Documentation

9. Views

Named, reusable query definitions stored on the database object.

What is a view?

A view is a named query stored on the database object. It is defined as a Python lambda (or any callable) that receives the db object and returns a Query. The query is re-executed every time you call db.view("name").to_list().

Views are not persisted to the .relpy.json file because they contain Python callables. Re-register views after loading a database from disk.

create_view

from relpy import RelPy, AutoNumber, col

db = RelPy()
# ... (table setup omitted for brevity)

db.create_view(
    "paid_orders",
    lambda db: (
        db.query("orders")
          .where(col("status") == "paid")
          .select("id", "amount", "user_id")
    ),
)

Using a view

# query the view like any table
rows = db.view("paid_orders").to_list()

# chain further operations
total = db.view("paid_orders").sum("amount")

# filter on top of the view
large_paid = (
    db.view("paid_orders")
      .where(col("amount") > 100)
      .to_list()
)

View management

Function	Returns	Description
`db.create_view(name, callable)`	`self`	Registers a named view.
`db.view(name)`	`Query`	Executes the view's callable and returns its `Query`.
`db.drop_view(name)`	`self`	Removes a view from the database.
`db.list_views()`	`list[str]`	Names of all registered views.
`db.describe_view(name)`	`dict`	Metadata for one view.
`db.describe_views()`	`list[dict]`	Metadata for all views.

View with join and aggregation

db.create_view(
    "revenue_by_city",
    lambda db: (
        db.query("orders")
          .join("users")
          .where(col("orders.status") == "paid")
          .group_by("users.city")
          .aggregate(
              orders=count(),
              revenue=sum_("orders.amount"),
          )
          .order_by("revenue", descending=True)
    ),
)

# Later in your code — re-execute without rewriting the query
summary = db.view("revenue_by_city").to_list()

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