# Model configurations

While ReOrc provides the [metadata panel](/asset-management/metadata.md) for basic model configuration, you can use the `config()` macro (provided by dbt) to implement more granular and powerful controls over your model's behavior. This macro allows you to define model-specific configurations directly in your SQL files, giving you precise control over how your models are built and materialized.

## Key features of the `config()` macro

1. **Materialization control**: The `config()` macro enables users to determine how a model will be materialized in the analytics database. Common materialization strategies include:
   * **Table**: The model is created as a table.
   * **View**: The model is created as a view.
   * **Incremental**: The model is built incrementally, allowing for efficient updates to large datasets.
2. **Granular control**: Configurations set using the `config()` macro can inherit or override settings defined in other locations like model's metadata. Users can define various configurations within the `config()` macro, some of which include:
   * Setting unique keys for incremental models
   * Specifying incremental strategy
   * Specifying partition for large data volume
   * Configuring pre-hook and post-hook

The configuration should be placed at the beginning of model script:

```sql
{{ config(
    materialized='incremental',
    unique_key='id'
) }}

SELECT *
FROM {{ ref('source_table') }}
```

## Configure incremental models

One popular usage of `config()` is to define the incremental strategy for data models.

Incremental is materialization strategy designed to efficiently update tables in a data warehouse by only transforming and loading new or changed data since the last run. This approach significantly reduces the time and resources required for data transformations, making it especially useful for large datasets.

In a model's metadata panel, you can specify the materialization option to be `incremental`. By default, this option results in append-only behavior, where new data is simply added to the table with each build. Therefore, you must specify the following configurations:

* **`unique_key`**: Defines the unique identifier for records in the model, which helps dbt determine whether to insert new records or update existing ones.
* **`incremental_strategy`**: Specifies how dbt should handle incremental updates. Common strategies include:
  * `merge`: Updates existing records and inserts new ones based on the unique key.
  * `append`: Simply adds new records without updating existing ones.
  * `insert_overwrite`: Overwrites existing records with new data based on specified conditions.
* **`is_incremental()`**: This macro is essential for filtering which rows should be processed during an incremental run. It allows you to specify conditions to select only new or updated records since the last execution.

For example, in the orders table, we can implement incremental materialization to process only new or updated orders since the last run, reducing the processing time and ensuring the table remains up-to-date:

```sql
{{ config(
    materialized='incremental',
    unique_key='id',
    incremental_strategy='merge'
) }}

select * 
from {{ source("public", "raw_orders") }}
{% if is_incremental() %} -- only process new records
    where ordered_at >= (select max(ordered_at) from {{ this }})
{% endif %}
```

## Platform-specific congfigurations

As different database platforms use varying approaches to optimize data processing, some configurations are designed and applied specifically for each platform. For detailed information on these platform-specific configurations and behaviors, refer to [PLATFORM SPECIFIC](/platform-specific/doris-selectdb.md)


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