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From "Santhosh Srinivasan (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-449) Schemas for bags should contain tuples all the time
Date Tue, 23 Sep 2008 02:46:44 GMT
Schemas for bags should contain tuples all the time
---------------------------------------------------

                 Key: PIG-449
                 URL: https://issues.apache.org/jira/browse/PIG-449
             Project: Pig
          Issue Type: Bug
    Affects Versions: types_branch
            Reporter: Santhosh Srinivasan
            Assignee: Santhosh Srinivasan
             Fix For: types_branch


The front end treats relations as operators that return bags.  When the schema of a load statement
is specified, the bag is associated with the schema specified by the user. Ideally, the schema
corresponds to the tuple contained in the bag. 

With PIG-380, the schema for bag constants are computed by the front end. The schema for the
bag contains the tuple which in turn contains the schema of the columns. This results in errors
when columns are accessed directly just like the load statements.

The front end should then treat access to the columns as a double dereference, i.e., access
the tuple inside the bag and then the column inside the tuple.

{code}
grunt> a = load '/user/sms/data/student.data' using PigStorage(' ') as (name, age, gpa);
grunt> b = foreach a generate {(16, 4.0e-2, 'hello')} as b:{t:(i: int, d: double, c: chararray)};

grunt> describe b;
b: {b: {t: (i: integer,d: double,c: chararray)}}

grunt> c = foreach b generate b.i;
111064 [main] ERROR org.apache.pig.tools.grunt.GruntParser  - java.io.IOException: Invalid
alias: i in {t: (i: integer,d: double,c: chararray)}
        at org.apache.pig.PigServer.parseQuery(PigServer.java:293)
        at org.apache.pig.PigServer.registerQuery(PigServer.java:258)
        at org.apache.pig.tools.grunt.GruntParser.processPig(GruntParser.java:432)
        at org.apache.pig.tools.pigscript.parser.PigScriptParser.parse(PigScriptParser.java:242)
        at org.apache.pig.tools.grunt.GruntParser.parseContOnError(GruntParser.java:93)
        at org.apache.pig.tools.grunt.Grunt.run(Grunt.java:58)
        at org.apache.pig.Main.main(Main.java:282)
Caused by: org.apache.pig.impl.logicalLayer.parser.ParseException: Invalid alias: i in {t:
(i: integer,d: double,c: chararray)}
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.AliasFieldOrSpec(QueryParser.java:5851)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.ColOrSpec(QueryParser.java:5709)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.BracketedSimpleProj(QueryParser.java:5242)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.BaseEvalSpec(QueryParser.java:4040)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.UnaryExpr(QueryParser.java:3909)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.CastExpr(QueryParser.java:3863)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.MultiplicativeExpr(QueryParser.java:3772)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.AdditiveExpr(QueryParser.java:3698)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.InfixExpr(QueryParser.java:3664)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.FlattenedGenerateItem(QueryParser.java:3590)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.FlattenedGenerateItemList(QueryParser.java:3500)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.GenerateStatement(QueryParser.java:3457)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.NestedBlock(QueryParser.java:2933)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.ForEachClause(QueryParser.java:2336)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.BaseExpr(QueryParser.java:973)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.Expr(QueryParser.java:748)
        at org.apache.pig.impl.logicalLayer.parser.QueryParser.Parse(QueryParser.java:549)
        at org.apache.pig.impl.logicalLayer.LogicalPlanBuilder.parse(LogicalPlanBuilder.java:60)
        at org.apache.pig.PigServer.parseQuery(PigServer.java:290)
        ... 6 more

111064 [main] ERROR org.apache.pig.tools.grunt.GruntParser  - Invalid alias: i in {t: (i:
integer,d: double,c: chararray)}
111064 [main] ERROR org.apache.pig.tools.grunt.GruntParser  - java.io.IOException: Invalid
alias: i in {t: (i: integer,d: double,c: chararray)}
grunt> c = foreach b generate b.t;
grunt> describe c;
c: {t: {i: integer,d: double,c: chararray}}

{code}

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