ClickHouse/docs/en/sql-reference/table-functions/s3.md

---
slug: /en/sql-reference/table-functions/s3
sidebar_position: 180
sidebar_label: s3
keywords: [s3, gcs, bucket]
---

# s3 Table Function

Provides a table-like interface to select/insert files in [Amazon S3](https://aws.amazon.com/s3/) and [Google Cloud Storage](https://cloud.google.com/storage/). This table function is similar to the [hdfs function](../../sql-reference/table-functions/hdfs.md), but provides S3-specific features.

If you have multiple replicas in your cluster, you can use the [s3Cluster function](../../sql-reference/table-functions/s3Cluster.md) instead to parallelize inserts.

When using the `s3 table function` with [`INSERT INTO...SELECT`](../../sql-reference/statements/insert-into#inserting-the-results-of-select), data is read and inserted in a streaming fashion. Only a few blocks of data reside in memory while the blocks are continuously read from S3 and pushed into the destination table.

**Syntax**

``` sql
s3(path [, NOSIGN | aws_access_key_id, aws_secret_access_key [,session_token]] [,format] [,structure] [,compression])
```

:::tip GCS
The S3 Table Function integrates with Google Cloud Storage by using the GCS XML API and HMAC keys.  See the [Google interoperability docs]( https://cloud.google.com/storage/docs/interoperability) for more details about the endpoint and HMAC.

For GCS, substitute your HMAC key and HMAC secret where you see `aws_access_key_id` and `aws_secret_access_key`.
:::

**Arguments**

- `path` — Bucket url with path to file. Supports following wildcards in readonly mode: `*`, `**`, `?`, `{abc,def}` and `{N..M}` where `N`, `M` — numbers, `'abc'`, `'def'` — strings. For more information see [here](../../engines/table-engines/integrations/s3.md#wildcards-in-path).

  :::note GCS
  The GCS path is in this format as the endpoint for the Google XML API is different than the JSON API:
  ```
  https://storage.googleapis.com/<bucket>/<folder>/<filename(s)>
  ```
  and not ~~https://storage.cloud.google.com~~.
  :::

- `NOSIGN` - If this keyword is provided in place of credentials, all the requests will not be signed.
- `access_key_id`, `secret_access_key` — Keys that specify credentials to use with given endpoint. Optional.
- `session_token` - Session token to use with the given keys. Optional when passing keys.
- `format` — The [format](../../interfaces/formats.md#formats) of the file.
- `structure` — Structure of the table. Format `'column1_name column1_type, column2_name column2_type, ...'`.
- `compression` — Parameter is optional. Supported values: `none`, `gzip/gz`, `brotli/br`, `xz/LZMA`, `zstd/zst`. By default, it will autodetect compression by file extension.

**Returned value**

A table with the specified structure for reading or writing data in the specified file.

**Examples**

Selecting the first 5 rows from the table from S3 file `https://datasets-documentation.s3.eu-west-3.amazonaws.com/aapl_stock.csv`:

``` sql
SELECT *
FROM s3(
   'https://datasets-documentation.s3.eu-west-3.amazonaws.com/aapl_stock.csv',
   'CSVWithNames'
)
LIMIT 5;
```

```response
┌───────Date─┬────Open─┬────High─┬─────Low─┬───Close─┬───Volume─┬─OpenInt─┐
│ 1984-09-07 │ 0.42388 │ 0.42902 │ 0.41874 │ 0.42388 │ 23220030 │       0 │
│ 1984-09-10 │ 0.42388 │ 0.42516 │ 0.41366 │ 0.42134 │ 18022532 │       0 │
│ 1984-09-11 │ 0.42516 │ 0.43668 │ 0.42516 │ 0.42902 │ 42498199 │       0 │
│ 1984-09-12 │ 0.42902 │ 0.43157 │ 0.41618 │ 0.41618 │ 37125801 │       0 │
│ 1984-09-13 │ 0.43927 │ 0.44052 │ 0.43927 │ 0.43927 │ 57822062 │       0 │
└────────────┴─────────┴─────────┴─────────┴─────────┴──────────┴─────────┘
```

:::note
ClickHouse uses filename extensions to determine the format of the data. For example, we could have run the previous command without the `CSVWithNames`:

``` sql
SELECT *
FROM s3(
   'https://datasets-documentation.s3.eu-west-3.amazonaws.com/aapl_stock.csv'
)
LIMIT 5;
```

ClickHouse also can determine the compression of the file. For example, if the file was zipped up with a `.csv.gz` extension, ClickHouse would decompress the file automatically.
:::


## Usage

Suppose that we have several files with following URIs on S3:

- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/some_prefix/some_file_1.csv'
- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/some_prefix/some_file_2.csv'
- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/some_prefix/some_file_3.csv'
- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/some_prefix/some_file_4.csv'
- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/another_prefix/some_file_1.csv'
- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/another_prefix/some_file_2.csv'
- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/another_prefix/some_file_3.csv'
- 'https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/another_prefix/some_file_4.csv'

Count the amount of rows in files ending with numbers from 1 to 3:

``` sql
SELECT count(*)
FROM s3('https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/{some,another}_prefix/some_file_{1..3}.csv', 'CSV', 'name String, value UInt32')
```

``` text
┌─count()─┐
│      18 │
└─────────┘
```

