Data Types

DataFusion uses Arrow, and thus the Arrow type system, for query execution. The SQL types from sqlparser-rs are mapped to Arrow data types according to the following table. This mapping occurs when defining the schema in a CREATE EXTERNAL TABLE command or when performing a SQL CAST operation.

For background on extension types and custom metadata, see the Implementing User Defined Types and Custom Metadata in DataFusion blog.

You can see the corresponding Arrow type for any SQL expression using the arrow_typeof function. For example:

select arrow_typeof(interval '1 month');
+---------------------------------------------------------------------+
| arrow_typeof(IntervalMonthDayNano("79228162514264337593543950336")) |
+---------------------------------------------------------------------+
| Interval(MonthDayNano)                                              |
+---------------------------------------------------------------------+

You can cast a SQL expression to a specific Arrow type using the arrow_cast function For example, to cast the output of now() to a Timestamp with second precision:

select arrow_cast(now(), 'Timestamp(s)') as "now()";
+---------------------+
| now()               |
+---------------------+
| 2025-10-24T20:02:45 |
+---------------------+

The older syntax still works as well:

select arrow_cast(now(), 'Timestamp(Second, None)') as "now()";
+---------------------+
| now()               |
+---------------------+
| 2023-03-03T17:19:21 |
+---------------------+

Character Types

SQL DataType	Arrow DataType
CHAR	Utf8View
VARCHAR	Utf8View
TEXT	Utf8View
STRING	Utf8View
CHARACTER VARYING	Utf8View
CHAR VARYING	Utf8View
NVARCHAR	Utf8View

By default, string types are mapped to Utf8View. This can be configured using the datafusion.sql_parser.map_string_types_to_utf8view setting. When set to false, string types are mapped to Utf8 instead.

Note that CHAR, VARCHAR, STRING, CHARACTER VARYING, CHAR VARYING, and NVARCHAR can optionally receive the maximum length (e.g., VARCHAR(n)). However, this limit is ignored. To raise an error when the length is passed, set datafusion.sql_parser.support_varchar_with_length to false.

Numeric Types

SQL DataType	Arrow DataType
TINYINT	Int8
SMALLINT or INT2	Int16
INT or INTEGER or INT4	Int32
BIGINT or INT8	Int64
TINYINT UNSIGNED or UTINYINT	UInt8
SMALLINT UNSIGNED or INT2 UNSIGNED or USMALLINT	UInt16
INT UNSIGNED or INTEGER UNSIGNED or INT4 UNSIGNED	UInt32
BIGINT UNSIGNED or INT8 UNSIGNED or UBIGINT	UInt64
FLOAT or FLOAT4 or REAL	Float32
DOUBLE or DOUBLE PRECISION or FLOAT8	Float64
DECIMAL(precision, scale) or NUMERIC(precision, scale) where precision ≤ 38	Decimal128(precision, scale)
DECIMAL(precision, scale) or NUMERIC(precision, scale) where precision > 38	Decimal256(precision, scale)

The maximum supported precision for DECIMAL types is 76.

Date/Time Types

SQL DataType	Arrow DataType
DATE	Date32
TIME	Time64(Nanosecond)
TIMESTAMP	Timestamp(Nanosecond, None)
INTERVAL	Interval(IntervalMonthDayNano)

Boolean Types

SQL DataType	Arrow DataType
BOOLEAN or BOOL	Boolean

Binary Types

SQL DataType	Arrow DataType
BYTEA	Binary
BLOB	Binary
BINARY	Binary
VARBINARY	Binary
BYTES	Binary

You can create binary literals using a hex string literal such as X'1234' to create a Binary value of two bytes, 0x12 and 0x34.

Nested Types

SQL DataType	Arrow DataType
ARRAY<T> or T[]	List(T)
T[n]	FixedSizeList(n x T)
MAP(k, v)	Map(k, v)
STRUCT<[c0] T0[, ..., [cn] Tn]>	Struct(c0: T0[, ..., cn: Tn])

While columns defined with STRUCT require all rows to have the same schema, MAP imposes no such restriction.

Also note that STRUCT can be declared without defining the field names. In that case, they will be set to c0, c1, …, cn.

Unsupported SQL Types

SQL Data Type	Arrow DataType
UUID	Not yet supported
CLOB	Not yet supported
REGCLASS	Not yet supported
CUSTOM	Not yet supported
ENUM	Not yet supported
SET	Not yet supported
DATETIME	Not yet supported