Treating integers and strings in PigStorage
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Key: PIG-724
URL: https://issues.apache.org/jira/browse/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:
[key01#35,key02#value01]
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.
{code}
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
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher
- 0% complete
2009-03-18 15:19:28,797 [main] ERROR
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher
- Map reduce job failed
2009-03-18 15:19:28,817 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR
1081: Cannot cast to chararray. Expected bytearray but received: int
{code}
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
compatibility
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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