Count the total amount of rows in all files in these two directories:

``` sql
SELECT count(*)
FROM s3('https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/{some,another}_prefix/*', 'CSV', 'name String, value UInt32')
```

``` text
┌─count()─┐
│      24 │
└─────────┘
```

:::tip
If your listing of files contains number ranges with leading zeros, use the construction with braces for each digit separately or use `?`.
:::

Count the total amount of rows in files named `file-000.csv`, `file-001.csv`, … , `file-999.csv`:

``` sql
SELECT count(*)
FROM s3('https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/big_prefix/file-{000..999}.csv', 'CSV', 'name String, value UInt32');
```

``` text
┌─count()─┐
│      12 │
└─────────┘
```

Insert data into file `test-data.csv.gz`:

``` sql
INSERT INTO FUNCTION s3('https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/test-data.csv.gz', 'CSV', 'name String, value UInt32', 'gzip')
VALUES ('test-data', 1), ('test-data-2', 2);
```

Insert data into file `test-data.csv.gz` from existing table:

``` sql
INSERT INTO FUNCTION s3('https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/test-data.csv.gz', 'CSV', 'name String, value UInt32', 'gzip')
SELECT name, value FROM existing_table;
```

Glob ** can be used for recursive directory traversal. Consider the below example, it will fetch all files from `my-test-bucket-768` directory recursively:

``` sql
SELECT * FROM s3('https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/**', 'CSV', 'name String, value UInt32', 'gzip');
```

The below get data from all `test-data.csv.gz` files from any folder inside `my-test-bucket` directory recursively:

``` sql
SELECT * FROM s3('https://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/**/test-data.csv.gz', 'CSV', 'name String, value UInt32', 'gzip');
```

Note. It is possible to specify custom URL mappers in the server configuration file. Example: 
``` sql
SELECT * FROM s3('s3://clickhouse-public-datasets/my-test-bucket-768/**/test-data.csv.gz', 'CSV', 'name String, value UInt32', 'gzip');
```
The URL `'s3://clickhouse-public-datasets/my-test-bucket-768/**/test-data.csv.gz'` would be replaced to `'http://clickhouse-public-datasets.s3.amazonaws.com/my-test-bucket-768/**/test-data.csv.gz'`


Custom mapper can be added into `config.xml`:
``` xml
<url_scheme_mappers>
   <s3>
      <to>https://{bucket}.s3.amazonaws.com</to>
   </s3>
   <gs>
      <to>https://{bucket}.storage.googleapis.com</to>
   </gs>
   <oss>
      <to>https://{bucket}.oss.aliyuncs.com</to>
   </oss>
</url_scheme_mappers>
```

## Partitioned Write

If you specify `PARTITION BY` expression when inserting data into `S3` table, a separate file is created for each partition value. Splitting the data into separate files helps to improve reading operations efficiency.

**Examples**

1. Using partition ID in a key creates separate files:

```sql
INSERT INTO TABLE FUNCTION
    s3('http://bucket.amazonaws.com/my_bucket/file_{_partition_id}.csv', 'CSV', 'a String, b UInt32, c UInt32')
    PARTITION BY a VALUES ('x', 2, 3), ('x', 4, 5), ('y', 11, 12), ('y', 13, 14), ('z', 21, 22), ('z', 23, 24);
```
As a result, the data is written into three files: `file_x.csv`, `file_y.csv`, and `file_z.csv`.

2. Using partition ID in a bucket name creates files in different buckets:

```sql
INSERT INTO TABLE FUNCTION
    s3('http://bucket.amazonaws.com/my_bucket_{_partition_id}/file.csv', 'CSV', 'a UInt32, b UInt32, c UInt32')
    PARTITION BY a VALUES (1, 2, 3), (1, 4, 5), (10, 11, 12), (10, 13, 14), (20, 21, 22), (20, 23, 24);
```
As a result, the data is written into three files in different buckets: `my_bucket_1/file.csv`, `my_bucket_10/file.csv`, and `my_bucket_20/file.csv`.

## Accessing public buckets

ClickHouse tries to fetch credentials from many different types of sources.
Sometimes, it can produce problems when accessing some buckets that are public causing the client to return `403` error code.
This issue can be avoided by using `NOSIGN` keyword, forcing the client to ignore all the credentials, and not sign the requests.

``` sql
SELECT *
FROM s3(
   'https://datasets-documentation.s3.eu-west-3.amazonaws.com/aapl_stock.csv',
   NOSIGN,
   'CSVWithNames'
)
LIMIT 5;
```

## Virtual Columns {#virtual-columns}

- `_path` — Path to the file. Type: `LowCardinalty(String)`.
- `_file` — Name of the file. Type: `LowCardinalty(String)`.
- `_size` — Size of the file in bytes. Type: `Nullable(UInt64)`. If the file size is unknown, the value is `NULL`.

## Storage Settings {#storage-settings}

- [s3_truncate_on_insert](/docs/en/operations/settings/settings.md#s3_truncate_on_insert) - allows to truncate file before insert into it. Disabled by default.
- [s3_create_multiple_files](/docs/en/operations/settings/settings.md#s3_allow_create_multiple_files) - allows to create a new file on each insert if format has suffix. Disabled by default.
- [s3_skip_empty_files](/docs/en/operations/settings/settings.md#s3_skip_empty_files) - allows to skip empty files while reading. Disabled by default.

**See Also**

- [S3 engine](../../engines/table-engines/integrations/s3.md)