Lookml Explore

Instructions

1. Core Standards

1. Naming Convention: snake_case for the Explore name.
2. Required Parameters:
   • description: 100% Coverage. Every Explore MUST have a description.
   • label: A user-friendly name for the Explore in the UI.
   • view_name: Defaults to explore name, but explicit definition is safer.
3. Joins:
   • relationship: Required (one_to_one, many_to_one).
   • sql_on: Required. Use ${left.id} = ${right.id} syntax.
   • type: defaults to left_outer. Use inner or full_outer explicitly if needed.
4. Formatting:
   • Do NOT use from to rename views just for aesthetics. Use view_label instead.
   • Exception: Polymorphic joins, Self-joins, Rescoping extensions.

2. Advanced Configuration

• always_filter: specific filters that users can change but cannot remove.
• sql_always_where: specific restrictions that users cannot change.
• persist_with: Link explore cache to datagroups (e.g., default_datagroup).
• fields: Use inclusive lists to strictly control content when necessary (ALL_FIELDS*, -view.field).

3. Performance Optimization (Aggregate Tables)

Aggregate Tables (Aggregate Awareness) allow Looker to query smaller, pre-aggregated tables instead of the raw granular data, drastically improving query performance.

Anatomy of an Aggregate Table

explore: orders {
  aggregate_table: rollup_name {
    query: {
      dimensions: [created_date, status]
      measures: [total_revenue, count]
      filters: [orders.created_date: "6 months"]
    }
    materialization: {
      datagroup_trigger: ecommerce_etl
      # partition_keys: ["created_date"] # BigQuery/Presto optimization
      # increment_key: "created_date"    # Incremental builds
      # increment_offset: 3              # Rebuild last 3 periods
    }
  }
}

Key Parameters

1. Query: Defines the "shape" of the rollup.

   • Dimensions: Include all dimensions commonly used in dashboards (including filters).
   • Measures: Include base measures (sum, count). Looker can derive averages from sum+count.
   • Filters: Optional. Restricts the rollup to a subset of data (e.g., "last 6 months").

2. Materialization:

   • datagroup_trigger: (Recommended) Rebuilds when the ETL job completes.
   • sql_trigger_value: Rebuilds when a SQL query returns a new value.
   • increment_key: (Advanced) Appends new data instead of full rebuilds. Best for massive tables.
   • indexes / partition_keys / cluster_keys: Dialect-specific optimizations.

3. Best Practices:

   • Timeframes: Include the finest grain needed (e.g., date). Looker can roll up date to month or year automatically.
   • Exact Match: The user's query must be a strict subset of the aggregate table's fields to satisfy the awareness logic.
   • Filter Awareness: If a user filters on a field not in the aggregate table, Looker cannot use it (unless it's an "exact match" special case). Add common filter fields to the dimensions list.

4. Extending Explores

• Extends: Use extends: [base_explore] to inherit joins, fields, and descriptions from another explore.
  • Use Case: Create a "Base" explore with common joins, then "Extended" explores for specific analysis (e.g., orders -> marketing_orders).

Examples

Basic Explore

explore: orders {
  label: "Orders"
  description: "Analyze order data, including user and product details."
  view_name: orders
  
  join: users {
    relationship: many_to_one
    sql_on: ${orders.user_id} = ${users.id} ;;
  }
}

Explore with Filters & Caching

explore: events {
  label: "Web Events"
  description: "User interaction events."
  persist_with: default_datagroup

  # Users can change this filter, but it defaults to '7 days'
  always_filter: {
    filters: [events.created_date: "7 days"]
  }

  # Users CANNOT change this filter.
  sql_always_where: ${events.is_test_data} = false ;;
  
  join: sessions {
    relationship: many_to_one
    sql_on: ${events.session_id} = ${sessions.session_id} ;;
  }
}

## Aggregate Table (Advanced)

```lookml
explore: orders {
  aggregate_table: monthly_sales_summary {
    query: {
      dimensions: [created_month, status, products.category]
      measures: [total_revenue, count]
      filters: [orders.created_date: "2 years"]
    }
    materialization: {
      datagroup_trigger: ecommerce_etl
      partition_keys: ["created_month"]
      increment_key: "created_month"
      increment_offset: 1 # Rebuild current and previous month
    }
  }
}

Extended Explore

explore: orders_extended {
  extends: [orders]
  label: "Orders (Marketing View)"
  view_name: orders
  
  # Add new joins specific to this view
  join: marketing_channels {
    sql_on: ${orders.channel_id} = ${marketing_channels.id} ;;
    relationship: many_to_one
  }
}

## Reference Skills

For more complex scenarios, refer to these specialized skills:
- [Advanced Explore Configuration](references/advanced.md): UNNESTing, lateral flattens, and row-level security.
- [Joins Deep Dive](references/joins.md): Detailed join types, relationships, and aliasing.