[PIG-449] Schemas for bags should contain tuples all the time

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.2.0
• Fix Version/s: 0.2.0
• Assignee: Pradeep Kamath
• Reporter: Santhosh Muthur Srinivasan
• Created: 23/Sep/08 02:46
• Updated: 24/Mar/10 22:04
• Resolved: 09/Dec/08 02:02

Description

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.

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}}