DEV-1566: pg-facade — CAST(<column> AS <type>) in projection

[ZmeiGorynych]

Summary

• Pattern-match CAST(<column> AS <type>) (and col::type sugar) in the shared facade translator; the engine still executes the bare column and the wire OID is overridden via projection_types. Strict per-pair coercion allowlist gates which (source, target) combos round-trip cleanly.
• Wire encoder fixes in slayer/pg_facade/types.py: OID_TIMESTAMP + dt.date widening (text-format DATE→TIMESTAMP was emitting bare YYYY-MM-DD); OID_TEXT + bool now emits true/false (Postgres text shape) instead of t/f.
• ORDER BY / GROUP BY canonical-form registration so unaliased + aliased projections + qualified-ref forms all resolve via the lowercase canonical key.
• Flips the strict-xfail tests/integration/test_metabase_e2e.py::test_timestamp_round_trip_both_formats from PR DEV-1562: live-Metabase end-to-end pg-facade integration test suite #182's suite.

Base is egor/dev-1562-... (PR #182) because that branch carries test_metabase_e2e.py; will re-target main once #182 lands.

Two rounds of Codex review folded in pre-PR. Decisions documented inline in the commit message.

Test plan

• poetry run pytest -m \"not integration\" clean — verified locally: 4630 pass, 1 unrelated flake (test_save_memory_description_plumbing.py::test_cli_argparse_subprocess_accepts_description_flag, passes in isolation)
• poetry run ruff check slayer/ tests/ clean — verified
• poetry run pytest tests/integration/test_integration_pg_facade.py -m integration (new rejected-coercion case)
• Live-Metabase test_timestamp_round_trip_both_formats passes once DEV-1562: live-Metabase end-to-end pg-facade integration test suite #182 merges and this rebases onto main
• asyncpg repro from the Linear issue returns a datetime.datetime for SELECT CAST(ordered_at AS TIMESTAMP) FROM orders LIMIT 1

🤖 Generated with Claude Code

Summary by CodeRabbit

Release Notes

New Features

• Added CAST expression support in SQL projections enabling type coercions on column references
• Supports both CAST( AS type) and PostgreSQL column::type syntax
• Includes common type conversions such as date-to-timestamp and text coercions
• Provides clear error messages when cast operations are not supported

[linear]

DEV-1566

[coderabbitai]

📝 Walkthrough

Walkthrough

Implements CAST(<column> AS <type>) (and col::type) support in the Postgres facade translator. A strict coercion allowlist maps source/target type pairs; valid casts override the projected column's Postgres OID at the wire layer without changing engine execution. ORDER BY and GROUP BY validation is extended to canonicalize CAST expressions. Two value_to_text coercions handle DATE-to-TIMESTAMP widening and BOOL-to-TEXT encoding.

Changes

CAST Projection Support (DEV-1566)

Layer / File(s)	Summary
CAST type map, allowlist, and _ProjectionItem model slayer/facade/translator.py	Adds the sqlglot→SLayer DataType map, the per-source/target coercion allowlist (unknown source admits only TEXT), the canonical cast(<dotted> as <type>) key generator, and cast_target: Optional[DataType] on _ProjectionItem.
CAST detection, resolution, and projection wiring slayer/facade/translator.py	Adds _detect_column_cast and _resolve_column_cast_projection; wires them into _resolve_projection; overrides projection_types with cast_target for metric and dimension plans; registers canonical cast keys in item_by_projected_name for ORDER BY lookup.
ORDER BY and GROUP BY CAST canonicalization slayer/facade/translator.py	Extends _order_by_name to resolve CAST expressions by canonical key, and _validate_group_by to map CAST(col AS T) into the derived-dimension set.
Wire-layer OID value coercions slayer/pg_facade/types.py	Adds two OID-aware branches in value_to_text: widens date to datetime for OID_TIMESTAMP, and encodes bool as "true"/"false" for OID_TEXT.
Unit, wire-type, and integration tests tests/facade/test_translator.py, tests/pg_facade/test_types.py, tests/integration/test_integration_pg_facade.py, tests/integration/test_metabase_e2e.py	Adds DATE/BOOLEAN columns to the shared test catalog; adds a comprehensive CAST-projection test block covering allowlist, aliases, error messages, ORDER BY/GROUP BY, and metrics; adds OID override and value_to_text widening tests; adds an integration test for unsupported CAST error; removes xfail from the timestamp round-trip e2e test.
CAST projection documentation docs/interfaces/pg-facade.md	Documents CAST acceptance criteria, wire-layer OID-override mechanism, supported BI patterns, admitted coercions, unsupported forms, and error behavior.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Poem

