LogQL Binary Operations and Vector Matching

[frisbeeman]

Overview

Implement LogQL binary operations between vectors, including arithmetic, comparison, and logical operators with vector matching modifiers.

Parent Issue

Part of #6 (Query Service Implementation), delegated from #8 (LogQL Query Compiler).

Context

Binary operations allow combining two vector expressions. Currently, all binary operations return NotImplemented error. Only scalar literals work in simple contexts.

Requirements

Arithmetic Operators

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulo
^	Exponentiation

Comparison Operators

Operator	Description
==	Equal (filter or bool)
!=	Not equal
>	Greater than
>=	Greater or equal
<	Less than
<=	Less or equal

Logical/Set Operators

Operator	Description
and	Intersection
or	Union
unless	Difference

Vector Matching Modifiers

Modifier	Description
on(labels...)	Match only on specified labels
ignoring(labels...)	Ignore specified labels when matching
group_left(labels...)	Many-to-one matching
group_right(labels...)	One-to-many matching

Example Queries

rate({job="app"}[5m]) * 60
rate({job="app"}[5m]) / rate({job="db"}[5m])
rate({job="app"}[5m]) > 100
sum by (service) (rate({job="app"}[5m])) / on(service) sum by (service) (rate({job="db"}[5m]))
vector1 and vector2
vector1 unless vector2

Implementation Approach

1. Implement binary expression planning in planner.rs:

   • Handle BinOpExpr in query planning
   • Support vector-scalar and vector-vector operations

2. Vector matching logic:

   • Default: match on all labels
   • on(): JOIN on specified labels only
   • ignoring(): JOIN on all labels except specified
   • group_left/right: handle one-to-many relationships

3. Translation to DataFusion:

   • Arithmetic: col("left.value") + col("right.value")
   • Comparison: filter() or CASE WHEN for bool modifier
   • Logical: INNER/LEFT/ANTI JOINs on label columns

Acceptance Criteria

• All arithmetic operators work between vectors and scalars
• Comparison operators filter or return 0/1 with bool modifier
• Logical operators perform correct set operations
• on() and ignoring() modifiers work correctly
• group_left() and group_right() handle cardinality correctly
• Proper error messages for cardinality violations
• Unit tests for each operator
• Integration tests with complex expressions

Technical References

• LogQL Binary Operations
• Vector Matching
• Technical spec: src/query/logql/TECHNICAL_SPEC.md Section 6