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https://issues.apache.org/jira/browse/DRILL-6768?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16645090#comment-16645090
 ] 

ASF GitHub Bot commented on DRILL-6768:
---------------------------------------

KazydubB commented on a change in pull request #1494: DRILL-6768: Improve 
to_date, to_time and to_timestamp and correspondi…
URL: https://github.com/apache/drill/pull/1494#discussion_r224049673
 
 

 ##########
 File path: 
logical/src/main/java/org/apache/drill/common/expression/fn/ToFunctions.java
 ##########
 @@ -0,0 +1,130 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.common.expression.fn;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.drill.common.types.TypeProtos.DataMode;
+import org.apache.drill.common.types.TypeProtos.MinorType;
+
+public class ToFunctions {
+
+  private static Map<MinorType, String> TO_FUNC = new HashMap<>();
+  /** The to functions that need to be replaced (if
+   * "drill.exec.functions.cast_empty_string_to_null" is set to true). */
+  private static Set<String> TO_FUNC_REPLACEMENT_NEEDED = new HashSet<>();
+  /** Map from the replaced functions to the new ones (for non-nullable 
VARCHAR). */
+  private static Map<String, String> FUNC_REPLACEMENT_FROM_NONNULLABLE_VARCHAR 
= new HashMap<>();
+  /** Map from the replaced functions to the new ones (for non-nullable 
VAR16CHAR). */
+  private static Map<String, String> 
FUNC_REPLACEMENT_FROM_NONNULLABLE_VAR16CHAR = new HashMap<>();
+  /** Map from the replaced functions to the new ones (for non-nullable 
VARBINARY). */
+  private static Map<String, String> 
FUNC_REPLACEMENT_FROM_NONNULLABLE_VARBINARY = new HashMap<>();
+  /** Map from the replaced functions to the new ones (for nullable VARCHAR). 
*/
+  private static Map<String, String> FUNC_REPLACEMENT_FROM_NULLABLE_VARCHAR = 
new HashMap<>();
+  /** Map from the replaced functions to the new ones (for nullable 
VAR16CHAR). */
+  private static Map<String, String> FUNC_REPLACEMENT_FROM_NULLABLE_VAR16CHAR 
= new HashMap<>();
+  /** Map from the replaced functions to the new ones (for nullable 
VARBINARY). */
+  private static Map<String, String> FUNC_REPLACEMENT_FROM_NULLABLE_VARBINARY 
= new HashMap<>();
+
+  static {
+    TO_FUNC.put(MinorType.DATE, "to_date");
+    TO_FUNC.put(MinorType.TIME, "to_time");
+    TO_FUNC.put(MinorType.TIMESTAMP, "to_timestamp");
+
+    setupReplacementFunctions(MinorType.DATE, "NullableDate");
+    setupReplacementFunctions(MinorType.TIME, "NullableTime");
+    setupReplacementFunctions(MinorType.TIMESTAMP, "NullableTimeStamp");
+  }
+
+  private static void setupReplacementFunctions(MinorType type, String toType) 
{
 
 Review comment:
   Merged these two classes to a single FunctionsUtil.

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> Improve to_date, to_time and to_timestamp and corresponding cast functions to 
> handle empty string when `drill.exec.functions.cast_empty_string_to_null` 
> option is enabled
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DRILL-6768
>                 URL: https://issues.apache.org/jira/browse/DRILL-6768
>             Project: Apache Drill
>          Issue Type: Improvement
>    Affects Versions: 1.14.0
>            Reporter: Bohdan Kazydub
>            Assignee: Bohdan Kazydub
>            Priority: Major
>              Labels: doc-impacting
>             Fix For: 1.15.0
>
>
> When `drill.exec.functions.cast_empty_string_to_null` option is enabled
> `to_date`, `to_time` and `to_timestamp` functions while converting string to 
> according type in case if null or empty string values are passed will return 
> NULL (to avoid CASE clauses which are littering a query and will work in 
> accordance with their respective CAST counterparts) for both cases.
>  
>   
>   
> CASTs will  be handled in a similar way (uniformly with numeric types):
>  
> ||Value to cast||Now||Will be||
> |NULL|NULL|NULL|
> |'' (empty string)|Error in many cases (except numerical types)|NULL|
>  CAST empty string to null (in case of enabled option) will be supported by 
> DATE, TIME, TIMESTAMP, INTERVAL YEAR, INTERVAL MONTH and INTERVAL DAY 
> functions in addition to numeric types.
>  
> *For documentation*
> TBA



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