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# Data Types

DataFusion uses Arrow, and thus the Arrow type system, for query
execution. The SQL types from
[sqlparser-rs](https://github.com/sqlparser-rs/sqlparser-rs/blob/main/src/ast/data_type.rs#L27)
are mapped to [Arrow data types](https://docs.rs/arrow/latest/arrow/datatypes/enum.DataType.html) 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.

[implementing user defined types and custom metadata in datafusion]: https://datafusion.apache.org/blog/2025/09/21/custom-types-using-metadata

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

```sql
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:

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

The older syntax still works as well:

```sql
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`     |

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.

## Numeric Types

| SQL DataType                                     | Arrow DataType                 |
| ------------------------------------------------ | :----------------------------- |
| `TINYINT`                                        | `Int8`                         |
| `SMALLINT`                                       | `Int16`                        |
| `INT` or `INTEGER`                               | `Int32`                        |
| `BIGINT`                                         | `Int64`                        |
| `TINYINT UNSIGNED`                               | `UInt8`                        |
| `SMALLINT UNSIGNED`                              | `UInt16`                       |
| `INT UNSIGNED` or `INTEGER UNSIGNED`             | `UInt32`                       |
| `BIGINT UNSIGNED`                                | `UInt64`                       |
| `FLOAT`                                          | `Float32`                      |
| `REAL`                                           | `Float32`                      |
| `DOUBLE`                                         | `Float64`                      |
| `DECIMAL(precision, scale)` where precision ≤ 38 | `Decimal128(precision, scale)` |
| `DECIMAL(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`    | `Boolean`      |

## Binary Types

| SQL DataType | Arrow DataType |
| ------------ | :------------- |
| `BYTEA`      | `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`.

## Unsupported SQL Types

| SQL Data Type | Arrow DataType      |
| ------------- | :------------------ |
| `UUID`        | _Not yet supported_ |
| `BLOB`        | _Not yet supported_ |
| `CLOB`        | _Not yet supported_ |
| `BINARY`      | _Not yet supported_ |
| `VARBINARY`   | _Not yet supported_ |
| `REGCLASS`    | _Not yet supported_ |
| `NVARCHAR`    | _Not yet supported_ |
| `CUSTOM`      | _Not yet supported_ |
| `ARRAY`       | _Not yet supported_ |
| `ENUM`        | _Not yet supported_ |
| `SET`         | _Not yet supported_ |
| `DATETIME`    | _Not yet supported_ |
