[jira] [Updated] (ARROW-3458) [Gandiva] Add a string based expression parser

["Wes McKinney (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-3458?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wes McKinney updated ARROW-3458:
--------------------------------
    Component/s: C++

> [Gandiva] Add a string based expression parser
> ----------------------------------------------
>
>                 Key: ARROW-3458
>                 URL: https://issues.apache.org/jira/browse/ARROW-3458
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++, Gandiva
>            Reporter: Pindikura Ravindra
>            Priority: Major
>              Labels: gandiva
>
> Gandiva currently supports a tree-based expression builder. This requires writing a lot of code for even simple expressions.
> For eg. to build an expression for "a + b < 10", the code is :
> {code:java}
>    // schema for input fields
>   auto field0 = field("a", int32());
>   auto field1 = field("b", int32());
>   auto schema = arrow::schema({field0, field1});
>   // output fields
>   auto field_result = field("res", boolean());
>   // Build expression
>   auto node_f0 = TreeExprBuilder::MakeField(field0);
>   auto node_f1 = TreeExprBuilder::MakeField(field1);
>   auto literal_10 = TreeExprBuilder::MakeLiteral(10);
>   auto sum_expr =
>       TreeExprBuilder::MakeFunction("add", {node_f0, node_f1}, int32());
>   auto lt_expr =
>       TreeExprBuilder::MakeExpression("less_than", {sum_expr, literal_10}, field_result);
> {code}
> An alternate way to do this would be :
>  
> {code:java}
> // Build expression
> auto expr = StringExprBuilder::MakeExpression(schema, "a + b < 10", field_result);
> {code}
> The expression syntax should be close to that of SQL.
>  
> To begin with, this'll simplify writing tests. And, it will provide an easier api to work with gandiva.



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