gustavodemorais commented on code in PR #27603:
URL: https://github.com/apache/flink/pull/27603#discussion_r2816073876
##########
flink-table/flink-table-common/src/test/java/org/apache/flink/table/types/LogicalTypeCastsTest.java:
##########
@@ -273,4 +279,140 @@ void test(
.as("Supports explicit casting")
.isEqualTo(supportsExplicit);
}
+
+ /**
+ * Test data for injective cast tests. Each argument contains:
(sourceType, targetType,
+ * expectedInjective).
+ */
+ private static Stream<Arguments> injectiveCastTestData() {
+ return Stream.of(
+ // Integer widenings are injective
+ Arguments.of(new SmallIntType(), new BigIntType(), true),
+ Arguments.of(new IntType(), new BigIntType(), true),
+ Arguments.of(new TinyIntType(), new IntType(), true),
+ Arguments.of(new TinyIntType(), new SmallIntType(), true),
+
+ // Explicit casts to STRING from integer types are injective
+ Arguments.of(new TinyIntType(), VarCharType.STRING_TYPE, true),
+ Arguments.of(new SmallIntType(), VarCharType.STRING_TYPE,
true),
+ Arguments.of(new IntType(), VarCharType.STRING_TYPE, true),
+ Arguments.of(new BigIntType(), VarCharType.STRING_TYPE, true),
+
+ // FLOAT/DOUBLE to STRING are injective
+ Arguments.of(new FloatType(), VarCharType.STRING_TYPE, true),
+ Arguments.of(new DoubleType(), VarCharType.STRING_TYPE, true),
+
+ // Explicit casts to STRING from boolean are injective
+ Arguments.of(new BooleanType(), VarCharType.STRING_TYPE, true),
+
+ // Explicit casts to STRING from date/time types are injective
+ Arguments.of(new DateType(), VarCharType.STRING_TYPE, true),
+ Arguments.of(new TimestampType(3), VarCharType.STRING_TYPE,
true),
+ Arguments.of(new TimestampType(9), VarCharType.STRING_TYPE,
true),
+ Arguments.of(new LocalZonedTimestampType(3),
VarCharType.STRING_TYPE, true),
+ Arguments.of(new ZonedTimestampType(3),
VarCharType.STRING_TYPE, true),
+
+ // Explicit casts to CHAR are also injective for the same
source types
+ Arguments.of(new IntType(), new CharType(100), true),
+ Arguments.of(new BigIntType(), new CharType(100), true),
+
+ // CHAR → VARCHAR widening is injective
+ Arguments.of(new CharType(10), VarCharType.STRING_TYPE, true),
+
+ // BINARY → VARBINARY widening is injective
+ Arguments.of(new BinaryType(10), new VarBinaryType(100), true),
+
+ // Integer → DECIMAL is injective (exact representation)
+ Arguments.of(new TinyIntType(), new DecimalType(10, 0), true),
+ Arguments.of(new SmallIntType(), new DecimalType(10, 0), true),
+ Arguments.of(new IntType(), new DecimalType(10, 0), true),
+ Arguments.of(new BigIntType(), new DecimalType(20, 0), true),
+
+ // DECIMAL → DECIMAL identity is injective
+ Arguments.of(new DecimalType(10, 2), new DecimalType(10, 2),
true),
+
+ // FLOAT → DOUBLE widening is injective
+ Arguments.of(new FloatType(), new DoubleType(), true),
+
+ // Narrowing casts are NOT injective (lossy)
+ Arguments.of(VarCharType.STRING_TYPE, new IntType(), false),
+ Arguments.of(new BigIntType(), new IntType(), false),
+ Arguments.of(new DoubleType(), new FloatType(), false),
+
+ // TIMESTAMP → DATE is NOT injective (loses time-of-day
information)
+ // even though it is an implicit cast
+ Arguments.of(new TimestampType(3), new DateType(), false),
+
+ // DECIMAL to STRING is NOT considered injective
+ Arguments.of(new DecimalType(10, 2), VarCharType.STRING_TYPE,
false),
+
+ // BYTES to STRING is NOT injective (invalid UTF-8 sequences
collapse)
+ Arguments.of(new VarBinaryType(100), VarCharType.STRING_TYPE,
false),
+ Arguments.of(new BinaryType(100), VarCharType.STRING_TYPE,
false),
+
+ // TIME to STRING is NOT injective (not in the whitelist)
+ Arguments.of(new TimeType(3), VarCharType.STRING_TYPE, false),
+
+ // INT → FLOAT/DOUBLE are NOT injective (even though implicit)
+ // because floating point is not in the injective rules
+ Arguments.of(new IntType(), new FloatType(), false),
+ Arguments.of(new IntType(), new DoubleType(), false),
Review Comment:
But I'll update the comment to communicate that
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