migrate-from-cube

name	migrate-from-cube
description	Migrate a Cube.js semantic layer to airlayer .view.yml files. Use when the user has existing Cube.js schema files (.js or .yml) they want to convert to airlayer format.

Migrate from Cube.js

You are converting Cube.js schema files into airlayer .view.yml files. Each Cube.js cube becomes one .view.yml file.

Step 1: Identify the schema files

Cube.js schemas can be in two formats. Read all the cube files and identify which format they use:

JavaScript format (.js files in schema/ or model/cubes/):

cube(`orders`, {
  sql_table: `public.orders`,
  dimensions: { ... },
  measures: { ... },
  joins: { ... },
})

YAML format (.yml files in model/cubes/):

cubes:
  - name: orders
    sql_table: public.orders
    dimensions: ...
    measures: ...
    joins: ...

YAML vs JS naming: Cube.js YAML uses camelCase measure types (countDistinct, countDistinctApprox, avg) while JS uses snake_case (count_distinct, avg). Both mean the same thing — map them identically.

Read ALL cube files before starting to write any .view.yml — you need the full picture to correctly translate joins into entity pairs.

Step 2: Plan entity translations

Joins are the most important thing to get right. airlayer uses entities on both sides of a join — the entity name must match on both views for airlayer to auto-generate the JOIN.

For each join in the Cube.js schema, parse the join SQL to find the FK and PK columns:

Cube.js join (declared on the FK side / "owning" cube):

joins: {
  customers: {
    relationship: `many_to_one`,
    sql: `${CUBE}.customer_id = ${customers}.id`,
  },
},

Translation:

• The LHS column (customer_id) → foreign entity on orders
• The RHS column (id) → primary entity on customers
• Pick a shared entity name based on the concept: use the joined cube name (customer)

# orders.view.yml
entities:
  - name: customer
    type: foreign
    key: customer_id

# customers.view.yml
entities:
  - name: customer
    type: primary
    key: id

Entity naming rules:

• Use the joined cube name as the entity name (e.g., join to customers → entity name customer)
• For one_to_many joins (the owning side has the PK): entity is primary on the owning cube, foreign on the target
• For many_to_one joins (the owning side has the FK): entity is foreign on the owning cube, primary on the target
• Entity names MUST match exactly across views — customer ≠ Customer
• A cube can have multiple entity declarations (one per relationship)

Critical: key/keys must reference dimension names, not column names.

airlayer validates that entity keys match the name: of a dimension in the same view — NOT the raw column name in expr:. If your dimension is named store_id with expr: Store, the entity key must be store_id, not Store.

# WRONG — 'Store' is a column name, not a dimension name
entities:
  - name: store
    type: primary
    keys: ["Store", "Date"]       # ✗ validator error

# CORRECT — use the dimension names defined in the same view
entities:
  - name: store
    type: primary
    keys: ["store_id", "week_date"]   # ✓ matches dimension name fields

# For single-column keys, use key: (not keys:)
entities:
  - name: store
    type: primary
    key: store_id                 # ✓

Build a table mapping (cube_name, entity_name) → (type, key) for all joins before writing any files.

Step 3: Translate each cube

For each cube, create a .view.yml file in the project directory.

Table name

sql_table: `public.orders`   →   table: public.orders
sql: `SELECT * FROM orders WHERE active = true`  →  table: "(SELECT * FROM orders WHERE active = true)"

For cubes using sql: (a subquery), wrap the value in quotes as the table: value.

Dimensions

Type mapping:

Cube.js type	airlayer type	Notes
string	string
number	number
boolean	boolean
time	date	Use datetime only if the column includes a time component (e.g., timestamps)
geo	string	Note the approximation in a comment

Expression rewriting:

• sql: \column_name`→expr: column_name`
• sql: \${CUBE}.column_name`→expr: column_name(strip${CUBE}.`)
• sql: \${CUBE}.qty * ${CUBE}.price`→expr: "qty * price"(strip all${CUBE}.` prefixes)
• sql: \${OtherCube}.column`→ **cannot go inexpr`** directly; see cross-view references below

Primary key dimensions:

• Dimensions with primary_key: true → declare as a dimension AND add a primary entity
• Keep the dimension itself (for grouping/filtering), but also add the entity declaration

Example — JS:

dimensions: {
  order_id: { sql: `id`, type: `number`, primary_key: true },
  status:   { sql: `status`, type: `string` },
  created_at: { sql: `created_at`, type: `time` },
  line_total: { sql: `${CUBE}.qty * ${CUBE}.unit_price`, type: `number` },
}

→ YAML:

entities:
  - name: order
    type: primary
    key: id

dimensions:
  - name: order_id
    type: number
    expr: id

  - name: status
    type: string
    expr: status

  - name: created_at
    type: datetime
    expr: created_at

  - name: line_total
    type: number
    expr: "qty * unit_price"

Measures

Type mapping:

Cube.js type	airlayer type	Notes
count	count	No expr needed
count_distinct	count_distinct
count_distinct_approx	count_distinct	Becomes exact; note the change
sum	sum
avg	average	Cube.js uses avg, airlayer uses average
min	min
max	max
number	number	Computed/derived — use expr with the formula (see note below)
running_total	(no equivalent)	Use the cumulative motif at query time instead

number vs custom — picking the right type:

