Treating integers and strings in PigStorage

                 Key: PIG-724
             Project: Pig
          Issue Type: Bug
          Components: impl
    Affects Versions: 1.0.1
            Reporter: Santhosh Srinivasan
             Fix For: 1.0.1

Currently, PigStorage cannot treats the materialized string 123 as an integer 
with the value 123. If the user intended this to be the string 123, PigStorage 
cannot deal with it. This reasoning also applies to doubles. Due to this issue, 
maps that contain values which are of the same type but manifest the issue 
discussed at beginning of the paragraph, Pig throws its hands up at runtime.  
An example to illustrate the problem will help.

In the example below a sample row in the data (map.txt) contains the following:


When Pig tries to convert the stream to a map, it creates a Map<Object, Object> 
where the key is a string and the value is an integer. Running the script shown 
below, results in a run-time error.

grunt> a = load 'map.txt' as (themap: map[]);                    
grunt> b = filter a by (chararray)(themap#'key01') == 'hello';                  
grunt> dump b;

2009-03-18 15:19:03,773 [main] INFO  
- 0% complete
2009-03-18 15:19:28,797 [main] ERROR 
- Map reduce job failed
2009-03-18 15:19:28,817 [main] ERROR - ERROR 
1081: Cannot cast to chararray. Expected bytearray but received: int

There are two ways to resolve this issue:

1. Change the conversion routine for bytesToMap to return a map where the value 
is a bytearray and not the actual type. This change breaks backward 
2. Introduce checks in POCast where conversions that are legal in the type 
checking world are allowed, i.e., run time checks will be made to check for 
compatible casts. In the above example, an int can be converted to a chararray 
and the cast will be made. If on the other hand, it was a chararray to int 
conversion then an exception will be thrown.

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