Title: Implement MergeSumToVectorSum optimizer rule for merging many SUM aggregations
Title: Implement MergeSumToVectorSum optimizer rule for merging many SUM aggregations: a task in LegoFlow-SWE (Harbor dataset). Context Queries that compute many SUM(…) aggregates over different columns of the same type (e.g., hundreds of REAL or BIGINT columns) currently execute each aggregation…
The task
**Context** Queries that compute many `SUM(…)` aggregates over different columns of the same type (e.g., hundreds of `REAL` or `BIGINT` columns) currently execute each aggregation independently. This leads to redundant scans and inefficient execution, especially when the number of SUMs grows large.
Part of Lego-X/LegoFlow-SWE.