DonnyZone commented on a change in pull request #1563: [CALCITE-3435] Enable
decimal modulus operation to allow numeric with non-zero scale
URL: https://github.com/apache/calcite/pull/1563#discussion_r343632705
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File path:
core/src/main/java/org/apache/calcite/rel/type/RelDataTypeSystemImpl.java
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@@ -252,6 +253,74 @@ public boolean allowExtendedTrim() {
return false;
}
+ /**
+ * Infers the return type of a decimal modulus operation. Decimal modulus
+ * involves at least one decimal operand.
+ *
+ * <p>Rules:
+ *
+ * <ul>
+ * <li>Let p1, s1 be the precision and scale of the first operand</li>
+ * <li>Let p2, s2 be the precision and scale of the second operand</li>
+ * <li>Let p, s be the precision and scale of the result</li>
+ * <li>Let d be the number of whole digits in the result</li>
+ * <li>Then the result type is a decimal with:
+ * <ul>
+ * <li>s = max(s1, s2)</li>
+ * <li>p = min(p1 - s1, p2 - s2) + max(s1, s2)</li>
+ * </ul>
+ * </li>
+ * <li>p and s are capped at their maximum values</li>
+ * </ul>
+ *
+ * @param typeFactory typeFactory used to create output type
+ * @param type1 type of the first operand
+ * @param type2 type of the second operand
+ * @return the result type for a decimal modulus, or null if decimal
+ * modulus should not be applied to the operands.
+ */
+ @Override public RelDataType deriveDecimalModType(RelDataTypeFactory
typeFactory,
+ RelDataType type1, RelDataType type2) {
+ if (SqlTypeUtil.isExactNumeric(type1)
+ && SqlTypeUtil.isExactNumeric(type2)) {
+ if (SqlTypeUtil.isDecimal(type1)
+ || SqlTypeUtil.isDecimal(type2)) {
+ // Java numeric will always have invalid precision/scale,
+ // use its default decimal precision/scale instead.
+ type1 = RelDataTypeFactoryImpl.isJavaType(type1)
+ ? typeFactory.decimalOf(type1)
+ : type1;
+ type2 = RelDataTypeFactoryImpl.isJavaType(type2)
+ ? typeFactory.decimalOf(type2)
+ : type2;
+ int p1 = type1.getPrecision();
+ int p2 = type2.getPrecision();
+ int s1 = type1.getScale();
+ int s2 = type2.getScale();
+ // keep consistency with SQL standard
+ if (s1 == 0 && s2 == 0) {
+ return type2;
+ }
+
+ int scale = Math.max(s1, s2);
+ assert scale <= getMaxNumericScale();
+
+ int precision = Math.min(p1 - s1, p2 - s2) + Math.max(s1, s2);
+ precision = Math.min(precision, getMaxNumericPrecision());
+ assert precision > 0;
+
+ RelDataType ret;
+ ret = typeFactory.createSqlType(
+ SqlTypeName.DECIMAL,
+ precision,
+ scale);
Review comment:
Ok
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