[spark] branch branch-3.1 updated: [SPARK-33818][SQL][DOC] Add descriptions about `spark.sql.parser.quotedRegexColumnNames` in the SQL documents

[do...@apache.org]

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dongjoon pushed a commit to branch branch-3.1
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The following commit(s) were added to refs/heads/branch-3.1 by this push:
     new 78d29fe  [SPARK-33818][SQL][DOC] Add descriptions about `spark.sql.parser.quotedRegexColumnNames` in the SQL documents
78d29fe is described below

commit 78d29feca632d000783d7a1293bf164e19277fb9
Author: angerszhu <an...@gmail.com>
AuthorDate: Thu Jan 7 18:55:27 2021 -0800

    [SPARK-33818][SQL][DOC] Add descriptions about `spark.sql.parser.quotedRegexColumnNames` in the SQL documents
    
    ### What changes were proposed in this pull request?
    According to https://github.com/apache/spark/pull/30805#issuecomment-747179899,
    doc `spark.sql.parser.quotedRegexColumnNames` since  we need user know about this in doc and it's useful.
    
    ![image](https://user-images.githubusercontent.com/46485123/103656543-afa4aa80-4fa3-11eb-8cd3-a9d1b87a3489.png)
    ![image](https://user-images.githubusercontent.com/46485123/103656551-b2070480-4fa3-11eb-9ce7-95cc424242a6.png)
    
    ### Why are the changes needed?
    Complete doc
    
    ### Does this PR introduce _any_ user-facing change?
    No
    
    ### How was this patch tested?
    Not need
    
    Closes #30816 from AngersZhuuuu/SPARK-33818.
    
    Authored-by: angerszhu <an...@gmail.com>
    Signed-off-by: Dongjoon Hyun <dh...@apple.com>
    (cherry picked from commit 9b54da490d55d8c12e0a6b2b4b6e3a2d5b6bed86)
    Signed-off-by: Dongjoon Hyun <dh...@apple.com>
---
 docs/sql-ref-syntax-qry-select.md | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/docs/sql-ref-syntax-qry-select.md b/docs/sql-ref-syntax-qry-select.md
index bac7c2b..5820a5c 100644
--- a/docs/sql-ref-syntax-qry-select.md
+++ b/docs/sql-ref-syntax-qry-select.md
@@ -41,7 +41,7 @@ select_statement [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select_stat
 
 While `select_statement` is defined as
 ```sql
-SELECT [ hints , ... ] [ ALL | DISTINCT ] { named_expression [ , ... ] }
+SELECT [ hints , ... ] [ ALL | DISTINCT ] { [ named_expression | regex_column_names ] [ , ... ] }
     FROM { from_item [ , ... ] }
     [ PIVOT clause ]
     [ LATERAL VIEW clause ] [ ... ] 
@@ -151,6 +151,18 @@ SELECT [ hints , ... ] [ ALL | DISTINCT ] { named_expression [ , ... ] }
 
      Specifies aliases for one or more source window specifications. The source window specifications can
      be referenced in the widow definitions in the query.
+     
+* **regex_column_names**
+
+     When `spark.sql.parser.quotedRegexColumnNames` is true, quoted identifiers (using backticks) in `SELECT`
+     statement are interpreted as regular expressions and `SELECT` statement can take regex-based column specification.
+     For example, below SQL will only take column `c`:
+
+     ```sql
+     SELECT `(a|b)?+.+` FROM (
+       SELECT 1 as a, 2 as b, 3 as c
+     )
+     ```
 
 ### Related Statements
 


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