# Amazon S3 Reference

> All S3 authentication options and data type handling for files on S3.

#  Amazon S3 Reference

Authentication options and data type handling for [S3 connections](../connect/s3.md).

## Authentication

| Variable | Example | Description |
|---|---|---|
| `DATACONTRACT_S3_REGION` | `eu-central-1` | Region of the S3 bucket |
| `DATACONTRACT_S3_ACCESS_KEY_ID` | `AKIAXV5Q5Q...` | AWS Access Key ID |
| `DATACONTRACT_S3_SECRET_ACCESS_KEY` | `93S7LRrJ...` | AWS Secret Access Key |
| `DATACONTRACT_S3_SESSION_TOKEN` | `AQoDYXdzEJr...` | AWS temporary session token (optional) |

If `DATACONTRACT_S3_ACCESS_KEY_ID` is not set, no credentials are configured — public buckets and ambient credentials still work. For S3-compatible storage (MinIO), set `endpointUrl` in the `servers` block; the CLI then uses path-style addressing.

## Data types

Files on S3 are read with DuckDB. Type handling depends on the `format` in the `servers` block:

| `format` | How types are handled |
|---|---|
| `csv` | The file is read **as the contract's types** — no type checks are generated; a value that can't be coerced surfaces as a read error. |
| `json` | Same as CSV, plus every record is validated against a JSON Schema derived from the contract's `logicalType`s (with `format` options like `date-time`, `uuid`). |
| `parquet` | Column types come from the Parquet file; the contract's `logicalType` is checked by category (`Check that field x has type y`). |
| `delta` | Column types come from the Delta table; the contract's `logicalType` is checked by category. |

`physicalType` is never checked against file sources — declare `logicalType` (and `logicalTypeOptions` for value constraints). See [Local files](./local.md) for how CSV/JSON imports infer types.

{/* AUTOGENERATED TYPE MAPPING: do not edit by hand; regenerate with update_reference_types.py */}

### Logical type mapping

When no `physicalType` is declared, the CLI derives the DuckDB column type from the `logicalType` when reading files. This table is generated from the converters in the CLI's code:

| `logicalType` | CSV read type | Parquet read type |
|---|---|---|
| `string` | `VARCHAR` | `VARCHAR` |
| `integer` | `BIGINT` | `INTEGER` |
| `number` | `DOUBLE` | `DECIMAL` |
| `boolean` | `BOOLEAN` | `BOOLEAN` |
| `date` | `DATE` | `DATE` |
| `timestamp` | `TIMESTAMP` | `TIMESTAMP WITH TIME ZONE` |
| `time` | `TIME` | `TIME` |
| `object` | `VARCHAR` | `STRUCT()` |
| `array` | `VARCHAR` | `VARCHAR[]` |

{/* END AUTOGENERATED TYPE MAPPING */}