Ephemeral Materialization

Describes dbt's ephemeral materialization, which integrates models as CTEs in dependent models, discussing advantages, disadvantages, and recommended use cases.

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.

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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

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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

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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') }}

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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.