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Hive Data Types

Dremio supports selecting the following Hive Database types. The following table shows the mappings from Hive to Dremio data types.

Note: If a type is not present in the table, it is not currently supported.

Data Type Mappings

Hive Database Type	Dremio Type
BINARY	varbinary
BOOLEAN	boolean
BYTE	integer
CHAR	varchar
DATE	date
DECIMAL	double
DOUBLE	double
FLOAT	float
INT	integer
LONG	bigint
SHORT	integer
STRING	varchar
TIMESTAMP	timestamp
VARCHAR	varchar

Complex Data Types

As of Dremio 4.3.0, Dremio supports the following complex data types:

LIST: Supports extracting list elements using list indices.
STRUCT: Supports extracting struct fields using field names within single quotes.
UNION: Supports reading data from Union type field from Hive ORC tables.

Complex Data Type Mapping

Hive Database Type	Dremio Type
ARRAY	LIST
STRUCT	STRUCT
UNIONTYPE	UNION

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
struct_field	STRUCT<field_name:INT, field_name2:STRING>
union_field	UNIONTYPE<INT, STRING>

LIST example

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

SELECT list_field[0] from HiveOrcTable

STRUCT example

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

SELECT struct_field[‘field_name’] from HiveOrcTable

UNION example

In this example, union_field is the column name whose data type is UNIONTYPE in Hive:

SELECT union_field FROM HiveOrcTable

Implicit Type Casting for Parquet-formatted Files

Dremio implictly 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:

alter table <tableName> set enable_varchar_truncation=true

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

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.