> ## Documentation Index
> Fetch the complete documentation index at: https://docs.e6data.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Data types

> Ingest Engine currently supports a limited set of primitive types, shown in the table below. Because every Ingest Engine pipeline is a compiled Rust crate, each type has a corresponding Rust type.

Ingest Engine leverages [Apache DataFusion](https://arrow.apache.org/datafusion/) for SQL support. DataFusion is in turn a part of the [Apache Arrow](https://arrow.apache.org/) project, a cross-language data format for columnar in-memory computation.

Depending on which part of the system you're working with one or more of these will be relevant. For basic SQL users you should only need to deal with the SQL types.

These types can also be inserted as literals in sql. For types like INT vs BIGINT it will infer the type based on context.

| Ingest Engine | Rust | Python | Arrow | Sql Types | Example Literals |
| - | - | - | - | - | - |
| `Boolean` | `bool` | `bool` | `Boolean` | `BOOLEAN` | `TRUE`, `FALSE` |
| `Int32` | `i32` | `int` | `Int32` | `INT`, `INTEGER` | `0`, `1`, `-2` |
| `Int64` | `i64` | `int` | `Int64` | `BIGINT` | `0`, `1`, `-2` |
| `Uint32` | `u32` | `int` | `UInt32` | `INT UNSIGNED`, `INTEGER UNSIGNED` | `0`, `1`, `2` |
| `Uint64` | `u64` | `int` | `UInt64` | `BIGINT UNSIGNED` | `0`, `1`, `2` |
| `Float32` | `f32` | `float` | `Float32` | `FLOAT`, `REAL` | `0.0`, `-2.4`, `1E-3` |
| `Float64` | `f64` | `float` | `Float64` | `DOUBLE` | `0.0`, `-2.4`, `1E-35` |
| `Decimal128` | `i128` | - | `Decimal128` | `DECIMAL(precision, scale)` | `123.45`, `0.001` |
| `String` | `String` | `str` | `Utf8` | `VARCHAR`, `CHAR`, `TEXT`, `STRING` | `"hello"`, `"world"` |
| `Timestamp` | `SystemTime` | - | `Timestamp` | `TIMESTAMP` | `'2020-01-01'`, `'2023-05-17T22:16:00.648662+00:00'` |
| `Bytes` | `Vec<u8>` | - | `Binary` | `BYTEA` | `X'A123'` (hex) |

## Composite types

In addition to the primitive types above, Ingest Engine SQL supports two forms of composite types: arrays and structs.

### Array types

Arrays group together zero or more elements of the same type. Arrays are declared by suffixing another type with `[]`, for example an INT array can be declared with `INT[]`. Arrays values can be indexed using 1-indexed subscript notation (`v[1]` is the first element of `v`).

Arrays can be constructed via `[]` literals, like `[1, 2, 3]`.

Ingest Engine provides a set of [array functions](/ingest/sql/functions/array) for manipulating array values; arrays may also be unnested using the [`UNNEST` operator](/ingest/sql/reference/basic-queries#unnest-operator).

### Struct types

Structs allow combining related fields into a single value. Structs are declared using this syntax: `struct<field_name field_type, ..>`, and may contain any other type, including arrays and other structs.

For example:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
CREATE TABLE events (
    properties STRUCT <
      user_id TEXT,
      timings INT[],
      name STRUCT <
        first TEXT,
        last TEXT
      >
    >
)
```

Structs fields can be accessed via `.` notation, for example `properties.name.first`.


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