# Custom

Components that allow to create custom user-defined procedures and SQL queries in your workflows.

## Call Procedure

**Description**

This component executes an arbitrary CALL SQL statement.

Use *$a* and *$b* as placeholders for the input table names (you can use one, both, or none of them), and *$output* as placeholder for the output table name.

The procedure that you are calling is responsible for creating the output table in the path stored in the *$output* variable.

The following is a valid example of code to use in this component:

``CALL MY_PROCEDURE($a, 10, `$output`);``

{% hint style="info" %}
Please take into account that `$a, $b and $output`will be parsed directly as they are. In some cases, the table names that work as input/output need to be quoted differently depending on the data warehouse. **Users need to ensure the correct quoting**, like `` `$output` `` or `"$a"`.
{% endhint %}

{% hint style="info" %}
Due to Redshift limitations, calling stored procedures that have INOUT string parameters will cause an exception when running the workflow. Stored procedures with such parameters are not supported.
{% endhint %}

#### Additional placeholders

* `$isStoredProcedure`

When using the **Workflows API** or workflows as **MCP Tool**, your workflow is executed as a **stored procedure** within your data warehouse. This changes how tables are handled.

To manage this behavior, we provide the `$isStoredProcedure` placeholder. This will be replaced with `true` when the workflow is run as a stored procedure. This happens when running workflows[ via API](/carto-user-manual/workflows/executing-workflows-via-api.md).

In stored procedures:

* Table names are **not fully qualified**
* Tables are expected to be **temporary** and **session-scoped**

Your SQL code should account for this logic to avoid errors when running workflows in API mode.

Here is a sample code for that (notice that no CALL is made in this case, since the component can run any arbitrary SQL code):

**Example:**

```
IF ($isStoredProcedure) THEN
  -- $output will be a simple table name (i.e mytable)
  CREATE TEMPORARY TABLE $output AS SELECT * FROM $a LIMIT 10;
ELSE
  -- $output will be a fully qualified name (i.e database.schema.mytable)
  CREATE TABLE $output AS SELECT * FROM $a LIMIT 10;
END IF
```

* `$dryrun`

Workflows use a **dry run** mode to infer and propagate table schemas across components. When executing queries in this mode, you may want to differentiate logic from a standard run.

To handle this, use the `$dryrun` placeholder, which is replaced by `true` when the workflow is being dry-run (e.g., when clicking "Validate schema").

**Example:**

```
IF ($dryrun) THEN
  -- During dry run: propagate schema so other components can recognize output
  CREATE TABLE `$output` AS SELECT * FROM `$a`;
ELSE
  -- During normal run: actually create output tables
  CREATE TABLE `$output` AS SELECT * FROM `$a`;

  -- During normal run: write to a specific target table for post-processing
  CREATE OR REPLACE TABLE `project.schema.specific_table` AS SELECT * FROM `$a`;
END IF;
```

**Inputs**

* `Source table [Table]`
* `Source table [Table]`
* `SQL CALL statement [String]`

**Outputs**

* `Result table [Table]`

## Custom Python Code

**Description**

This component runs arbitrary Python code.

**Inputs**

1. **Source table:** Use `df_a`in your code to reference a dataframe that contains the data in the input. Use `$a` to reference the FQN of the input table in your code.
2. **Source table:** Use `df_b`in your code to reference a dataframe that contains the data in the input. Use `$b` to reference the FQN of the input table in your code.
3. **Source table:** Use `df_c`in your code to reference a dataframe that contains the data in the input. Use `$c` to reference the FQN of the input table in your code.

**Settings**

* **Python code:** Define your custom python code that will be executed by the component.

**Outputs**

* **Output table:** Use `df_output`in your code to reference a dataframe that contains the data in the output. Use `$output` to reference the FQN of the output table in your code.

## Custom SQL Select

**Description**

This component executes an arbitrary SELECT SQL statement.

A new table will be created from the result of the entered statement

Use *$a, $b* and *$c* as placeholders for the input table names (you can use one, all, or none of them).

The following is a valid example of code to use in this component, which will generate a new table with an added area column (based on a column named 'geom'), with only the rows corresponding to the five largest geometries:

``SELECT *, ST_AREA(geom) AS area FROM `$a` ORDER BY area LIMIT 5``

{% hint style="info" %}
Please take into account that `$a, $b and $c`will be parsed directly as they are. In some cases, they will need to be quoted differently depending on the data warehouse. **Users need to ensure the correct quoting**, like `'$a'` or `"$a"`.
{% endhint %}

{% hint style="info" %}
When using Workflows' variables in your Custom SQL code, remember that they don't need to be wrapped into curly brackets like `{{ @var_name}}`. Variables can be used directly as `@var_name` inside your Custom SQL code.
{% endhint %}

{% hint style="danger" %}
Please **avoid trailing semi-colon** `;`in your Custom SQL code as it might cause unexpected behavior.
{% endhint %}

**Inputs**

* `Source table [Table]`
* `Source table [Table]`
* `SQL SELECT statement [String]`

**Outputs**

* `Result table [Table]`


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