D8 final GFQL compat-executor reachability audit and deletion/shrink decision #1466

Summary

Final coordinator/implementation lane for #1419 after the known compat-executor blockers have landed:

• D4 prep: native physical dispatch coverage needed to retire GFQL compat executor #1441 / Add native physical dispatch for planned GFQL routes #1448 native physical dispatch enabler
• D5 prep: inventory remaining compat executor fallbacks and CALL route decision #1455 / Route Cypher CALL through physical dispatch #1458 CALL native route
• D6 deletion prep: native route for simple top-level OPTIONAL MATCH fallback #1460 / Route simple OPTIONAL MATCH through native physical dispatch #1463 simple top-level OPTIONAL MATCH native route
• D7 deletion prep: native route for OPTIONAL MATCH reentry fallback #1461 / Route optional reentry through native planning #1462 optional reentry native route

The goal is to determine whether _execute_compiled_query_compat_non_union() and related compatibility wrappers/tests are still reachable, then either remove/shrink them or explicitly revise the #1419 2K LOC deletion target.

Goal

Get #1419 to a closeable state: either a real GFQL deletion PR with a fresh LOC receipt, or a recorded coordinator decision that the remaining safe deletion surface cannot meet the original >=2K LOC target.

Scope

• Re-audit _execute_compiled_query_compat_non_union() reachability on latest master.
• Enumerate all remaining callsites and classify each as:
  • unreachable/deletable,
  • still live but replaceable by native route,
  • public/deprecated compatibility API and excluded by GFQL deprecated validation API removal policy and release gate #1440,
  • feature-gap guard, not deletion debt.
• Identify stale wrappers, route shims, tests, fixtures, changelog/docs references, and TCK gates that can be deleted after D1-D7.
• If safe, implement the deletion/shrink PR.
• If not enough safe deletion remains, update [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419 with a de-scope/revise decision and close/reframe the deletion target.
• Recompute net GFQL LOC delta for [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419.
• Update [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419/Meta: benchmark coverage unlock plan for GFQL and GFQL/Cypher #992/Meta: GFQL compiler/planner post-M4 execution DAG (active wave) #1259 with receipts.

Out of scope

• Typed schema work (GFQL type system follow-on A: public declarative schema model + stable exports #1337/GFQL type system follow-on B: schema inference API + typed topology extraction #1338/GFQL type system follow-on C: public schema-Arrow APIs + plottable boundary enforcement #1339/GFQL remote: send bound typed GraphSchema with gfql_remote requests #1465/GFQL schema tutorial: infer, refine, bind, and validate Cypher #1464). That is a separate PR stack and should not consume this deletion lane.
• Deprecated public graphistry.compute.gfql.validate / graphistry.compute.gfql_validation removal; excluded by GFQL deprecated validation API removal policy and release gate #1440.
• New Cypher feature support unrelated to killing compatibility paths.
• tck-gfql residual sidecars Avoid setting variables in %%time blocks, and fix link at end #115 / match5-8 bookkeeping unless they directly block deletion.

Acceptance

• Reachability audit is recorded with file/callsite references.
• If code is deleted/shrunk: CI, tck-gfql, and relevant GFQL/cuDF validation are green.
• LOC receipt is posted against the [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419 deletion target.
• [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419 is either closed with the deletion receipt or explicitly revised/de-scoped with rationale.
• Meta: benchmark coverage unlock plan for GFQL and GFQL/Cypher #992 and Meta: GFQL compiler/planner post-M4 execution DAG (active wave) #1259 reflect the final [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419 state.

Related

• [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419
• Meta: benchmark coverage unlock plan for GFQL and GFQL/Cypher #992
• Meta: GFQL compiler/planner post-M4 execution DAG (active wave) #1259
• GFQL deprecated validation API removal policy and release gate #1440
• D4 prep: native physical dispatch coverage needed to retire GFQL compat executor #1441
• D5 prep: inventory remaining compat executor fallbacks and CALL route decision #1455
• D6 deletion prep: native route for simple top-level OPTIONAL MATCH fallback #1460
• D7 deletion prep: native route for OPTIONAL MATCH reentry fallback #1461