rill-metrics-view

# Instructions for developing a metrics view in Rill ## Introduction Metrics views are resources that define queryable business metrics on top of a table in an OLAP database. They implement what other business intelligence tools call a "semantic layer" or "metrics layer". Metrics views are lightweight resources that only perform validation when reconciled. They are typically found downstream of connectors and models in the project's DAG. They power many user-facing features: - **Explore dashboards**: Interactive drill-down interfaces for data exploration - **Canvas dashboards**: Custom chart and table components - **Alerts**: Notifications when data meets certain criteria - **Reports**: Scheduled data exports and summaries - **Custom APIs**: Programmatic access to metrics ## Core Concepts ### Table source The `model:` property specifies the underlying table that powers the metrics view. It can reference: 1. **A model in the project**: Just use the model name (e.g., `model: events`) 2. **An external table**: Specify the table name as it exists in the OLAP connector ```yaml # Referencing a model in the project model: events # Referencing an external table (connector defaults to project's default OLAP) connector: clickhouse # Optional: specify if different from default model: my_external_table # Note: Doesn't support dot syntax for database/schema name. Use the separate `database:` or `database_schema:` keys for that if relevant (but try without first and see if that works). ``` **Note**: The `table:` property is a legacy alias for referencing external tables. Always prefer `model:` in new metrics views. ### Timeseries The `timeseries:` property identifies the timestamp column used for time-based filtering and line charts. This column must be a time/timestamp type in the underlying table. ```yaml timeseries: event_time ``` If the timeseries column is not listed in `dimensions:`, Rill automatically adds it as a time dimension. You can optionally configure additional time-related settings: ```yaml timeseries: event_time smallest_time_grain: hour # Minimum granularity users can select first_day_of_week: 7 # Sunday (1=Monday, 7=Sunday) first_month_of_year: 4 # April (fiscal year starting in April) ``` It is _strongly_ recommended that you add a primary timeseries to every metrics view you create (it makes for a much better dashboard experience). ### Dimensions Dimensions are attributes you can group by or filter on. They are typically categorical (strings, enums) or temporal (dates, timestamps). Rill infers the dimension type from the underlying SQL data type: - **Categorical**: String, enum, boolean columns - **Time**: Timestamp, date, datetime columns - **Geospatial**: Geometry or geography columns Define dimensions using either a direct column reference or a SQL expression: ```yaml dimensions: # Simple column reference - name: country column: country # Computed expression - name: device_category expression: CASE WHEN device_type IN ('phone', 'tablet') THEN 'Mobile' ELSE 'Desktop' END # With display name and description - name: campaign_name display_name: Campaign description: Marketing campaign that drove the traffic column: campaign_name ``` **Naming**: Each dimension needs a `name` (stable identifier used in APIs and references), which defaults to `column:` if provided. The `display_name:` is optional, and defaults to a humanized version of `name` if not specified. ### Measures Measures are aggregation expressions that compute numeric values when grouped by dimensions. They must use aggregate functions like `SUM()`, `COUNT()`, `AVG()`, `MIN()`, `MAX()`. ```yaml measures: - name: total_revenue display_name: Total Revenue expression: SUM(revenue) description: Sum of all revenue in USD format_preset: currency_usd - name: unique_users display_name: Unique Users expression: COUNT(DISTINCT user_id) format_preset: humanize - name: conversion_rate display_name: Conversion Rate expression: SUM(conversions) / NULLIF(SUM(visits), 0) format_preset: percentage valid_percent_of_total: false # Disable % of total for ratios ``` **Format presets**: Control how values are displayed: - `none`: Raw number - `humanize`: Round to K, M, B (e.g., 1.2M) - `currency_usd`: Dollar format with 2 decimals ($1,234.56) - `currency_eur`: Euro format - `percentage`: Multiply by 100 and add % sign - `interval_ms`: Convert milliseconds to human-readable duration For custom formatting, use `format_d3` with a [d3-format](https://d3js.org/d3-format) string: ```yaml format_d3: "$,.2f" # $1,234.56 format_d3: ".1%" # 12.3% format_d3: ",.0f" # 1,235 (rounded, with thousands separator) ``` ### Best practices for dimensions and measures **Naming conventions:** - Use `snake_case` for the `name` field (e.g., `total_revenue`, `unique_users`) - Only add `display_name` and `description` if they provide meaningful context beyond what `name` conveys (display names auto-humanize from the name by default) - Ensure measure names don't collide with column names in the underlying table **Getting started with measures:** - Start with a `COUNT(*)` measure as a baseline (e.g., `total_records` or `total_events`) - Add `SUM()` measures for numeric columns that represent quantities or values - Use `humanize` as the default format preset unless the data has a specific format requirement - Keep initial measures simple using only `COUNT`, `SUM`, `AVG`, `MIN`, `MAX` aggregations - Add more complex expressions (ratios, conditional aggregations) only when needed **Dimension selection:** - Include all categorical columns (strings, enums, booleans) that users might want to filter or group by - Start with 5-10 dimensions; add more based on user needs **Timeseries:** - If there is any date/timestamp column in the underlying table, pick the primary or most interesting one and add it under `dimensions:` - It is also _strongly_ recommended that you configure a primary time dimension using `timeseries:` ### Auto-generated explore When you create a metrics view, Rill automatically generates an explore dashboard with the same name, exposing all dimensions and measures. To customize the explore (you usually should not need to), add an `explore:` block: ```yaml explore: display_name: Sales Dashboard defaults: time_range: P7D measures: - total_revenue - order_count ``` **Legacy behavior**: Files with `version: 1` do NOT auto-generate an explore. Omit `version:` in new metrics views to get the auto-generated explore. ## Full Example Here is a complete, annotated metrics view: ```yaml # metrics/orders.yaml type: metrics_view # Display metadata display_name: Orders Analytics description: Analyze order performance by various dimensions # Data source - references the 'orders' model in the project model: orders # Time column for time-series charts and filtering timeseries: order_date smallest_time_grain: day # Dimensions for grouping and filtering dimensions: - name: order_date display_name: Order Date column: order_date - name: country display_name: Country column: shipping_country - name: product_category display_name: Product Category column: category description: High-level product grouping - name: customer_segment display_name: Customer Segment expression: | CASE WHEN lifetime_value > 1000 THEN 'High Value' WHEN lifetime_value > 100 THEN 'Medium Value' ELSE 'Low Value' END - name: is_repeat_customer display_name: Repeat Customer expression: CASE WHEN order_number > 1 THEN 'Yes' ELSE 'No' END # Measures for aggregation measures: - name: total_orders display_name: Total Orders expression: COUNT(*) format_preset: humanize - name: total_revenue display_name: Total Revenue expression: SUM(order_total) format_preset: currency_usd description: Gross revenue before refunds - name: average_order_value display_name: Avg Order Value expression: SUM(order_total) / NULLIF(COUNT(*), 0) format_preset: currency_usd valid_percent_of_total: false - name: unique_customers display_name: Unique Customers expression: COUNT(DISTINCT customer_id) format_preset: humanize - name: items_per_order display_name: Items per Order expression: SUM(item_count) / NULLIF(COUNT(*), 0) format_d3: ",.1f" valid_percent_of_total: false ``` ## Security Policies Security policies control who can access a metrics view and what data they can see. This is a powerful feature for multi-tenant dashboards and role-based access control. ### Basic access control The `access:` property controls whether users can view the metrics view at all: ```yaml security: # Allow access for everyone access: true # Deny access for everyone (useful for draft dashboards) access: false # Conditional access based on user attributes access: "'{{ .user.admin }}' = 'true'" ``` The expression syntax should be a DuckDB expression, which will be evaluated in a sandbox without access to any tables. ### Row-level security The `row_filter:` property restricts which rows a user can see. It's a SQL expression that references user attributes via templating: ```yaml security: access: true row_filter: domain = '{{ .user.domain }}' ``` Common user attributes: - `{{ .user.email }}`: User's email address - `{{ .user.domain }}`: Email domain (e.g., "acme.com") - `{{ .user.admin }}`: Boolean admin flag - Custom attributes configured in Rill Cloud The row filter should use the SQL syntax of the metrics view's model, and can reference other tables in the model's connector. ### Complex row filters Use logical operators for sophisticated access patterns: ```yaml security: access: true row_filter: > {{ .user.admin }} OR '{{ .user.domain }}' = 'acme.com' {{ if hasKey .user "tenant_id" }} OR tenant_id = '{{ .user.tenant_id }}' {{ end }} ``` ### Hiding dimensions and measures The `exclude:` property conditionally hides specific dimensions or measures from certain users: ```yaml security: access: true exclude: - if: "NOT {{ .user.admin }}" names: - cost_per_acquisition # Hide sensitive cost data from non-admins - internal_notes ``` ## Advanced Features ### Annotations Annotations overlay contextual information (like events or milestones) on time-series charts: ```yaml annotations: - name: product_launches model: product_launches # Must have 'time' and 'description' columns measures: - total_revenue # Only show on these measures # Optional columns in annotation model: # - time_end: For range annotations # - grain: Show only at specific time grains (day, week, etc.) ``` ### Unnest for array dimensions When a column contains arrays, use `unnest: true` to flatten it at query time: ```yaml dimensions: - name: tags display_name: Tags column: tags unnest: true # Allows filtering by individual array elements ``` ### Cache configuration Configure caching for slow metrics views that use external tables: ```yaml cache: enabled: true key_ttl: 5m key_sql: SELECT MAX(updated_at) FROM orders ``` You should not add a `cache:` config when the metrics view references a model inside the project since Rill does automatic cache management in that case. ## Dialect-Specific Notes SQL expressions in dimensions and measures use the underlying OLAP database's dialect. ### DuckDB DuckDB is the default OLAP engine for local development. **Conditional