docs(g2): increment 1 located -- regions are discovered whole-repo, never change-scoped

The 4095 candidates are not an in-scan artifact: push/runner.py:345 discovers
head_regions across the whole head tree, then runner.py:397 passes them wholesale
to scan_repository with change_context threaded in but unused for scoping. The
scan enumerates all regions x families (scan.py:167/364) and, with
order_by_evidence=True, evidence-tiers every pair before analysis -> the ~236s
from increment 0 -> deadline at query_seconds=0.

Fix locus (increment 2): scope the analyzed region set to context.changed_paths +
dataflow neighbourhood (regions.py:279 primitive exists; compare_targeted_base is
precedent). Keep the CPG whole-repo so taint can trace into the change from
unchanged code; only the question set is change-scoped.

Co-Authored-By: Claude Opus 4.8 <[email protected]>
This commit is contained in:
Marius Ciepluch
2026-10-11 11:24:43 +02:00
co-authored by Claude Opus 4.8
parent 7a1e47e0cc
commit 9580ad1e30
@@ -44,8 +44,20 @@ detection is being lost, not in Joern's capability.
the budget was spent before a single query ran. The CPG build is NOT the bottleneck; the over-broad candidate set
is. Change-scoping is confirmed as the right lever, and because per-candidate prep includes the line-correspondence
work, fewer candidates also cuts that cost (the two fixes compound).
- [ ] **1. Locate the exact selection/budget code** in `rank.py`/`mapping.py` that marks candidates
`selected` vs `deferred:deadline_exhausted`.
- [x] **1. Located (2026-10-11).** The over-enumeration is upstream of the scan, not inside it:
- `push/runner.py:345-348` — `head_regions = discovery(tip.root, …)` discovers regions across the **whole head
tree** (the ~4,095), independent of the change.
- `push/runner.py:397-407` — those regions are passed wholesale to `scan_repository(..., change_context=context)`;
`change_context` is threaded in but **never scopes the region set**.
- `model/scan.py:167` and `:364` — `[_identity(unit, r, f) for r in regions for f in r.families]` enumerates all
regions × families; with `order_by_evidence=True` (`runner.py:288/403`) the scan evidence-tiers **every** pair
before analysis — that pre-work is the ~236 s measured in increment 0, so the deadline hits at `query_seconds=0`.
- Primitive already present: `model/regions.py:279` computes the changed-path set from the context;
`compare_targeted_base` (`runner.py:411`) is a precedent for change-targeted work.
- **Fix locus (increment 2):** restrict the *analyzed* region set to the change's declarations + dataflow
neighbourhood (filter `head_regions` by `context.changed_paths` before the scan, or scope the enumeration inside
`scan_repository`). Keep the **CPG whole-repo** so taint queries can still trace sources from unchanged code into
the changed regions — only the question set is change-scoped.
- [ ] **2. Seed analysis from the change.** Prioritize (or restrict first-pass to) the changed declarations plus
their call/data neighborhood over repo-wide static rank, within budget.
- [ ] **3. Soundness.** Keep cross-file dataflow INTO the changed function (don't scope to literal changed lines);