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

<AgentInstructions>

## Submitting Feedback

If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback:

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```json
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  "path": "/reference-sql/functions-reference/iceberg/read_iceberg",
  "feedback": "Description of the issue"
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</AgentInstructions>

> Reference material for READ_ICEBERG function

# READ_ICEBERG

A table-valued function (TVF) that reads data from [Apache Iceberg](https://iceberg.apache.org/) tables. The function can use either a [location object](/reference-sql/commands/data-definition/create-location-iceberg) or individual TVF parameters to access the data, and can read from file-based catalogs as well as REST catalogs. `READ_ICEBERG` returns a table with data from the specified Iceberg table.

**Topics:**

* [Syntax](#syntax)
* [Parameters](#parameters)
* [Return Type](#return-type)
* [Best Practices](#best-practices)
* [Examples](#examples)
  * [Simplifying queries with views](#simplifying-queries-with-views)
* [About Metadata Versions in File-Based Catalogs](#about-metadata-versions-in-file-based-catalogs)
* [Limitations](#limitations)

## Syntax

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
-- Using a LOCATION object (credentials stored in LOCATION)
READ_ICEBERG (
  LOCATION => '<location_name>'
  [, NAMESPACE => '<namespace_name>' ]
  [, TABLE => '<table_name>' ]
  [, MAX_STALENESS => <max_staleness_allowed> ]
)

