gregfelice commented on issue #2443:
URL: https://github.com/apache/age/issues/2443#issuecomment-4773020845
**Correction — the root cause above is incomplete.** Verified by
instrumenting the transform and inspecting the generated plans; the real cause
is a missing correlation, not the `make_path_join_quals` early-return on its
own.
**What actually happens:** a single-node labeled pattern desugars to an
`EXISTS` sub-pattern. The inner vertex is *not* correlated to the outer
variable — it is handled like any vertex, and with no edge to carry a
correlation qual, the sub-pattern references nothing from the enclosing query.
The planner therefore produces an **uncorrelated one-time `InitPlan`** that is
true whenever any vertex of that label exists, independent of the outer row:
```
InitPlan 1
-> Result
One-Time Filter: ((InitPlan 1).col1)::agtype
```
Relationship patterns work precisely because the edge-driven join (`start_id
= a.id`) correlates them to the outer variable — confirmed by identical
node-level state in both cases but a correlated `SubPlan` only for the
relationship form.
So `make_path_join_quals` *is* the right place to fix, but the fix is to
**emit a correlated label filter**, not merely "add the label qual": for a
vertex-only pattern whose vertex has a non-default label and whose variable is
bound in an ancestor parse state, emit `_extract_label_id(<id>) = <label_id>`
via `make_qual` — whose name-based id reference resolves to the outer variable,
which both correlates the sub-pattern and enforces the label. After the fix the
plan is a correlated `SubPlan`:
```
SubPlan 1
-> Result
One-Time Filter: ((_extract_label_id(a_1.id))::integer = 3)
```
Fix + regression coverage in #2444. Note: `RETURN (a:Label)` in a
*projection* on an unlabeled bound variable is a separate, pre-existing
"multiple labels" guard, orthogonal to this issue and left unchanged.
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