• Use type: number when the expression contains row-level math (no aggregate function) and airlayer wraps it: expr: "qty * unit_price"
• Use type: custom when the expression is already a full aggregation and should be passed through verbatim: VARIANCE(Weekly_Sales), CORR(Temperature, Sales), STDDEV(x) / AVG(x) * 100

# number — row-level formula, airlayer adds no wrapper
- name: profit_margin
  type: number
  expr: "total_profit / NULLIF(total_revenue, 0)"

# custom — expression already contains its own aggregate function(s)
- name: sales_stddev
  type: custom
  expr: "STDDEV(Weekly_Sales)"

- name: temp_correlation
  type: custom
  expr: "CORR(Temperature, Weekly_Sales)"

Measure filters:

completed_count: {
  type: `count`,
  filters: [{ sql: `${CUBE}.status = 'completed'` }],
}

→

- name: completed_count
  type: count
  filters:
    - expr: "status = 'completed'"

Filter expression rewriting rules:

• ${CUBE}.column = 'value' → strip ${CUBE}. → column = 'value'
• column = 'value' (no ${CUBE}. prefix) → use as-is → column = 'value'
• Both forms appear in Cube.js YAML schemas; bare column references need no change.

Derived measures (type: number):

profit_margin: {
  sql: `${total_profit} / NULLIF(${total_revenue}, 0)`,
  type: `number`,
}

→

- name: profit_margin
  type: number
  expr: "total_profit / NULLIF(total_revenue, 0)"

Replace ${measure_name} references with the measure name directly (airlayer resolves measure refs by name).

Segments

segments: {
  completed: { sql: `${CUBE}.status = 'completed'` },
  high_value: { sql: `${CUBE}.amount > 1000` },
}

→

segments:
  - name: completed
    expr: "status = 'completed'"

  - name: high_value
    expr: "amount > 1000"

Step 4: Handle cross-view references

When a dimension sql references another cube — ${OtherCube}.column — it's a subquery dimension. Use sub_query: true:

// In customers cube
total_orders: {
  sql: `${orders.count}`,
  type: `number`,
  sub_query: true,
}

→

- name: total_orders
  type: number
  expr: "orders.order_count"
  sub_query: true

The expr for a sub_query dimension is view_name.measure_name referencing the measure from the related view.

Step 5: Required view fields

Every .view.yml must have:

name: <cube_name> # snake_case
table: <sql_table value> # actual DB table/schema.table

Optional but recommended:

description: "..." # from cube's title/description field if present
dialect: postgres # match the database type
datasource: warehouse # match the database name from config.yml

Step 6: Validate

After writing all .view.yml files, validate them:

airlayer validate

Fix any errors reported. Common issues:

• Entity name mismatch across views (must be identical strings)
• Missing expr on a measure that requires one
• Invalid type value

Step 7: Test joins

For any views connected by entities, test a cross-view query to confirm joins work:

airlayer query \
  --dimension customers.name \
  --measure orders.total_revenue

If the join fails, check that entity names match exactly across both views.

What doesn't translate

The following Cube.js features have no equivalent in airlayer. Skip them during migration:

Cube.js feature	Action
pre_aggregations	Skip — airlayer has no caching layer
refresh_key	Skip — caching directive
rolling_window on measures	Use moving_average or cumulative motif at query time
access_policy / public: false	Skip — airlayer has no row-level security
data_source override per cube	Set datasource: at the view level instead
extends (cube inheritance)	Inline the inherited fields manually
shown: false on members	Skip — airlayer shows all members

Full example

Input (orders.js):

cube(`orders`, {
  sql_table: `orders`,
  joins: {
    customers: {
      relationship: `many_to_one`,
      sql: `${CUBE}.customer_id = ${customers}.id`,
    },
  },
  dimensions: {
    order_id: { sql: `id`, type: `number`, primary_key: true },
    status: { sql: `status`, type: `string` },
    created_at: { sql: `created_at`, type: `time` },
  },
  measures: {
    count: { type: `count` },
    total_revenue: { sql: `amount`, type: `sum` },
    avg_order_value: { sql: `amount`, type: `avg` },
    completed_count: {
      type: `count`,
      filters: [{ sql: `${CUBE}.status = 'completed'` }],
    },
  },
});

Output (orders.view.yml):

name: orders
table: orders

entities:
  - name: order
    type: primary
    key: id
  - name: customer
    type: foreign
    key: customer_id

dimensions:
  - name: order_id
    type: number
    expr: id

  - name: status
    type: string
    expr: status

  - name: created_at
    type: datetime
    expr: created_at

measures:
  - name: count
    type: count

  - name: total_revenue
    type: sum
    expr: amount

  - name: avg_order_value
    type: average
    expr: amount

  - name: completed_count
    type: count
    filters:
      - expr: "status = 'completed'"

Output (customers.view.yml):

name: customers
table: customers

entities:
  - name: customer
    type: primary
    key: id

dimensions:
  - name: id
    type: number
    expr: id
  # ... other dimensions