-- Using individual TVF parameters
READ_ICEBERG (
  URL => '<s3_or_rest_api_url>'
  -- Parameters for Iceberg REST catalogs
  [, WAREHOUSE => '<warehouse_name>' ]
  [, NAMESPACE => '<namespace_name>' ]
  [, TABLE => '<table_name>' ]
  -- Parameters for Amazon S3
  [, AWS_ACCESS_KEY_ID = '<aws_access_key_id>' ]
  [, AWS_SECRET_ACCESS_KEY = '<aws_secret_access_key>' ]
  [, AWS_SESSION_TOKEN = '<aws_session_token>' ]
  [, AWS_ROLE_ARN = '<aws_role_arn>' ]
  [, AWS_ROLE_EXTERNAL_ID = '<aws_role_external_id>' ]
  -- Parameters for OAuth authentication
  [, OAUTH_CLIENT_ID => '<oauth_client_id>' ]
  [, OAUTH_CLIENT_SECRET = '<oauth_client_secret>' ]
  [, OAUTH_SCOPE => '<oauth_scope>' ]
  [, OAUTH_SERVER_URL => '<oauth_server_url>' ]
  [, BEARER_TOKEN => '<bearer_token>' ]
  -- Other common parameters
  [, MAX_STALENESS => <max_staleness_allowed> ]
)
```

## Parameters

### Using a LOCATION object

| Parameter       | Description                                                                                                                                                                                                                                                                                                                                                                                           | Supported input types |
| :-------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :-------------------- |
| `LOCATION`      | The name of a location object that contains the Iceberg parameters and credentials. Firebolt recommends using `LOCATION` to store credentials for authentication. `LOCATION` must be specified as a string literal (e.g., `LOCATION => 'my_location'`). Unlike `URL`, it cannot be used as a positional parameter.                                                                                    | `TEXT`                |
| `NAMESPACE`     | The namespace an Iceberg table resides in. Used only for REST catalogs.                                                                                                                                                                                                                                                                                                                               | `TEXT`                |
| `TABLE`         | The name of the Iceberg table to read. Used only for REST catalogs.                                                                                                                                                                                                                                                                                                                                   | `TEXT`                |
| `MAX_STALENESS` | Specifies a maximum staleness for results returned by this function, e.g., `INTERVAL '30 seconds'`. The default value is 0 seconds, forcing Firebolt to fetch the latest version metadata from the catalog for every query. Values larger than zero instruct Firebolt to cache metadata and vended credentials in memory, and can typically reduce query latency by tens or hundreds of milliseconds. | `INTERVAL`            |

For a comprehensive guide to LOCATION objects, see [LOCATION objects](/guides/security/location). For syntax details, see [CREATE LOCATION (Iceberg)](/reference-sql/commands/data-definition/create-location-iceberg).

### Using individual TVF parameters

#### Common Parameters

| Parameter       | Description                                                                                                                                                                                                                                                                                                                                                                                           | Supported input types |
| :-------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :-------------------- |
| `URL`           | A url pointing to a table in an Iceberg file-based catalog, or a url pointing to an Iceberg REST catalog API endpoint. For file-based catalogs, the expected format is `s3://{bucket_name}/{path}/{to}/{table}` or `s3://{bucket_name}/{path}/{to}/{table}/metadata/{version.metadata.json}`. For REST catalogs, the expected format is `https://{path}/{to}/{rest}/{host}`.                          | `TEXT`                |
| `MAX_STALENESS` | Specifies a maximum staleness for results returned by this function, e.g., `INTERVAL '30 seconds'`. The default value is 0 seconds, forcing Firebolt to fetch the latest version metadata from the catalog for every query. Values larger than zero instruct Firebolt to cache metadata and vended credentials in memory, and can typically reduce query latency by tens or hundreds of milliseconds. | `INTERVAL`            |

#### Common Parameters for Iceberg REST catalogs

The following parameters are used for all REST catalogs, including AWS Glue catalogs accessed via REST endpoint.

| Parameter   | Description                                            | Supported input types |
| :---------- | :----------------------------------------------------- | :-------------------- |
| `WAREHOUSE` | The name of the warehouse an Iceberg table resides in. | `TEXT`                |
| `NAMESPACE` | The namespace an Iceberg table resides in.             | `TEXT`                |
| `TABLE`     | The name of the Iceberg table to read.                 | `TEXT`                |

#### Amazon S3 Parameters

The following parameters are used for authentication to both file-based catalogs and AWS Glue catalogs.

| Parameter               | Description                | Supported input types |
| :---------------------- | :------------------------- | :-------------------- |
| `AWS_ACCESS_KEY_ID`     | The AWS access key ID.     | `TEXT`                |
| `AWS_SECRET_ACCESS_KEY` | The AWS secret access key. | `TEXT`                |
| `AWS_SESSION_TOKEN`     | The AWS session token.     | `TEXT`                |
| `AWS_ROLE_ARN`          | The AWS role ARN.          | `TEXT`                |
| `AWS_ROLE_EXTERNAL_ID`  | The AWS role external ID.  | `TEXT`                |

#### Parameters for OAuth authentication

The following parameters apply to REST catalogs that use OAuth for authentication.

| Parameter             | Description                                                                                                                  | Supported input types |
| :-------------------- | :--------------------------------------------------------------------------------------------------------------------------- | :-------------------- |
| `OAUTH_CLIENT_ID`     | An OAuth client ID for authenticating to the REST catalog. .                                                                 | `TEXT`                |
| `OAUTH_CLIENT_SECRET` | An OAuth client secret for authenticating to the REST catalog.                                                               | `TEXT`                |
| `OAUTH_SCOPE`         | An OAuth scope for authenticating to the REST catalog.                                                                       | `TEXT`                |
| `OAUTH_SERVER_URL`    | The URL to use when requesting an access token for the REST catalog. If not specified, `{URL}/v1/oauth/tokens` will be used. | `TEXT`                |
| `BEARER_TOKEN`        | An OAuth bearer token to use as an access token for the REST catalog.                                                        | `TEXT`                |

## Return Type

The result is a table with data from the Iceberg files. Columns are read and parsed using their inferred data types.

## Best practices

* Use a `LOCATION` object to store credentials for authentication. This approach centralizes credential management and eliminates the need to specify individual credential parameters in each query. See [CREATE LOCATION (Iceberg)](/reference-sql/commands/data-definition/create-location-iceberg).
* **Use views to simplify repeated queries.** Wrap `READ_ICEBERG` in a [view](/reference-sql/commands/data-definition/create-view) so you can query Iceberg tables without repeating the TVF call. See [example below](#simplifying-queries-with-views).
* Specifying a value for `MAX_STALENESS` can help improve performance in tight loops and infrequently-updated tables.
* It is recommended to specify all parameters using the named-parameter syntax rather than relying on parameter positions. For example: use `URL => 'http://example.com'` rather than omitting the `URL =>` parameter name specifier.

## Examples

### Simplifying queries with views

You can wrap `READ_ICEBERG` TVFs in a view for easier querying of Iceberg tables. This also works with `LOCATION`-based `READ_ICEBERG` calls.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
CREATE VIEW lineitem AS SELECT * FROM READ_ICEBERG(
    URL => 's3://firebolt-core-us-east-1/test_data/tpch/iceberg/tpch.db/lineitem'
  );

SELECT * FROM lineitem LIMIT 10;

CREATE VIEW orders AS SELECT * FROM READ_ICEBERG(
    URL => 's3://firebolt-core-us-east-1/test_data/tpch/iceberg/tpch.db/orders'
  );

SELECT * FROM orders LIMIT 10;
```

Once views are created, you can use them in joins and complex queries without referencing `READ_ICEBERG` directly:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT o.o_orderkey, l.l_extendedprice
FROM orders o
JOIN lineitem l ON o.o_orderkey = l.l_orderkey
WHERE o.o_orderdate > '1995-01-01'
LIMIT 10;
```

For more information about views, see [CREATE VIEW](/reference-sql/commands/data-definition/create-view).

### Reading using a LOCATION

The following code example reads the first 5 rows from an Iceberg table using a `LOCATION` object:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
CREATE LOCATION my_location
WITH 
  SOURCE = ICEBERG
  CATALOG = FILE_BASED
  CATALOG_OPTIONS = (
    URL = 's3://my-bucket/path/to/iceberg/table'
  )
  CREDENTIALS = ( AWS_ACCESS_KEY_ID = '1231' AWS_SECRET_ACCESS_KEY = '567' );

SELECT *
FROM READ_ICEBERG(
  LOCATION => 'my_location',
  MAX_STALENESS => INTERVAL '30 seconds'
)
LIMIT 5;
```

`LOCATION` objects are supported for file-based (S3-hosted) catalogs as well as REST catalogs.
For more examples of `LOCATION`, see [CREATE LOCATION (Iceberg)](/reference-sql/commands/data-definition/create-location-iceberg).

### Using TVF parameters, from a public location in S3

The following code example reads the first 5 rows from an Iceberg table in a file-based catalog stored on S3:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT * 
FROM READ_ICEBERG(
  URL => 's3://firebolt-publishing-public/help_center_assets/firebolt_sample_iceberg/tpch/iceberg/lineitem',
  MAX_STALENESS => INTERVAL '30 seconds'
) 
LIMIT 5;
```

**Returns**

| l\_orderkey | l\_partkey | l\_suppkey | l\_linenumber | l\_quantity | l\_extendedprice | l\_discount | l\_tax | l\_returnflag | l\_linestatus | l\_shipdate | l\_commitdate | l\_receiptdate | l\_shipinstruct   | l\_shipmode | l\_comment                        |
| :---------- | :--------- | :--------- | :------------ | :---------- | :--------------- | :---------- | :----- | :------------ | :------------ | :---------- | :------------ | :------------- | :---------------- | :---------- | :-------------------------------- |
| 1           | 156        | 4          | 1             | 17.00       | 17954.55         | 0.04        | 0.02   | N             | O             | 1996-03-13  | 1996-02-12    | 1996-03-22     | DELIVER IN PERSON | TRUCK       | to beans x-ray carefull           |
| 1           | 68         | 9          | 2             | 36.00       | 34850.16         | 0.09        | 0.06   | N             | O             | 1996-04-12  | 1996-02-28    | 1996-04-20     | TAKE BACK RETURN  | MAIL        | according to the final foxes. qui |
| 1           | 64         | 5          | 3             | 8.00        | 7712.48          | 0.10        | 0.02   | N             | O             | 1996-01-29  | 1996-03-05    | 1996-01-31     | TAKE BACK RETURN  | REG AIR     | ourts cajole above the furiou     |
| 1           | 3          | 6          | 4             | 28.00       | 25284.00         | 0.09        | 0.06   | N             | O             | 1996-04-21  | 1996-03-30    | 1996-05-16     | NONE              | AIR         | s cajole busily above t           |
| 1           | 25         | 8          | 5             | 24.00       | 22200.48         | 0.10        | 0.04   | N             | O             | 1996-03-30  | 1996-03-14    | 1996-04-01     | NONE              | FOB         | the regular, regular pa           |

### Using a direct path to a metadata.json file

A URL pointing to an Iceberg metadata.json file will also return the same result:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT * 
FROM READ_ICEBERG(
  URL => 's3://firebolt-publishing-public/help_center_assets/firebolt_sample_iceberg/tpch/iceberg/lineitem/metadata/00001-2b7ef7c8-a1d8-4239-abf5-41df838d20ba.metadata.json',
  MAX_STALENESS => INTERVAL '30 seconds'
) 
LIMIT 5;
```

**Returns**

| l\_orderkey | l\_partkey | l\_suppkey | l\_linenumber | l\_quantity | l\_extendedprice | l\_discount | l\_tax | l\_returnflag | l\_linestatus | l\_shipdate | l\_commitdate | l\_receiptdate | l\_shipinstruct   | l\_shipmode | l\_comment                        |
| :---------- | :--------- | :--------- | :------------ | :---------- | :--------------- | :---------- | :----- | :------------ | :------------ | :---------- | :------------ | :------------- | :---------------- | :---------- | :-------------------------------- |
| 1           | 156        | 4          | 1             | 17.00       | 17954.55         | 0.04        | 0.02   | N             | O             | 1996-03-13  | 1996-02-12    | 1996-03-22     | DELIVER IN PERSON | TRUCK       | to beans x-ray carefull           |
| 1           | 68         | 9          | 2             | 36.00       | 34850.16         | 0.09        | 0.06   | N             | O             | 1996-04-12  | 1996-02-28    | 1996-04-20     | TAKE BACK RETURN  | MAIL        | according to the final foxes. qui |
| 1           | 64         | 5          | 3             | 8.00        | 7712.48          | 0.10        | 0.02   | N             | O             | 1996-01-29  | 1996-03-05    | 1996-01-31     | TAKE BACK RETURN  | REG AIR     | ourts cajole above the furiou     |
| 1           | 3          | 6          | 4             | 28.00       | 25284.00         | 0.09        | 0.06   | N             | O             | 1996-04-21  | 1996-03-30    | 1996-05-16     | NONE              | AIR         | s cajole busily above t           |
| 1           | 25         | 8          | 5             | 24.00       | 22200.48         | 0.10        | 0.04   | N             | O             | 1996-03-30  | 1996-03-14    | 1996-04-01     | NONE              | FOB         | the regular, regular pa           |

### Authenticated read from S3

The following code examples use various valid combinations of AWS secrets to read from S3:

**Using access key + secret:**

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT * 
FROM READ_ICEBERG(
  URL => 's3://my-bucket/path/to/iceberg/table',
  AWS_ACCESS_KEY_ID => '1231',
  AWS_SECRET_ACCESS_KEY => '567',
  MAX_STALENESS => INTERVAL '30 seconds'
) 
LIMIT 5;
```

**Using access key, secret, and session token:**

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT * 
FROM READ_ICEBERG(
  URL => 's3://my-bucket/path/to/iceberg/table',
  AWS_ACCESS_KEY_ID => '1231',
  AWS_SECRET_ACCESS_KEY => '567',
  AWS_SESSION_TOKEN => 'session-token',
  MAX_STALENESS => INTERVAL '30 seconds'
) 
LIMIT 5;
```

**Using role:**

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT * 
FROM READ_ICEBERG(
  URL => 's3://my-bucket/path/to/iceberg/table',
  AWS_ROLE_ARN => 'arn:aws:iam::123456789012:role/S3Access',
  MAX_STALENESS => INTERVAL '30 seconds'
) 
LIMIT 5;
```

**Using role + external id:**

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT * 
FROM READ_ICEBERG(
  URL => 's3://my-bucket/path/to/iceberg/table',
  AWS_ROLE_ARN => 'arn:aws:iam::123456789012:role/S3Access',
  AWS_ROLE_EXTERNAL_ID => 'my-role-external-id',
  MAX_STALENESS => INTERVAL '30 seconds'
) 
LIMIT 5;
```

