danny0405 commented on a change in pull request #1862: [CALCITE-3864] Implement
Concat function
URL: https://github.com/apache/calcite/pull/1862#discussion_r398602055
##
File path: core/src/main/java/org/apache/calcite/sql/type/ReturnTypes.java
##
@@ -655,6 +655,59 @@ public int size() {
return ret;
};
+
+ /**
+ * Type-inference strategy for String concatenation.
+ * Result is varying if either input is; otherwise fixed.
+ * For example,
+ *
+ * concat(cast('a' as varchar(2)), cast('b' as varchar(3)),cast('c' as
varchar(2)))
+ * returns varchar(7),
+ *
+ * concat(cast('a' as varchar), cast('b' as varchar(2), cast('c' as
varchar(2
+ * returns varchar,
+ *
+ * concat(cast('a' as varchar(65535)), cast('b' as varchar(2)), cast('c' as
varchar(2)))
+ * returns varchar
+ */
+ public static final SqlReturnTypeInference MULTIVALENT_STRING_SUM_PRECISION =
+ opBinding -> {
+boolean hasPrecisionNotSpecifiedOperand = false;
+boolean precisionOverflow = false;
+int typePrecision;
+long amount = 0;
+List operandTypes = opBinding.collectOperandTypes();
+final RelDataTypeFactory typeFactory = opBinding.getTypeFactory();
+final RelDataTypeSystem typeSystem = typeFactory.getTypeSystem();
+for (RelDataType operandType: operandTypes) {
+ int operandPrecision = operandType.getPrecision();
+ amount = (long) operandPrecision + amount;
+ if (operandPrecision == RelDataType.PRECISION_NOT_SPECIFIED) {
+hasPrecisionNotSpecifiedOperand = true;
+break;
+ }
+ if (amount > typeSystem.getMaxPrecision(SqlTypeName.VARCHAR)) {
+precisionOverflow = true;
+break;
+ }
+}
+if (hasPrecisionNotSpecifiedOperand || precisionOverflow) {
+ typePrecision = RelDataType.PRECISION_NOT_SPECIFIED;
+} else {
+ typePrecision = (int) amount;
+}
+
+return opBinding.getTypeFactory()
+.createSqlType(SqlTypeName.VARCHAR, typePrecision);
+ };
+
+ /**
+ * Same as {@link #MULTIVALENT_STRING_SUM_PRECISION} and using
+ * {@link org.apache.calcite.sql.type.SqlTypeTransforms#TO_NULLABLE}
+ */
Review comment:
End up the comment with dot.
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