Postgres plain-Ibis .all(...) calculated measures compile to unsupported FIRST(...)

[hachej]

Summary

PR 279 fixes the plain-Ibis/no-xorq YAML calculated_measures path for normal post-aggregation derived measures, but .all(...) percent-of-total calculated measures still fail on Postgres because BSL generates a FIRST(...) aggregate that Postgres does not provide.

Repro context

• BSL source: julien/plain-ibis-demo-window-pr278 / PR 279
• Commit tested: 2a226da (fix: resolve YAML calculated measures against measures first)
• Mode: plain Ibis, no xorq (HAS_XORQ=False)
• Ibis: 11.0.0
• Backend: Postgres

Minimal semantic YAML shape

target_phase_cells:
  table: target_phase_cells
  dimensions:
    phase: _.phase
  measures:
    target_cells: _.target_cells.sum()
  calculated_measures:
    pct_of_all_target_cells: _.target_cells / _.all(_.target_cells) * 100

Query

models["target_phase_cells"].query(
    dimensions=("phase",),
    measures=("pct_of_all_target_cells",),
).execute()

Actual result

psycopg.errors.UndefinedFunction: function first(bigint) does not exist
LINE 1: ... FIRST("t2"...
HINT: No function matches the given name and argument types. You might need to add explicit type casts.

Expected result

The .all(...) calculated measure should execute on Postgres, likely by compiling to a backend-supported window/subquery expression rather than FIRST(...), or by using a portable aggregate/window equivalent.

What does work in PR 279

Normal YAML calculated measures now work in the same plain-Ibis/Postgres setup, e.g.:

calculated_measures:
  coverage_ratio: _.scheduled_people / _.required_people
  avg_required_per_cell: _.required_people / _.target_cells
  scheduled_per_cell: _.scheduled_people / _.target_cells
  gap_ratio: _.coverage_gap / _.required_people

These all execute successfully against the mart layer.

Repro script location from local validation

In my local playground, this is captured as an expected failure in:

packages/core/bi/playground/scripts/test_bsl_healio_marts.py

The failing section is named:

target phase percent-of-total calculated measure (Postgres FIRST() gap)