### Reading from REST

The following code example reads the first 5 rows from an Iceberg table in a REST catalog:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT *
FROM READ_ICEBERG(
  URL => 'https://my-iceberg-rest-catalog/api',
  WAREHOUSE  => 'my_warehouse',
  NAMESPACE => 'my_namespace',
  TABLE => 'my_table_name',
  OAUTH_CLIENT_ID => '00000000-0000-0000-0000-000000000000',
  OAUTH_CLIENT_SECRET => '1234',
  OAUTH_SCOPE => 'example_permission:all',
  MAX_STALENESS => INTERVAL '30 seconds'
)
LIMIT 5;
```

For more on Iceberg REST catalogs, see the [Iceberg REST API spec](https://github.com/apache/iceberg/blob/main/open-api/rest-catalog-open-api.yaml).

### Reading from REST, with a custom OAuth token URL

Some Iceberg REST catalogs do not support the `/v1/oauth/tokens` API, and serve OAuth tokens from a different API. For these catalogs, specify `OAUTH_SERVER_URL`.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT *
FROM READ_ICEBERG(
  URL => 'https://my-iceberg-rest-catalog/api',
  WAREHOUSE  => 'my_warehouse',
  NAMESPACE => 'my_namespace',
  TABLE => 'my_table_name',
  OAUTH_CLIENT_ID => '00000000-0000-0000-0000-000000000000',
  OAUTH_CLIENT_SECRET => '1234',
  OAUTH_SCOPE => 'example_permission:all',
  OAUTH_SERVER_URL => 'https://my-iceberg-rest-catalog/example/token',
  MAX_STALENESS => INTERVAL '30 seconds'
)
LIMIT 5;
```

### Reading from Databricks Unity Catalog

One example of an Iceberg REST catalog that requires a custom `OAUTH_SERVER_URL` is the [Databricks Unity Catalog](https://docs.databricks.com/aws/en/data-governance/unity-catalog/). The following code example reads the first 5 rows from a table in a Databricks Unity Catalog, showing how Databricks concepts map to `READ_ICEBERG` parameters:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT *
FROM READ_ICEBERG(
  URL => 'https://000-0000000000000.cloud.databricks.com/api/2.1/unity-catalog/iceberg-rest
  WAREHOUSE  => 'my_uc_catalog_name',
  NAMESPACE => 'my_uc_schema_name',
  TABLE => 'my_table_name',
  OAUTH_CLIENT_ID => '00000000-0000-0000-0000-000000000000',
  OAUTH_CLIENT_SECRET => '1234',
  OAUTH_SCOPE => 'all-apis',
  OAUTH_SERVER_URL => 'https://000-0000000000000.cloud.databricks.com/oidc/v1/token',
  MAX_STALENESS => INTERVAL '30 seconds'
)
LIMIT 5;
```

If you're using a PAT [Databricks - Authenticate with Databricks personal access tokens (legacy)](https://docs.databricks.com/aws/en/dev-tools/auth/pat), you can pass it via the `BEARER_TOKEN` parameter.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT *
FROM READ_ICEBERG(
  URL => 'https://000-0000000000000.cloud.databricks.com/api/2.1/unity-catalog/iceberg/v1'
  WAREHOUSE  => 'my_uc_catalog_name',
  NAMESPACE => 'my_uc_schema_name',
  TABLE => 'my_table_name',
  BEARER_TOKEN => '00000000-0000-0000-0000-000000000000',
  MAX_STALENESS => INTERVAL '30 seconds'
)
LIMIT 5;
```

For configuring Unity Catalog in your Databricks workspace, see [Databricks - Set up and manage Unity Catalog](https://docs.databricks.com/aws/en/data-governance/unity-catalog/get-started). Note that you will need to enable credential vending in your Unity Catalog, see [Databricks - Unity Catalog credential vending for external system access](https://docs.databricks.com/aws/en/external-access/credential-vending).
For general information about reading Databricks tables from Iceberg clients, see [Databricks - Read Databricks tables from Iceberg clients](https://docs.databricks.com/gcp/en/external-access/iceberg).

