Adds the explicit decimal to integer downcasts (#1342)

partiql-planner/src/main/kotlin/org/partiql/planner/internal/typer/TypeLattice.kt

@@ -266,41 +266,57 @@ internal class TypeLattice private constructor(
                 SYMBOL to explicit(),
             )
             graph[DECIMAL] = relationships(
+                BOOL to explicit(),
                 INT8 to explicit(),
                 INT16 to explicit(),
                 INT32 to explicit(),
                 INT64 to explicit(),
-                BOOL to explicit(),
-                DECIMAL to explicit(),
-                DECIMAL_ARBITRARY to explicit(),
+                INT to explicit(),
+                DECIMAL to coercion(),
+                DECIMAL_ARBITRARY to coercion(),
                 FLOAT32 to explicit(),
                 FLOAT64 to explicit(),
                 STRING to explicit(),
                 SYMBOL to explicit(),
             )
-            graph[FLOAT32] = relationships(
+            graph[DECIMAL_ARBITRARY] = relationships(
                 BOOL to explicit(),
-                DECIMAL to explicit(),
+                INT8 to explicit(),
+                INT16 to explicit(),
+                INT32 to explicit(),
+                INT64 to explicit(),
+                INT to explicit(),
+                DECIMAL to coercion(),
                 DECIMAL_ARBITRARY to coercion(),
-                FLOAT32 to coercion(),
-                FLOAT64 to coercion(),
+                FLOAT32 to explicit(),
+                FLOAT64 to explicit(),
                 STRING to explicit(),
                 SYMBOL to explicit(),
             )
-            graph[FLOAT64] = relationships(
+            graph[FLOAT32] = relationships(
                 BOOL to explicit(),
-                DECIMAL to explicit(),
+                INT8 to unsafe(),
+                INT16 to unsafe(),
+                INT32 to unsafe(),
+                INT64 to unsafe(),
+                INT to unsafe(),
+                DECIMAL to unsafe(),
                 DECIMAL_ARBITRARY to coercion(),
+                FLOAT32 to coercion(),
                 FLOAT64 to coercion(),
                 STRING to explicit(),
                 SYMBOL to explicit(),
             )
-            graph[DECIMAL_ARBITRARY] = relationships(
+            graph[FLOAT64] = relationships(
                 BOOL to explicit(),
-                DECIMAL to explicit(),
+                INT8 to unsafe(),
+                INT16 to unsafe(),
+                INT32 to unsafe(),
+                INT64 to unsafe(),
+                INT to unsafe(),
+                DECIMAL to unsafe(),
                 DECIMAL_ARBITRARY to coercion(),
-                FLOAT32 to explicit(),
-                FLOAT64 to explicit(),
+                FLOAT64 to coercion(),
                 STRING to explicit(),
                 SYMBOL to explicit(),
             )

partiql-planner/src/test/kotlin/org/partiql/planner/internal/typer/PlanTyperTestsPorted.kt

@@ -33,6 +33,7 @@ import org.partiql.types.BagType
 import org.partiql.types.ListType
 import org.partiql.types.SexpType
 import org.partiql.types.StaticType
+import org.partiql.types.StaticType.Companion.unionOf
 import org.partiql.types.StructType
 import org.partiql.types.TupleConstraint
 import java.util.stream.Stream
@@ -448,6 +449,46 @@ class PlanTyperTestsPorted {
             ),
         )
 
+        @JvmStatic
+        fun castCases() = listOf(
+            SuccessTestCase(
+                name = "DECIMAL AS INT2",
+                key = key("cast-00"),
+                catalog = "pql",
+                expected = StaticType.INT2,
+            ),
+            SuccessTestCase(
+                name = "DECIMAL AS INT4",
+                key = key("cast-01"),
+                catalog = "pql",
+                expected = StaticType.INT4,
+            ),
+            SuccessTestCase(
+                name = "DECIMAL AS INT8",
+                key = key("cast-02"),
+                catalog = "pql",
+                expected = StaticType.INT8,
+            ),
+            SuccessTestCase(
+                name = "DECIMAL AS INT",
+                key = key("cast-03"),
+                catalog = "pql",
+                expected = StaticType.INT,
+            ),
+            SuccessTestCase(
+                name = "DECIMAL AS BIGINT",
+                key = key("cast-04"),
+                catalog = "pql",
+                expected = StaticType.INT8,
+            ),
+            SuccessTestCase(
+                name = "DECIMAL_ARBITRARY AS DECIMAL",
+                key = key("cast-05"),
+                catalog = "pql",
+                expected = StaticType.DECIMAL,
+            ),
+        )
+
         @JvmStatic
         fun sessionVariables() = listOf(
             SuccessTestCase(
@@ -3040,6 +3081,11 @@ class PlanTyperTestsPorted {
     @Execution(ExecutionMode.CONCURRENT)
     fun testIsType(tc: TestCase) = runTest(tc)
 
+    @ParameterizedTest
+    @MethodSource("castCases")
+    @Execution(ExecutionMode.CONCURRENT)
+    fun testCasts(tc: TestCase) = runTest(tc)
+
     // --------- Finish Parameterized Tests ------
 
     //

partiql-planner/src/testFixtures/resources/catalogs/default/pql/numbers.ion

@@ -1,5 +1,6 @@
 {
   type: "struct",
+  constraints: [closed],
   fields: [
     {
       name: "nullable_int16s",
@@ -69,6 +70,10 @@
         items: "int",
       },
     },
+    {
+      name: "d",
+      type: "decimal",
+    },
     {
       name: "decimals",
       type: {

partiql-planner/src/testFixtures/resources/inputs/schema_inferencer/casts.sql

@@ -0,0 +1,17 @@
+--#[cast-00]
+CAST(numbers.d AS INT2);
+
+--#[cast-01]
+CAST(numbers.d AS INT4);
+
+--#[cast-02]
+CAST(numbers.d AS INT8);
+
+--#[cast-03]
+CAST(numbers.d AS INT);
+
+--#[cast-04]
+CAST(numbers.d AS BIGINT);
+
+--#[cast-05]
+CAST(numbers.d AS DECIMAL);