mihaibudiu commented on code in PR #3779:
URL: https://github.com/apache/calcite/pull/3779#discussion_r1596000032
##########
core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java:
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@@ -1822,6 +1823,35 @@ public static RelDataType
extractLastNFields(RelDataTypeFactory typeFactory,
type.getFieldList().subList(fieldsCnt - numToKeep, fieldsCnt));
}
+ /**
+ * Returns whether the decimal value can be represented without information
loss
+ * using the specified type.
+ * For example, 1111.11
+ * - cannot be represented exactly using DECIMAL(3, 1) since it overflows.
+ * - cannot be represented exactly using DECIMAL(6, 3) since it overflows.
+ * - cannot be represented exactly using DECIMAL(6, 1) since it requires
rounding.
+ * - can be represented exactly using DECIMAL(6, 2)
+ *
+ * @param value A decimal value
+ * @param toType A DECIMAL type.
+ * @return whether the value is valid for the type
+ */
+ public static boolean canBeRepresentedExactly(@Nullable BigDecimal value,
RelDataType toType) {
+ assert toType.getSqlTypeName() == SqlTypeName.DECIMAL;
+ if (value == null) {
+ return true;
+ }
+ value = value.stripTrailingZeros();
+ if (value.scale() < 0) {
Review Comment:
Frankly negative scales are something I don't understand well.
Many SQL dialects do not accept negative scales, but Calcite allegedly does,
although there aren't many tests about that.
Maybe we can file a separate issue about testing negative scales in Calcite,
I expect it may uncover quite a few bugs.
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