Dhiraj Kumar created HIVE-15291:
-----------------------------------

             Summary: Comparison of timestamp fails if only date part is 
provided. 
                 Key: HIVE-15291
                 URL: https://issues.apache.org/jira/browse/HIVE-15291
             Project: Hive
          Issue Type: Bug
          Components: Hive, UDF
    Affects Versions: 2.1.0
            Reporter: Dhiraj Kumar


Summary : If a query needs to compare two timestamp with one timestamp provided 
in "YYYY-MM-DD" format and skipping the time part, it returns incorrect result. 

Steps to reproduce : 

1. Start a hive-cli. 
2. Fire up the query -> select cast("2016-12-31 12:00:00" as timestamp) > 
"2016-12-30";
3. Expected result : true
4. Actual result : NULL

Detailed description : 
If two primitives of different type needs to compared, a common comparator type 
is chosen. Prior to 2.1, Common type Text was chosen to compare Timestamp type 
and Text type. 

In version 2.1, Common type Timestamp is chosen to compare Timestamp type and 
Text type. This leads to converting Text type (YYYY-MM-DD) to be converted into 
java.sql.Timestamp which throws Exception saying the input is not in proper 
format. The exception is suppressed and a null is returned. 

Code below from org.apache.hadoop.hive.ql.exec.FunctionRegistry
{code:java}
if (pgA == PrimitiveGrouping.STRING_GROUP && pgB == 
PrimitiveGrouping.DATE_GROUP) {
      return b;
    }
    // date/timestamp is higher precedence than String_GROUP
    if (pgB == PrimitiveGrouping.STRING_GROUP && pgA == 
PrimitiveGrouping.DATE_GROUP) {
      return a;
    }
{code}


The bug was introduced in  
[HIVE-13381|https://issues.apache.org/jira/browse/HIVE-13381]



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