# In-Memory Arrow Data Accelerator

The In-Memory Arrow Data Accelerator is the default data accelerator in Spice. It uses Apache Arrow to store data in-memory for fast access and query performance.

### Configuration <a href="#configuration" id="configuration"></a>

To use the In-Memory Arrow Data Accelerator, no additional configuration is required beyond enabling acceleration.

Example:

```yaml
datasets:
  - from: spice.ai:path.to.my_dataset
    name: my_dataset
    acceleration:
      enabled: true
```

However Arrow can be specified explicitly using `arrow` as the `engine` for acceleration.

```yaml
datasets:
  - from: spice.ai:path.to.my_dataset
    name: my_dataset
    acceleration:
      enabled: true
      engine: arrow
```

{% hint style="warning" %}
**Limitations**

* The In-Memory Arrow Data Accelerator does not support persistent storage. Data is stored in-memory and will be lost when the Spice runtime is stopped.
* The In-Memory Arrow Data Accelerator does not support `Decimal256` (76 digits), as it exceeds Arrow's maximum Decimal width of 38 digits.
* The In-Memory Arrow Data Accelerator does not support [indexes](https://docs.spiceai.org/features/data-acceleration/indexes).
* The In-Memory Arrow Data Accelerator only supports primary-key [constraints](https://docs.spiceai.org/features/data-acceleration/constraints), not `unique` constraints.
* With Arrow acceleration, mathematical operations like `value1 / value2` are treated as integer division if the values are integers. For example, `1 / 2` will result in 0 instead of the expected 0.5. Use casting to FLOAT to ensure conversion to a floating-point value: `CAST(1 AS FLOAT) / CAST(2 AS FLOAT)` (or `CAST(1 AS FLOAT) / 2`).
  {% endhint %}