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 "]" | ... | 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:
delimiters : "." | "," | ";" | "(" | ")" | "[" | "]" | ...
identChar : letter | "_"
baseExpression : expression "[" expression "]" | expression "." ident | ... | 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 "]" | expression "." ident | ... | dotExpressionHeader | ident | ...
I passed all test cases under sql locally and add a more complex case.
"arrayOfStruct.field1 to access all values of field1" is not supported yet. Since this PR has changed a lot of code, I will open another PR for it.
I'm not familiar with the latter optimize phase, please correct me if I missed something.
Author: Wenchen Fan <cloud0fan@163.com>
Author: Michael Armbrust <michael@databricks.com>
Closes#2230 from cloud-fan/dot and squashes the following commits:
e1a8898 [Wenchen Fan] remove support for arbitrary nested arrays
ee8a724 [Wenchen Fan] rollback LogicalPlan, support dot operation on nested array type
a58df40 [Michael Armbrust] add regression test for doubly nested data
16bc4c6 [Wenchen Fan] some enhance
95d733f [Wenchen Fan] split long line
dc31698 [Wenchen Fan] SPARK-2096 Correctly parse dot notations
e4f4886d71
