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From "Santhosh Srinivasan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-159) Make changes to the parser to support new types functionality
Date Wed, 14 May 2008 17:40:57 GMT

    [ https://issues.apache.org/jira/browse/PIG-159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12596844#action_12596844
] 

Santhosh Srinivasan commented on PIG-159:
-----------------------------------------

With my last patch, I added getFieldSchema for expression operators. Expressions will generate
field schemas and not schemas. Schemas are associated only with the relational operators.
The top level operators will generate schemas based on the field schemas returned by the constituent
expressions. 

ExpressionOperator extends LogicalOperator which has the abstract method getSchem, and the
method getType. As a result, these methods are present in ExpressionOperator. The getSchema
method for expressions will return null. The getType method will be used for type checking
(e.g.: the arithmetic operators LOAdd, LOSubtract, etc.)

I will remove the getSchema methods in the expression operators and move them up to the parent
EpxressionOperator class.

> Make changes to the parser to support new types functionality
> -------------------------------------------------------------
>
>                 Key: PIG-159
>                 URL: https://issues.apache.org/jira/browse/PIG-159
>             Project: Pig
>          Issue Type: Sub-task
>          Components: impl
>            Reporter: Alan Gates
>            Assignee: Alan Gates
>         Attachments: parser_chages_v5.patch
>
>
> In order to support the new types functionality described in http://wiki.apache.org/pig/PigTypesFunctionalSpec,
the parse needs to change in the following ways:
> 1) AS needs to support types in addition to aliases.  So where previously it was legal
to say:
> a = load 'myfile' as a, b, c;
> it will now also be legal to say
> a = load 'myfile' as a integer, b float, c chararray;
> 2) Non string constants need to be supported.  This includes non-string atomic types
(integer, long, float, double) and the non-atomic types bags, tuples, and maps.
> 3) A cast operator needs to be added so that fields can be explicitly casted.
> 4) Changes to DEFINE, to allow users to declare arguments and return types for UDFs

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