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

# atoti.AutoMultiColumnArrayConversion

### *final class* atoti.AutoMultiColumnArrayConversion

Pass it to a DirectQuery `*ConnectionConfig` class to automatically convert all external tables with array values stored with one element per column to tables with array columns.

### Example

```pycon theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
>>> import os
>>> from atoti_directquery_snowflake import ConnectionConfig, TableConfig
>>> url = f"jdbc:snowflake://{os.environ['SNOWFLAKE_ACCOUNT_IDENTIFIER']}.snowflakecomputing.com/?user={os.environ['SNOWFLAKE_USERNAME']}&database=TEST_RESOURCES&schema=TESTS"
>>> connection_config = ConnectionConfig(
...     url=url,
...     auto_multi_column_array_conversion=tt.AutoMultiColumnArrayConversion(
...         separator="_",
...         threshold=3,
...     ),
...     password=os.environ["SNOWFLAKE_PASSWORD"],
... )
>>> external_database = session.connect_to_external_database(connection_config)
>>> external_table = external_database.tables[
...     "TUTORIAL", "MULTI_COLUMN_QUANTITY"
... ]
```

In the external database, `external_table` has this content:

| PRODUCT    | QUANTITY\_0 | QUANTITY\_1 | QUANTITY\_2 | QUANTITY\_3 | QUANTITY\_4 |
| ---------- | ----------- | ----------- | ----------- | ----------- | ----------- |
| product\_1 | 10          | 20          | 15          | 25          | 10          |
| product\_2 | 50          | 65          | 55          | 30          | 80          |

It has 5 QUANTITY\{separator}\{index} columns (where [`separator`](#atoti.AutoMultiColumnArrayConversion.separator) is `"_"`).
Since 5 is greater than the [`threshold`](#atoti.AutoMultiColumnArrayConversion.threshold) passed above, the automatic conversion will activate and these 5 columns will be merged into an array column:

```pycon theme={"languages":{"custom":["/engine/python-sdk/0.9/languages/pycon.tmLanguage.json"]}}
>>> list(external_table)
['PRODUCT', 'QUANTITY']
>>> table = session.add_external_table(
...     external_table,
...     config=TableConfig(keys={"PRODUCT"}),
...     table_name="Sales (Multi column array)",
... )
>>> table.head().sort_index()
                                 QUANTITY
PRODUCT
product_1  [10.0, 20.0, 15.0, 25.0, 10.0]
product_2  [50.0, 65.0, 55.0, 30.0, 80.0]
```

<Callout icon="link">
  **See also**:
  [`MultiColumnArrayConversion`](./atoti.directquery.array_conversion.multi_column_array_conversion#atoti.MultiColumnArrayConversion).
</Callout>

#### separator *: [str](https://docs.python.org/3/library/stdtypes.html#str)* *= ''*

The characters separating the array column name and the element index.

#### threshold *: [int](https://docs.python.org/3/library/functions.html#int)* *= 50*

The minimum number of columns with the same prefix required to trigger the automatic conversion.