Extended subqueries for Cypher #181
Description
CIR-2017-181
Support for subqueries increases the expressivity of query languages by a large margin.
This CIR seeks to improve Cypher to support a full set of relevant subqueries.
Background
Cypher today supports a limited set of subqueries
- List comprehensions
- Pattern predicates
- Existential subqueries
Use-Cases
Common uses for subqueries:
- Continuing after a set operation (e.g. UNION)
- Use of a scalar value (e.g. computed via aggregation) from deep within an expression
- Performing multiple updates based on additional matches without changing the cardinality of the outer query
Requirements
Make a proposal for adding full subquery support to Cypher, including:
- Correlated subqueries
- Uncorrelated subqueries
- Scalar subqueries in expressions
- Update subqueries (execute subquery without changing the outer query)
Considerations
- Interaction with existing features