Hive Data Types

The following table shows the mappings from Hive to Dremio data types. If there are additional Hive types not listed in the table, then those types are not supported in Dremio.

Data Type Mappings

Hive Database Type	Dremio Type
BINARY	VARBINARY
BOOLEAN	BOOLEAN
BYTE	INTEGER
CHAR	VARCHAR
DATE	DATE
DECIMAL	DECIMAL
DOUBLE	DOUBLE
FLOAT	FLOAT
INT	INTEGER
LONG	BIGINT
SHORT	INTEGER
STRING	VARCHAR
TIMESTAMP	TIMESTAMP
VARCHAR	VARCHAR

Complex Data Types

Dremio supports LIST, MAP, and STRUCT complex data types in source files that are in these formats:

• Apache Iceberg
• Apache Parquet
• Delta Lake
• ORC
• RCFile
• SequenceFile
• Text

Dremio supports the UNION data type in source files that are in these formats:

• Apache Iceberg
• Apache Parquet
• Delta Lake
• SequenceFile

Dremio does not support the UNION data type in source files that are in ORC, RCFile, or text format.

For descriptions of these data types, see Summary of Supported Data Types in Dremio.

Complex Data Type Mapping

Hive Database Type	Dremio Type
ARRAY	LIST
STRUCT	STRUCT

Examples for LIST, STRUCT, and UNION

The following examples assume that the table, HiveOrcTable, exists in Hive and has the following structure:

HiveOrcTable Table Structure

Column Name	Hive Data Type
list_field	ARRAY<INT>
struct_field	STRUCT<field_name:INT, field_name2:STRING>

LIST example

In this example, list_field is the column name whose data type is ARRAY in Hive:

Query a column containing a LIST

SELECT list_field[0] from HiveOrcTable

STRUCT example

In this example, struct_field is the column name whose data type is STRUCT in Hive:

Query a column containing STRUCT fields

SELECT struct_field['field_name'] from HiveOrcTable

Implicit Type Casting for Parquet-formatted Files

Dremio implicitly casts data types from Parquet-formatted files that differ from the defined schema of a Hive table. Each row in the table below represents the data type in a Parquet-formatted file, and the columns represent the data types defined in the schema of the Hive table. For example, if the data type of a named column in the Parquet file is INT and the data type of the column with the same name in the Hive table is either INT or BIGINT, Dremio will implicitly cast to that data type.

	BOOLEAN	INT	BIGINT	FLOAT	DOUBLE	DECIMAL	DATE	TIMESTAMP	VARBINARY
BOOLEAN to	Yes
INT to		Yes	Yes
BIGINT to			Yes
FLOAT to				Yes	Yes
DOUBLE to					Yes
DECIMAL to						Yes
DATE to							Yes
TIMESTAMP to								Yes
VARBINARY to									Yes

In addition, Dremio can implicitly cast VARCHAR to VARCHAR. However, this conversion is not enabled by default. To enable implicit casting of VARCHAR to VARCHAR, run the following command on the Hive table:

Enable implicit casting of VARCHAR to VARCHAR

alter table <tableName> set enable_varchar_truncation=true

To disable implicit casting of VARCHAR to VARCHAR, run the following command on the Hive table:

Disable implicit casting of VARCHAR to VARCHAR

alter table <tableName> set enable_varchar_truncation=false

Dremio applies the following rules for numerical conversions:

• Dremio returns null if a conversion results in overflow during runtime.
• Dremio truncates data and proceeds with a query if a conversion results in truncation.
• Dremio implicitly converts differences of precision, scale, and length for DECIMAL and VARCHAR data types.