[GitHub] spark pull request: SPARK-2096 Correctly parse dot notations

[cloud-fan]

GitHub user cloud-fan opened a pull request:

    https://github.com/apache/spark/pull/2230

    SPARK-2096 Correctly parse dot notations

    First let me write down the current `projections` grammar of spark sql:
    
        expression                : orExpression
        orExpression              : andExpression {"or" andExpression}
        andExpression             : comparisonExpression {"and" 
comparisonExpression}
        comparisonExpression      : termExpression | termExpression "=" 
termExpression | termExpression ">" termExpression | ...
        termExpression            : productExpression {"+"|"-" 
productExpression}
        productExpression         : baseExpression {"*"|"/"|"%" baseExpression}
        baseExpression            : expression "[" expression "]" | "(" 
expression ")" | ident | ...
        ident                     : identChar {identChar | digit} | delimiters 
| ...
        identChar                 : letter | "_" | "."
        delimiters                : "," | ";" | "(" | ")" | "[" | "]" | ...
        projection                : expression [["AS"] ident]
        projections               : projection { "," projection}
    
    For something like `a.b.c[1]`, it will be parsed as:
    <img src="http://img51.imgspice.com/i/03008/4iltjsnqgmtt_t.jpg"; border=0>
    But for something like `a[1].b`, the current grammar can't parse it 
correctly.
    A simple solution is written in `ParquetQuerySuite#NestedSqlParser`, 
changed grammars are:
    
        identChar                 : letter | "_"
        baseExpression            : expression "[" expression "]" | expression 
"." ident | "(" expression ")" | ident | ...
    This works well, but can't cover some corner case like `select t.a.b from 
table as t`:
    <img src="http://img51.imgspice.com/i/03008/v2iau3hoxoxg_t.jpg"; border=0>
    `t.a.b` parsed as `GetField(GetField(UnResolved("t"), "a"), "b")` instead 
of `GetField(UnResolved("t.a"), "b")` using this new grammar.
    However, we can't resolve `t` as it's not a filed, but the whole table.(if 
we could do this, then `select t from table as t` is legal, which is unexpected)
    My solution is:
    
        dotExpressionHeader       : ident "." ident
        baseExpression            : expression "[" expression "]" | 
dotExpressionHeader | expression "." ident | "(" expression ")" | ident | ...
    I passed all test cases under sql locally and add a more complex case.
    I'm not familiar with the latter optimize phase, please correct me if I 
missed something.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/cloud-fan/spark dot

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/spark/pull/2230.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #2230
    
----
commit de630829028d9d4a7ef55b8a0ff31e09f0b549d9
Author: Wenchen Fan <cloud0...@163.com>
Date:   2014-09-01T11:10:02Z

    SPARK-2096 Correctly parse dot notations

----


---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---

---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org