aggregation with FILTER**: ```yaml # DuckDB supports FILTER clause for conditional aggregation expression: COUNT(*) FILTER (WHERE status = 'completed') ``` ### ClickHouse ClickHouse is recommended for production workloads with large datasets. **Conditional aggregation**: ```yaml # ClickHouse uses IF or CASE inside aggregations expression: countIf(status = 'completed') expression: sumIf(revenue, status = 'completed') ``` **Date functions**: ```yaml expression: toYear(order_date) expression: toStartOfMonth(order_date) expression: toYYYYMMDD(order_date) ``` **Array functions**: ```yaml expression: arrayJoin(tags) # Unnest arrays ``` ### Druid **Approximate distinct counts**: ```yaml expression: APPROX_COUNT_DISTINCT_DS_HLL(user_id) ``` ## Reference documentation Here is a full JSON schema for the metrics view syntax: ``` allOf: - properties: ai_instructions: description: Extra instructions for [AI agents](/guide/ai/mcp). Used to guide natural language question answering and routing. type: string annotations: description: Used to define annotations that can be displayed on charts items: properties: connector: description: Refers to the connector to use for the annotation type: string database: description: Refers to the database to use in the OLAP engine (to be used in conjunction with table). Otherwise, will use the default database or schema if not specified type: string database_schema: description: Refers to the schema to use in the OLAP engine (to be used in conjunction with table). Otherwise, will use the default database or schema if not specified type: string measures: $ref: '#/definitions/field_selector_properties' description: Specifies which measures to apply the annotation to. Applies to all measures if not specified model: description: Refers to the model powering the annotation (either table or model is required). The model must have 'time' and 'description' columns. Optional columns include 'time_end' for range annotations and 'grain' to specify when the annotation should appear based on dashboard grain level. type: string name: description: A stable identifier for the annotation. Defaults to model or table names when not specified type: string table: description: Refers to the table powering the annotation, should be used instead of model for annotations from external OLAP tables (either table or model is required) type: string type: object type: array connector: description: Refers to the connector type for the metrics view, see [OLAP engines](/developers/build/connectors/olap) for more information type: string database: description: Refers to the database to use in the OLAP engine (to be used in conjunction with table). Otherwise, will use the default database or schema if not specified type: string database_schema: description: Refers to the schema to use in the OLAP engine (to be used in conjunction with table). Otherwise, will use the default database or schema if not specified type: string description: description: Refers to the description for the metrics view type: string dimensions: description: Relates to exploring segments or dimensions of your data and filtering the dashboard items: anyOf: - required: - column - required: - expression properties: column: description: a categorical column type: string description: description: a freeform text description of the dimension type: string display_name: description: a display name for your dimension type: string expression: description: a non-aggregate expression such as string_split(domain, '.'). One of column and expression is required but cannot have both at the same time type: string lookup_default_expression: description: an optional SQL expression used as a fallback value when no match is found in the dictionary (maps to `dictGetOrDefault`) type: string lookup_key_column: description: the primary key column in the lookup dictionary that corresponds to the dimension's `column` in the fact table type: string lookup_table: description: the name of a ClickHouse dictionary to use for query-time lookups. Use `database.dictionary_name` for dictionaries in a non-default database. All three `lookup_*` fields (`lookup_table`, `lookup_key_column`, `lookup_value_column`) must be specified together. See [Query-Time Joins](/developers/build/metrics-view/dimensions/lookup) for details type: string lookup_value_column: description: the attribute column in the lookup dictionary whose values will be displayed for this dimension type: string name: description: a stable identifier for the dimension type: string tags: description: optional list of tags for categorizing the dimension (defaults to empty) items: type: string type: array type: description: 'Dimension type: "geo" for geospatial dimensions, "time" for time dimensions or "categorical" for categorial dimensions. Default is undefined and the type will be inferred instead' type: string unnest: description: if true, allows multi-valued dimension to be unnested (such as lists) and filters will automatically switch to "contains" instead of exact match type: boolean uri: description: enable if your dimension is a clickable URL to enable single click navigation (boolean or valid SQL expression) type: - string - boolean type: object type: array display_name: description: Refers to the display name for the metrics view type: string explore: $ref: '#/definitions/explore_properties' description: Defines an optional inline explore view for the metrics view. If not specified a default explore will be emitted unless `skip` is set to true. required: - type first_day_of_week: