[pick](Variant) truncate key when column is variant type when crea… (#40238)

#39988

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/info/CreateMTMVInfo.java

@@ -265,7 +265,7 @@ public class CreateMTMVInfo {
                 if (type.isFloatLikeType() || type.isStringType() || type.isJsonType()
                         || catalogType.isComplexType() || type.isBitmapType() || type.isHllType()
                         || type.isQuantileStateType() || type.isJsonType() || type.isStructType()
-                        || column.getAggType() != null) {
+                        || column.getAggType() != null || type.isVariantType()) {
                     break;
                 }
                 keys.add(column.getName());