From 3a5db14bbdd5d22d06b011dcdef64df512c63de0 Mon Sep 17 00:00:00 2001
From: Kevin Longe <273747162+kvlonge@users.noreply.github.com>
Date: Fri, 18 Sep 2026 01:24:46 +0100
Subject: [PATCH] fix: infer SQL predicate output types

---
 .../compiler/compile/_helpers/analysis/columns.py    | 12 ++++++++++++
 src/sqlbuild/compiler/sql_analysis/constants.py      |  1 +
 .../compile/_helpers/test_sql_analysis_columns.py    | 12 ++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/src/sqlbuild/compiler/compile/_helpers/analysis/columns.py b/src/sqlbuild/compiler/compile/_helpers/analysis/columns.py
index 0f79b0fa5b..ebb8c1c4b9 100644
--- a/src/sqlbuild/compiler/compile/_helpers/analysis/columns.py
+++ b/src/sqlbuild/compiler/compile/_helpers/analysis/columns.py
@@ -135,6 +135,9 @@
 from sqlbuild.compiler.sql_analysis.constants import (
     POLYGLOT_ANALYSIS_UPSTREAM as _POLYGLOT_ANALYSIS_UPSTREAM,
 )
+from sqlbuild.compiler.sql_analysis.constants import (
+    POLYGLOT_BOOLEAN_RESULT_KINDS as _POLYGLOT_BOOLEAN_RESULT_KINDS,
+)
 from sqlbuild.compiler.sql_analysis.constants import (
     POLYGLOT_CAST_KINDS as _POLYGLOT_CAST_KINDS,
 )
@@ -165,6 +168,9 @@
 from sqlbuild.compiler.sql_analysis.constants import (
     POLYGLOT_KIND_COUNT as _POLYGLOT_KIND_COUNT,
 )
+from sqlbuild.compiler.sql_analysis.constants import (
+    POLYGLOT_KIND_IS_NULL as _POLYGLOT_KIND_IS_NULL,
+)
 from sqlbuild.compiler.sql_analysis.constants import (
     POLYGLOT_KIND_LITERAL as _POLYGLOT_KIND_LITERAL,
 )
@@ -1280,6 +1286,8 @@ def _polyglot_expression_type(
     )
     if function_type is not None:
         return function_type
+    if kind in _POLYGLOT_BOOLEAN_RESULT_KINDS:
+        return "BOOLEAN"
     if kind not in _POLYGLOT_CAST_KINDS:
         return None
     payload: object = expression.to_dict().get(kind, {})
@@ -1364,6 +1372,8 @@ def _infer_polyglot_nullability(
         return InferredNullability.UNKNOWN
     if kind == _POLYGLOT_KIND_COUNT:
         return InferredNullability.NON_NULL
+    if kind == _POLYGLOT_KIND_IS_NULL:
+        return InferredNullability.NON_NULL
     if kind == _POLYGLOT_KIND_COALESCE:
         child_nullabilities: list[InferredNullability] = [
             _infer_polyglot_nullability(
@@ -1408,6 +1418,8 @@ def _infer_polyglot_shallow_nullability(
         return InferredNullability.NON_NULL
     if kind == _POLYGLOT_KIND_COUNT:
         return InferredNullability.NON_NULL
+    if kind == _POLYGLOT_KIND_IS_NULL:
+        return InferredNullability.NON_NULL
     if kind == _POLYGLOT_KIND_COLUMN:
         return InferredNullability.UNKNOWN
     if kind == _POLYGLOT_KIND_CAST:
diff --git a/src/sqlbuild/compiler/sql_analysis/constants.py b/src/sqlbuild/compiler/sql_analysis/constants.py
index 8dbe2e8bd3..8de11714a0 100644
--- a/src/sqlbuild/compiler/sql_analysis/constants.py
+++ b/src/sqlbuild/compiler/sql_analysis/constants.py
@@ -60,6 +60,7 @@
         "ilike",
         "in",
         "is",
+        POLYGLOT_KIND_IS_NULL,
         "like",
         "lt",
         "lte",
diff --git a/tests/unit/src/sqlbuild/compiler/compile/_helpers/test_sql_analysis_columns.py b/tests/unit/src/sqlbuild/compiler/compile/_helpers/test_sql_analysis_columns.py
index 2ef2ffbda6..2ff2d134bd 100644
--- a/tests/unit/src/sqlbuild/compiler/compile/_helpers/test_sql_analysis_columns.py
+++ b/tests/unit/src/sqlbuild/compiler/compile/_helpers/test_sql_analysis_columns.py
@@ -433,6 +433,18 @@
                 ),
             ),
         ),
+        InferColumnsTestCase(
+            description="infers null predicates as non-null booleans",
+            query_sql=('SELECT status IS NOT NULL AS has_status FROM __ref("orders")'),
+            column_nullability_by_table={"orders": {"status": InferredNullability.NULLABLE}},
+            expected_columns=(
+                InferredColumn(
+                    name="has_status",
+                    type="BOOLEAN",
+                    nullability=InferredNullability.NON_NULL,
+                ),
+            ),
+        ),
         InferColumnsTestCase(
             description="refines filtered CTE output nullability",
             query_sql=(