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author | Cheng Lian <lian@databricks.com> | 2016-02-21 22:53:15 +0800 |
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committer | Cheng Lian <lian@databricks.com> | 2016-02-21 22:53:15 +0800 |
commit | d9efe63ecdc60a9955f1924de0e8a00bcb6a559d (patch) | |
tree | 218879fda9e2285db67a72ed9fc42ec3ab61afa5 /streaming/src | |
parent | d806ed34365aa27895547297fff4cc48ecbeacdf (diff) | |
download | spark-d9efe63ecdc60a9955f1924de0e8a00bcb6a559d.tar.gz spark-d9efe63ecdc60a9955f1924de0e8a00bcb6a559d.tar.bz2 spark-d9efe63ecdc60a9955f1924de0e8a00bcb6a559d.zip |
[SPARK-12799] Simplify various string output for expressions
This PR introduces several major changes:
1. Replacing `Expression.prettyString` with `Expression.sql`
The `prettyString` method is mostly an internal, developer faced facility for debugging purposes, and shouldn't be exposed to users.
1. Using SQL-like representation as column names for selected fields that are not named expression (back-ticks and double quotes should be removed)
Before, we were using `prettyString` as column names when possible, and sometimes the result column names can be weird. Here are several examples:
Expression | `prettyString` | `sql` | Note
------------------ | -------------- | ---------- | ---------------
`a && b` | `a && b` | `a AND b` |
`a.getField("f")` | `a[f]` | `a.f` | `a` is a struct
1. Adding trait `NonSQLExpression` extending from `Expression` for expressions that don't have a SQL representation (e.g. Scala UDF/UDAF and Java/Scala object expressions used for encoders)
`NonSQLExpression.sql` may return an arbitrary user facing string representation of the expression.
Author: Cheng Lian <lian@databricks.com>
Closes #10757 from liancheng/spark-12799.simplify-expression-string-methods.
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