|Feature||Hive 2.x||Hive 3.1.2|
|CREATE EXTERNAL TABLE||✔️||✔️|
|SELECT||✔️ (MapReduce and Tez)||✔️ (MapReduce and Tez)|
|INSERT INTO||✔️ (MapReduce only)️||✔️ (MapReduce only)|
Enabling Iceberg support in Hive #
Loading runtime jar #
To enable Iceberg support in Hive, the
HiveIcebergStorageHandler and supporting classes need to be made available on Hive’s classpath.
These are provided by the
iceberg-hive-runtime jar file.
For example, if using the Hive shell, this can be achieved by issuing a statement like so:
add jar /path/to/iceberg-hive-runtime.jar;
There are many others ways to achieve this including adding the jar file to Hive’s auxiliary classpath so it is available by default. Please refer to Hive’s documentation for more information.
Enabling support #
If the Iceberg storage handler is not in Hive’s classpath, then Hive cannot load or update the metadata for an Iceberg table when the storage handler is set. To avoid the appearance of broken tables in Hive, Iceberg will not add the storage handler to a table unless Hive support is enabled. The storage handler is kept in sync (added or removed) every time Hive engine support for the table is updated, i.e. turned on or off in the table properties. There are two ways to enable Hive support: globally in Hadoop Configuration and per-table using a table property.
Hadoop configuration #
To enable Hive support globally for an application, set
iceberg.engine.hive.enabled=true in its Hadoop configuration.
For example, setting this in the
hive-site.xml loaded by Spark will enable the storage handler for all tables created by Spark.
Starting with Apache Iceberg
0.11.0, when using Hive with Tez you also have to disable vectorization (
Table property configuration #
Alternatively, the property
engine.hive.enabled can be set to
true and added to the table properties when creating the Iceberg table.
Here is an example of doing it programmatically:
Catalog catalog = ...; Map<String, String> tableProperties = Maps.newHashMap(); tableProperties.put(TableProperties.ENGINE_HIVE_ENABLED, "true"); // engine.hive.enabled=true catalog.createTable(tableId, schema, spec, tableProperties);
The table level configuration overrides the global Hadoop configuration.
Catalog Management #
Global Hive catalog #
From the Hive engine’s perspective, there is only one global data catalog that is defined in the Hadoop configuration in the runtime environment. In contrast, Iceberg supports multiple different data catalog types such as Hive, Hadoop, AWS Glue, or custom catalog implementations. Iceberg also allows loading a table directly based on its path in the file system. Those tables do not belong to any catalog. Users might want to read these cross-catalog and path-based tables through the Hive engine for use cases like join.
To support this, a table in the Hive metastore can represent three different ways of loading an Iceberg table,
depending on the table’s
- The table will be loaded using a
HiveCatalogthat corresponds to the metastore configured in the Hive environment if no
- The table will be loaded using a custom catalog if
iceberg.catalogis set to a catalog name (see below)
- The table can be loaded directly using the table’s root location if
iceberg.catalogis set to
For cases 2 and 3 above, users can create an overlay of an Iceberg table in the Hive metastore, so that different table types can work together in the same Hive environment. See CREATE EXTERNAL TABLE and CREATE TABLE for more details.
Custom Iceberg catalogs #
To globally register different catalogs, set the following Hadoop configurations:
|iceberg.catalog.<catalog_name>.type||type of catalog:
|iceberg.catalog.<catalog_name>.catalog-impl||catalog implementation, must not be null if type is empty|
|iceberg.catalog.<catalog_name>.<key>||any config key and value pairs for the catalog|
Here are some examples using Hive CLI:
SET iceberg.catalog.another_hive.type=hive; SET iceberg.catalog.another_hive.uri=thrift://example.com:9083; SET iceberg.catalog.another_hive.clients=10; SET iceberg.catalog.another_hive.warehouse=hdfs://example.com:8020/warehouse;
SET iceberg.catalog.hadoop.type=hadoop; SET iceberg.catalog.hadoop.warehouse=hdfs://example.com:8020/warehouse;
Register an AWS
SET iceberg.catalog.glue.catalog-impl=org.apache.iceberg.aws.GlueCatalog; SET iceberg.catalog.glue.warehouse=s3://my-bucket/my/key/prefix; SET iceberg.catalog.glue.lock-impl=org.apache.iceberg.aws.glue.DynamoLockManager; SET iceberg.catalog.glue.lock.table=myGlueLockTable;
DDL Commands #
CREATE EXTERNAL TABLE #
CREATE EXTERNAL TABLE command is used to overlay a Hive table “on top of” an existing Iceberg table.
Iceberg tables are created using either a
or an implementation of the
and Hive needs to be configured accordingly to operate on these different types of table.
Hive catalog tables #
As described before, tables created by the
HiveCatalog with Hive engine feature enabled are directly visible by the Hive engine, so there is no need to create an overlay.
Custom catalog tables #
For a table in a registered catalog, specify the catalog name in the statement using table property
For example, the SQL below creates an overlay for a table in a
hadoop type catalog named
SET iceberg.catalog.hadoop_cat.type=hadoop; SET iceberg.catalog.hadoop_cat.warehouse=hdfs://example.com:8020/hadoop_cat; CREATE EXTERNAL TABLE database_a.table_a STORED BY 'org.apache.iceberg.mr.hive.HiveIcebergStorageHandler' TBLPROPERTIES ('iceberg.catalog'='hadoop_cat');
iceberg.catalog is missing from both table properties and the global Hadoop configuration,
HiveCatalog will be used as default.
