls, number of distinct values, min/max values
DATE	Number of nulls, number of distinct values, min/max values
TIMESTAMP	Number of nulls, number of distinct values, min/max values
VARCHAR	Number of nulls, number of distinct values
CHAR	Number of nulls, number of distinct values
VARBINARY	Number of nulls
BOOLEAN	Number of nulls, number of true/false values

Updating table and partition statistics

If your queries are complex and include joining large data sets, running ANALYZE on tables/partitions may improve query performance by collecting statistical information about the data.

When analyzing a partitioned table, the partitions to analyze can be specified via the optional partitions property, which is an array containing the values of the partition keys in the order they are declared in the table schema:

ANALYZE table_name WITH (
    partitions = ARRAY[
        ARRAY['p1_value1', 'p1_value2'],
        ARRAY['p2_value1', 'p2_value2']])

This query will collect statistics for two partitions with keys p1_value1, p1_value2 and p2_value1, p2_value2.

On wide tables, collecting statistics for all columns can be expensive and can have a detrimental effect on query planning. It is also typically unnecessary - statistics are only useful on specific columns, like join keys, predicates, grouping keys. One can specify a subset of columns to be analyzed via the optional columns property:

ANALYZE table_name WITH (
    partitions = ARRAY[ARRAY['p2_value1', 'p2_value2']],
    columns = ARRAY['col_1', 'col_2'])

This query collects statistics for columns col_1 and col_2 for the partition with keys p2_value1, p2_value2.

Note that if statistics were previously collected for all columns, they must be dropped before re-analyzing just a subset:

CALL system.drop_stats('schema_name', 'table_name')

You can also drop statistics for selected partitions only:

CALL system.drop_stats(
    schema_name => 'schema',
    table_name => 'table',
    partition_values => ARRAY[ARRAY['p2_value1', 'p2_value2']])

Dynamic filtering

The Hive connector supports the dynamic filtering optimization. Dynamic partition pruning is supported for partitioned tables stored in any file format for broadcast as well as partitioned joins. Dynamic bucket pruning is supported for bucketed tables stored in any file format for broadcast joins only.

For tables stored in ORC or Parquet file format, dynamic filters are also pushed into local table scan on worker nodes for broadcast joins. Dynamic filter predicates pushed into the ORC and Parquet readers are used to perform stripe or row-group pruning and save on disk I/O. Sorting the data within ORC or Parquet files by the columns used in join criteria significantly improves the effectiveness of stripe or row-group pruning. This is because grouping similar data within the same stripe or row-group greatly improves the selectivity of the min/max indexes maintained at stripe or row-group level.

Delaying execution for dynamic filters

It can often be beneficial to wait for the collection of dynamic filters before starting a table scan. This extra wait time can potentially result in significant overall savings in query and CPU time, if dynamic filtering is able to reduce the amount of scanned data.

For the Hive connector, a table scan can be delayed for a configured amount of time until the collection of dynamic filters by using the configuration property hive.dynamic-filtering.wait-timeout in the catalog file or the catalog session property <hive-catalog>.dynamic_filtering_wait_timeout.

Table redirection

Trino offers the possibility to transparently redirect operations on an existing table to the appropriate catalog based on the format of the table and catalog configuration.

In the context of connectors which depend on a metastore service (for example, Hive коннектор, Iceberg коннектор and Delta Lake коннектор), the metastore (Hive metastore service, AWS Glue Data Catalog) can be used to accustom tables with different table formats. Therefore, a metastore database can hold a variety of tables with different table formats.

As a concrete example, let’s use the following simple scenario which makes use of table redirection:

USE example.example_schema;

EXPLAIN SELECT * FROM example_table;

                               Query Plan
-------------------------------------------------------------------------
Fragment 0 [SOURCE]
     ...
     Output[columnNames = [...]]
     │   ...
     └─ TableScan[table = another_catalog:example_schema:example_table]
            ...

The output of the EXPLAIN statement points out the actual catalog which is handling the SELECT query over the table example_table.

The table redirection functionality works also when using fully qualified names for the tables:

EXPLAIN SELECT * FROM example.example_schema.example_table;

                               Query Plan
-------------------------------------------------------------------------
Fragment 0 [SOURCE]
     ...
     Output[columnNames = [...]]
     │   ...
     └─ TableScan[table = another_catalog:example_schema:example_table]
            ...

Trino offers table redirection support for the following operations:

• Table read operations

  • SELECT

  • DESCRIBE

  • SHOW STATS

  • SHOW CREATE TABLE

• Table write operations

  • INSERT

  • UPDATE

  • MERGE

  • DELETE

• Table management operations

  • ALTER TABLE

  • DROP TABLE

  • COMMENT

Trino does not offer view redirection support.

The connector supports redirection from Hive tables to Iceberg and Delta Lake tables with the following catalog configuration properties:

• hive.iceberg-catalog-name for redirecting the query to Iceberg коннектор

• hive.delta-lake-catalog-name for redirecting the query to Delta Lake коннектор

File system cache

The connector supports configuring and using file system caching.

Performance tuning configuration properties

The following table describes performance tuning properties for the Hive connector.

Предупреждение

Performance tuning configuration properties are considered expert-level features. Altering these properties from their default values is likely to cause instability and performance degradation.

Property name	Description	Default value
hive.max-outstanding-splits	The target number of buffered splits for each table scan in a query, before the scheduler tries to pause.	1000
hive.max-outstanding-splits-size	The maximum size allowed for buffered splits for each table scan in a query, before the query fails.	256 MB
hive.max-splits-per-second	The maximum number of splits generated per second per table scan. This can be used to reduce the load on the storage system. By default, there is no limit, which results in Trino maximizing the parallelization of data access.
hive.max-initial-splits	For each table scan, the coordinator first assigns file sections of up to max-initial-split-size. After max-initial-splits have been assigned, max-split-size is used for the remaining splits.	200
hive.max-initial-split-size	The size of a single file section assigned to a worker until max-initial-splits have been assigned. Smaller splits results in more parallelism, which gives a boost to smaller queries.	32 MB
hive.max-split-size	The largest size of a single file section assigned to a worker. Smaller splits result in more parallelism and thus can decrease latency, but also have more overhead and increase load on the system.	64 MB

Hive 3-related limitations

• For security reasons, the sys system catalog is not accessible.

• Hive’s timestamp with local zone data type is mapped to timestamp with time zone with UTC timezone. It only supports reading values - writing to tables with columns of this type is not supported.

• Due to Hive issues HIVE-21002 and HIVE-22167, Trino does not correctly read TIMESTAMP values from Parquet, RCBinary, or Avro file formats created by Hive 3.1 or later. When reading from these file formats, Trino returns different results than Hive.

• Trino does not support gathering table statistics for Hive transactional tables. You must use Hive to gather table statistics with ANALYZE statement after table creation.