[GitHub] [flink] dawidwys commented on a change in pull request #12593: [FLINK-13783][table] Implement type inference for string functions

[GitBox <gi...@apache.org>]

dawidwys commented on a change in pull request #12593:
URL: https://github.com/apache/flink/pull/12593#discussion_r439362209



##########
File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/inference/TypeStrategies.java
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@@ -315,6 +330,32 @@ public static TypeStrategy nullable(TypeStrategy initialStrategy) {
 		return Optional.of(fromLogicalToDataType(inferredType));
 	};
 
+	/**
+	 * Type strategy that returns the type of a string concatenation. It assumes that the first two
+	 * arguments are of the same family of either {@link LogicalTypeFamily#BINARY_STRING} or
+	 * {@link LogicalTypeFamily#CHARACTER_STRING}.
+	 */
+	public static final TypeStrategy STRING_CONCAT = callContext -> {
+		final List<DataType> argumentDataTypes = callContext.getArgumentDataTypes();
+		final LogicalType type1 = argumentDataTypes.get(0).getLogicalType();
+		final LogicalType type2 = argumentDataTypes.get(1).getLogicalType();
+		int length = getLength(type1) + getLength(type2);
+		if (length < 0) {

Review comment:
       nit: add a comment //overflow




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