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post-1.0: add lag/lead window functions #182
Description
Roadmap source
ROADMAP.md: Phase 7.7a notes lag / lead were deferred to the post-1.0 backlog.
Work item
Add lag and lead support to Datalog window functions.
Acceptance criteria
- Parse
lagandleadwindow expressions. - Evaluate previous/next row values within each partition and ordering.
- Define behavior at partition boundaries.
- Add integration tests for partitioned and unpartitioned queries.
- Update Datalog docs and examples.
Activity
fix(api): revert QueryResult tuple variants for 1.x compat; add curre…
docs(roadmap): record v2.0 file-format policy and wave completion status
docs: bring TEST_COVERAGE.md fully current (998 tests)
adityamukho commentedon Oct 20, 2026
Moved to v3.1.0 (as ROADMAP/CLAUDE.md already list it), to be built after #551 so it exists only on the streaming engine, not on the executor that #551 deletes.
Depends on #547 (spec
docs/superpowers/specs/2026-10-20-aggregate-window-engine-design.md, merged in #640)::order-byvalue under one total value order (value_order, spec §3.1), then by the other:find-named variables, then input position (§4.1). Rows that tie on all of these are indistinguishable in the output, so row-based results are the same on every plan;:order-bygets the value at the last peer;Windowholds its whole sorted input (§6), so the work here is per-row evaluation only.For
lag/lead: the previous/next row is taken in that total order, within the partition; the partition boundary behaviour (default value ornil) still needs defining.Merge pull request #763 from project-minigraf/feat/182-lag-lead