Metaissue: M4 wave-1 execution DAG (pass framework + predicate pushdown safety primitives)

[lmeyerov]

Goal alignment

Start M4 with an execution shape that matches current landed M3 reality (incremental cutover, compatibility-preserving), while preserving the original M4 intent:

• introduce composable pass framework over LogicalPlan
• establish correctness/safety primitives for predicate pushdown
• prepare for PredicatePushdownPass implementation lane immediately after wave-1

Spec source: plans/compiler-refactor/milestone-M4.md

Why this meta now

M3 follow-ups #1168 and #1169 are closed. Next work should move to M4.

Wave-1 lanes (parallel)

• M4-PR1: pass framework skeleton + pipeline hook + verifier guard #1180 M4-PR1 pass framework skeleton + pipeline hook + verify-after-pass
• M4-PR2: predicate pushdown safety primitives (ScopeFrame barrier + null-safe classifier) #1181 M4-PR2 predicate pushdown safety primitives (ScopeFrame barrier + null-safety classifier + focused tests)

Follow-on lane

• M4-PR3: implement PredicatePushdownPass rewrite using pass framework + safety primitives #1187 M4-PR3 PredicatePushdownPass rewrite via pass framework + safety primitives

DAG

1. Run #1180 and #1181 in parallel.
2. Merge in either order if truly disjoint and green.
3. Open M4-PR3 for actual PredicatePushdownPass rewrite logic once #1180 + #1181 are merged.

Conformance gate for wave-1

• Pass framework is pure, explicit, and verifier-guarded.
• Predicate safety primitives are independently tested and reusable.
• No silent semantic change in OPTIONAL MATCH behavior.
• CI green.

Notes

• If M4 spec text still assumes hard M3 conditions that are now incremental/deferred, track that drift explicitly in issue comments and keep implementation requirements concrete in child issues.

Completion

• Wave-1 prerequisites (#1180, #1181) landed.
• Follow-on rewrite lane (#1187) landed.
• Closing this meta as completed.

[lmeyerov]

Status update after merge of #1182:

• Marked M4-PR1: pass framework skeleton + pipeline hook + verifier guard #1180 complete in the wave-1 checklist.
• Remaining open lane for wave-1: M4-PR2: predicate pushdown safety primitives (ScopeFrame barrier + null-safe classifier) #1181.
• Metaissue stays open until M4-PR2: predicate pushdown safety primitives (ScopeFrame barrier + null-safe classifier) #1181 lands.

[lmeyerov]

Closed #1183 (squash bf95091a, 2026-04-22) — #1181 merged. Both wave-1 lanes (#1180, #1181) are now merged. Wave-1 complete; ready to open M4-PR3 for PredicatePushdownPass.

[lmeyerov]

Opened M4-PR3 execution issue: #1187 (PredicatePushdownPass rewrite).\n\nWave-1 prerequisites are complete (#1180/#1181). Next critical path is #1187.

[lmeyerov]

Tracking update from M3 follow-up lane:

• M3 follow-up: decouple gfql_remote Cypher string path from deprecated compile_cypher surface #1185 is now complete via fix(gfql): decouple gfql_remote Cypher string path from deprecated compile_cypher #1186 (merged April 22, 2026).

This removes remote string-path coupling to deprecated compile_cypher() while preserving remote wire behavior, reducing pre-M4 lifecycle debt.

[lmeyerov]

Opened successor execution lane for post-PR3 M4 work: #1189 (two-tier pass execution semantics: Tier 1 structural + Tier 2 fixed-point loop).

[lmeyerov]

Schedule update: added deferred follow-on #1190 (scope-aware WITH/ScopeFrame barrier enforcement for predicate pushdown) based on PR #1188 review. Execution order: #1187 -> #1189 -> #1190.

[lmeyerov]

Meta completion update:

• #1180 and #1181 were already complete.
• #1187 has now landed via GFQL: implement predicate pushdown pass rewrite (#1187) #1188.
• Closing this metaissue as completed.

[lmeyerov]

Post-meta follow-up landed: #1190 is complete via merged PR #1192: #1192

This closes the deferred scope-aware barrier plumbing follow-up after M4-PR3 by adding real pass-time scope metadata threading and barrier enforcement tests.