🐇 A CAST is requested, the bunny checks twice,
The allowlist consulted — is this pair nice?
The OID is swapped at the wire's thin seam,
DATE widens to TIMESTAMP, a neat little dream.
TRY_CAST? Rejected! Expressions? No way!
The facade hops forward — DEV-1566 hooray! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title directly and accurately summarizes the main change: implementing CAST( AS ) support in the pg-facade projection system, which aligns with the primary objective and the DEV-1566 feature across all modified files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch egor/dev-1566-pg-facade-support-castcol-as-type-in-projection

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[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[coderabbitai]

🧹 Nitpick comments (1)

slayer/facade/translator.py (1)

1421-1423: ⚡ Quick win

Use keyword arguments for _alias_for_column_cast calls.

These new call sites use positional arguments on a 2-parameter function; switch to keyword arguments to match repo rules.

Proposed diff

-        return _alias_for_column_cast(
-            _column_to_dotted(inner_col, strip_prefix=strip_prefix), target,
-        )
+        return _alias_for_column_cast(
+            dotted=_column_to_dotted(inner_col, strip_prefix=strip_prefix),
+            target=target,
+        )
...
-                user_items.append(_alias_for_column_cast(
-                    _column_to_dotted(inner_col, strip_prefix=strip_prefix),
-                    target,
-                ))
+                user_items.append(_alias_for_column_cast(
+                    dotted=_column_to_dotted(inner_col, strip_prefix=strip_prefix),
+                    target=target,
+                ))
...
-        item_by_projected_name.setdefault(
-            _alias_for_column_cast(dotted, item.cast_target), item,
-        )
+        item_by_projected_name.setdefault(
+            _alias_for_column_cast(dotted=dotted, target=item.cast_target), item,
+        )

As per coding guidelines, **/*.py: “Use keyword arguments for functions with more than 1 parameter.”

Also applies to: 1454-1457, 1781-1783

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@slayer/facade/translator.py` around lines 1421 - 1423, The
_alias_for_column_cast function calls use positional arguments instead of
keyword arguments, which violates the repository's coding guidelines requiring
keyword arguments for functions with more than one parameter. In
slayer/facade/translator.py at lines 1421-1423 (the anchor location), convert
the positional arguments in the _alias_for_column_cast call to use explicit
keyword argument names. Apply the same conversion at the two sibling locations:
lines 1454-1457 and lines 1781-1783, ensuring all three call sites use keyword
arguments to match repository conventions.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@slayer/facade/translator.py`:
- Around line 1421-1423: The _alias_for_column_cast function calls use
positional arguments instead of keyword arguments, which violates the
repository's coding guidelines requiring keyword arguments for functions with
more than one parameter. In slayer/facade/translator.py at lines 1421-1423 (the
anchor location), convert the positional arguments in the _alias_for_column_cast
call to use explicit keyword argument names. Apply the same conversion at the
two sibling locations: lines 1454-1457 and lines 1781-1783, ensuring all three
call sites use keyword arguments to match repository conventions.

---

ℹ️ Review info

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Review profile: CHILL

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Run ID: 4dac113f-597d-4190-949f-68bf290a1e5d

📥 Commits

Reviewing files that changed from the base of the PR and between 3543b04 and 71bffe6.

📒 Files selected for processing (7)

• docs/interfaces/pg-facade.md
• slayer/facade/translator.py
• slayer/pg_facade/types.py
• tests/facade/test_translator.py
• tests/integration/test_integration_pg_facade.py
• tests/integration/test_metabase_e2e.py
• tests/pg_facade/test_types.py

💤 Files with no reviewable changes (1)

• tests/integration/test_metabase_e2e.py