### Reading from Snowflake Open Catalog

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT *
FROM READ_ICEBERG(
  URL => 'https://abc123.us-west-2.aws.myapi.com/polaris/api/catalog',
  WAREHOUSE  => 'my_warehouse',
  NAMESPACE => 'my_catalog_name',
  TABLE => 'my_table_name',
  OAUTH_CLIENT_ID => '00000000-0000-0000-0000-000000000000',
  OAUTH_CLIENT_SECRET => '1234',
  OAUTH_SCOPE => 'PRINCIPAL_ROLE:ALL',
  MAX_STALENESS => INTERVAL '30 seconds'
)
LIMIT 5;
```

For setting up a Snowflake Open Catalog in your account, see [Snowflake - Snowflake Open Catalog overview](https://other-docs.snowflake.com/en/opencatalog/overview). Note that you will need to enable credential vending for your Iceberg tables, see [Snowflake - Use catalog-vended credentials for Apache Iceberg™ tables](https://docs.snowflake.com/en/user-guide/tables-iceberg-configure-catalog-integration-vended-credentials).
For general information about reading Snowflake Open Catalog tables from Iceberg clients, see [Snowflake - Checking your REST catalog configuration](https://docs.snowflake.com/en/user-guide/tables-iceberg-configure-catalog-integration-rest-check-config).

### Reading from AWS Glue catalog

The following code example reads the first 5 rows from an Iceberg table in an AWS Glue catalog. Note that for AWS Glue catalogs, the `warehouse` parameter maps to `catalog_id` and the `namespace` parameter maps to `database`:

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT *
FROM READ_ICEBERG(
  URL => 'https://glue.us-west-2.amazonaws.com/iceberg',
  WAREHOUSE  => '123456789123',
  NAMESPACE => 'my_database',
  TABLE => 'my_table',
  AWS_ACCESS_KEY_ID => '1231',
  AWS_SECRET_ACCESS_KEY => '567',
  AWS_SESSION_TOKEN => 'session-token'
)
LIMIT 5;
```

Firebolt supports authentication using either Lake Formation or direct access to underlying storage. For authentication details, refer to the AWS Glue Catalog section in [CREATE LOCATION (Iceberg)](/reference-sql/commands/data-definition/create-location-iceberg#aws-glue-catalog).

## About Metadata Versions in File-Based Catalogs

When reading from a file-based catalog, Firebolt first looks for a `version-hint.text` file to determine the metadata version. If this file is unavailable, you can instead specify a direct path to a specific `metadata.json` file.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT *
FROM READ_ICEBERG(
  URL => 's3://my-bucket/path/to/iceberg/table/metadata/v1.metadata.json',
  ...
)
LIMIT 5;
```

Alternatively, Firebolt can also attempt to 'guess' the correct metadata file. Because this approach may violate atomicity guarantees, it is disabled by default. For details, see [Guessing Iceberg metadata version](/reference-sql/system-settings#guessing-iceberg-metadata-version).

## Limitations

* Iceberg tables with Parquet data files in S3 are currently supported.
* Versions 1 and 2 of the Apache Iceberg specification are supported.
* Tables with following Iceberg features are currently not supported:
  * Row-level deletes (position deletes or equality deletes)
  * Schema evolution
  * Partition evolution
* The following data types are currently not supported:
  * `variant`
  * `geometry`
  * `geography`
* Reading past snapshots with time travel is currently not supported.
* Nested complex types such as `struct`, `list`, and `map` are currently read as nullable even if Iceberg defines the field to be non-nullable. This only applies to nested complex types (`struct`/`list`/`map` nested inside another `struct`/`list`/`map`).
* [Returning partition values for Identity Transforms from partition metadata](https://iceberg.apache.org/spec/#column-projection) is currently not supported.
* By default, cross-region reads for S3 are disabled for `read_iceberg`, as they may incur additional costs. They may be enabled on a per-query basis using the [cross\_region\_request\_mode](/reference-sql/system-settings#access-cross-region-data) setting.