[PIG-1788] relation-as-scalar error messages should indicate the field being used as scalar

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.9.0
• Assignee: Laukik Chitnis
• Reporter: Thejas Nair
• Created: 05/Jan/11 20:51
• Updated: 04/Aug/11 00:35
• Resolved: 15/Apr/11 23:55

Description

Issue 1

grunt> l = load 'x' as (a,b,c);        
grunt> g = group l by a;
grunt> f = foreach g generate COUNT(g);       -- g is unintentionally being used as scalar , the user intends it to be COUNT(l) . 
2011-01-05 12:44:53,098 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1000: Error during parsing. Scalars can be only used with projections

Since the user did not intend to use a scalar, the scalar error messages are hard to understand.
It will be useful to have the relation being used in scalar context in the error message. Something like - "ERROR 1000: Error during parsing. Relation g being used in scalar context at ... .Scalars can be only used with projections"

Issue 2
The error message "Scalars can be only used with projections" is not easy to understand. A better error message is needed, something like "A column needs to be projected from relation used in scalar context."