Suppression matches a record's own `name` field, so a projection that
filters on `name` without returning it carries an upstream value through.
The README claimed the record was always dropped on every query shape.
State the rule the code implements and pin the shape with a test.
`hasExtract` exempted only `in`. openvoxdb's `valid-operator?`
(src/puppetlabs/puppetdb/query_eng/engine.clj:2779-2784) lists `subquery`
separately, and the AST-rewrite stage (:2111-2123) expands
["subquery" entity expr] into ["in" cols ["extract" cols ["select_x" expr]]]
before any plan node is built, so its operand is projected into a subquery
exactly like `in`'s (:2705-2712). Exempt `subquery` and the explicit
`select_<entity>` forms (:1889-1911).
Signed-off-by: unkin-agent <unkin-agent@unkin.net>
- drop upstream facts of the configured name whenever the feature is enabled,
independent of the per-query injection gate, and log the drop once per request
- walk the whole AST for a nested extract and skip injection when one is found
outside an in subquery
- skip the environment scan on /facts when nothing is injected
- document the override rule and that PQL-syntax queries never get the fact
## Why
With several PuppetDBs behind one endpoint, consumers cannot tell which backend a node's data came from.
## How
- Add a synthetic `pdbmux_source` fact per certname on `/facts`, valued with the backend that won the facts merge, and stamp the same key on merged `/nodes` records.
- Emit all four fact keys including `environment`, which clients index directly.
- Skip injection for top-level `extract` queries, so `count()` and other aggregates keep the backends' own numbers, and for `/facts` queries constraining `name`; a `name` filter inside an `in` subquery still injects.
- Replace, never duplicate, an upstream fact of the configured name.
- Configure via `source_fact` / `source_fact_enabled` (`PDBMUX_SOURCE_FACT`, `PDBMUX_SOURCE_FACT_ENABLED`), defaulting to `pdbmux_source` enabled.
unkin-agent