Ephemeral Materialization

Ephemeral Materialization

Unlike other materializations, ephemeral models don't create database objects. Instead, dbt incorporates the model's code into dependent models using Common Table Expressions (CTEs).

This means:

• No physical tables or views are created

• Code is integrated into downstream models

• Logic can be reused across models

Ephemeral models are ideal for lightweight, reusable transformations that don't need to be queried directly.

---

Working with Ephemeral Models

Let's understand ephemeral models through a simple example:

-- models/intermediate/clean_customer_data.sql
{{
    config(
        materialized='ephemeral'
    )
}}

SELECT
    customer_id,
    TRIM(first_name) as first_name,
    TRIM(last_name) as last_name,
    LOWER(email) as email
FROM {{ ref('raw_customers') }}

When this model is referenced:

1. No table or view is created

2. The code becomes a CTE in downstream models

3. The logic is recomputed each time it's used

---

When to Use Ephemeral Models

Ephemeral models work best for:

• Simple transformations (cleaning, filtering)

• Early-stage models in your DAG

• Light data preparation steps

• Code that supports 1-2 downstream models

---

Configuration

Model-Level Configuration

-- In your model SQL file
{{
    config(
        materialized='ephemeral'
    )
}}

SELECT 
    user_id,
    CASE 
        WHEN age < 18 THEN 'youth'
        WHEN age < 65 THEN 'adult'
        ELSE 'senior'
    END as age_category
FROM {{ ref('raw_users') }}

---

Performance and Usage Guidelines

Advantages and Limitations

Advantages	Limitations
🧹 Reduces database clutter	🚫 Can't query directly
♻️ Enables code reuse	⚠️ No model contracts support
📦 No storage overhead	🔍 Harder to debug
🔄 Flexible logic updates	🛠️ Limited operational use

When to Change Materialization

Consider a different materialization when you:

• Need to query the model directly

• Have complex transformations

• Support many downstream models

• Require model contracts

Best Practices

1. Keep It Simple: Use for lightweight transformations only

2. Limit Dependencies: Best for 1-2 downstream models

3. Consider Debugging: Use sparingly to maintain query clarity

Ephemeral models are powerful for code organization but should be used judiciously. Consider views or tables for more complex or widely-used transformations.