Path-based Hadoop tables #
Iceberg tables created using
HadoopTables are stored entirely in a directory in a filesystem like HDFS.
These tables are considered to have no catalog.
To indicate that, set
iceberg.catalog property to
location_based_table. For example:
CREATE EXTERNAL TABLE table_a STORED BY 'org.apache.iceberg.mr.hive.HiveIcebergStorageHandler' LOCATION 'hdfs://some_bucket/some_path/table_a' TBLPROPERTIES ('iceberg.catalog'='location_based_table');
CREATE TABLE #
Hive also supports directly creating a new Iceberg table through
CREATE TABLE statement. For example:
CREATE TABLE database_a.table_a ( id bigint, name string ) PARTITIONED BY ( dept string ) STORED BY 'org.apache.iceberg.mr.hive.HiveIcebergStorageHandler';
to Hive, the table appears to be unpartitioned although the underlying Iceberg table is partitioned.
Due to the limitation of Hive
PARTITIONED BYsyntax, if you use Hive
CREATE TABLE, currently you can only partition by columns, which is translated to Iceberg identity partition transform. You cannot partition by other Iceberg partition transforms such as
days(timestamp). To create table with all partition transforms, you need to create the table with other engines like Spark or Flink.
Custom catalog table #
You can also create a new table that is managed by a custom catalog. For example, the following code creates a table in a custom Hadoop catalog:
SET iceberg.catalog.hadoop_cat.type=hadoop; SET iceberg.catalog.hadoop_cat.warehouse=hdfs://example.com:8020/hadoop_cat; CREATE TABLE database_a.table_a ( id bigint, name string ) PARTITIONED BY ( dept string ) STORED BY 'org.apache.iceberg.mr.hive.HiveIcebergStorageHandler' TBLPROPERTIES ('iceberg.catalog'='hadoop_cat');
If the table to create already exists in the custom catalog, this will create a managed overlay table. This means technically you can omit the
EXTERNALkeyword when creating an overlay table. However, this is not recommended because creating managed overlay tables could pose a risk to the shared data files in case of accidental drop table commands from the Hive side, which would unintentionally remove all the data in the table.
DROP TABLE #
Tables can be dropped using the
DROP TABLE command:
DROP TABLE [IF EXISTS] table_name [PURGE];
You can configure purge behavior through global Hadoop configuration or Hive metastore table properties:
|external.table.purge||true||if all data and metadata should be purged in a table by default|
Each Iceberg table’s default purge behavior can also be configured through Iceberg table properties:
|gc.enabled||true||if all data and metadata should be purged in the table by default|
gc.enabled on the Iceberg table via
external.table.purge is also updated on HMS table accordingly.
external.table.purge as a table prop during Hive
gc.enabled is pushed down accordingly to the Iceberg table properties.
This makes sure that the 2 properties are always consistent at table level between Hive and Iceberg.
ALTER TABLE SET TBLPROPERTIESdoes not update
gc.enabledon the Iceberg table. This is a limitation on Hive 3.1.2 because the
HiveMetaHookdoesn’t have all the hooks for alter tables yet.
Querying with SQL #
Here are the features highlights for Iceberg Hive read support:
- Predicate pushdown: Pushdown of the Hive SQL
WHEREclause has been implemented so that these filters are used at the Iceberg
TableScanlevel as well as by the Parquet and ORC Readers.
- Column projection: Columns from the Hive SQL
SELECTclause are projected down to the Iceberg readers to reduce the number of columns read.
- Hive query engines: Both the MapReduce and Tez query execution engines are supported.
Here are the Hadoop configurations that one can adjust for the Hive reader:
|iceberg.mr.reuse.containers||false||if Avro reader should reuse containers|
|iceberg.mr.case.sensitive||true||if the query is case-sensitive|
You should now be able to issue Hive SQL
SELECT queries and see the results returned from the underlying Iceberg table, for example:
SELECT * from table_a;
Writing with SQL #
Here are the Hadoop configurations that one can adjust for the Hive writer:
|iceberg.mr.commit.table.thread.pool.size||10||the number of threads of a shared thread pool to execute parallel commits for output tables|
|iceberg.mr.commit.file.thread.pool.size||10||the number of threads of a shared thread pool to execute parallel commits for files in each output table|
INSERT INTO #
Hive supports the standard single-table
INSERT INTO operation:
INSERT INTO table_a VALUES ('a', 1); INSERT INTO table_a SELECT ...;
Multi-table insert is also supported, but it will not be atomic and are committed one table at a time. Partial changes will be visible during the commit process and failures can leave partial changes committed. Changes within a single table will remain atomic.
Here is an example of inserting into multiple tables at once in Hive SQL:
FROM customers INSERT INTO target1 SELECT customer_id, first_name INSERT INTO target2 SELECT last_name, customer_id;
Type compatibility #
Hive and Iceberg support different set of types. Iceberg can perform type conversion automatically, but not for all combinations, so you may want to understand the type conversion in Iceberg in prior to design the types of columns in your tables. You can enable auto-conversion through Hadoop configuration (not enabled by default):
|iceberg.mr.schema.auto.conversion||false||if Hive should perform type auto-conversion|
Hive type to Iceberg type #
This type conversion table describes how Hive types are converted to the Iceberg types. The conversion applies on both creating Iceberg table and writing to Iceberg table via Hive.
|timestamp||timestamp without timezone|
|timestamplocaltz||timestamp with timezone||Hive 3 only|