c66d64b3df
#### What changes were proposed in this pull request? This PR enhances the TRIM function support in Spark SQL by allowing the specification of trim characters set. Below is the SQL syntax : ``` SQL <trim function> ::= TRIM <left paren> <trim operands> <right paren> <trim operands> ::= [ [ <trim specification> ] [ <trim character set> ] FROM ] <trim source> <trim source> ::= <character value expression> <trim specification> ::= LEADING | TRAILING | BOTH <trim character set> ::= <characters value expression> ``` or ``` SQL LTRIM (source-exp [, trim-exp]) RTRIM (source-exp [, trim-exp]) ``` Here are the documentation link of support of this feature by other mainstream databases. - **Oracle:** [TRIM function](http://docs.oracle.com/cd/B28359_01/olap.111/b28126/dml_functions_2126.htm#OLADM704) - **DB2:** [TRIM scalar function](https://www.ibm.com/support/knowledgecenter/en/SSMKHH_10.0.0/com.ibm.etools.mft.doc/ak05270_.htm) - **MySQL:** [Trim function](http://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_trim) - **Oracle:** [ltrim](https://docs.oracle.com/cd/B28359_01/olap.111/b28126/dml_functions_2018.htm#OLADM594) - **DB2:** [ltrim](https://www.ibm.com/support/knowledgecenter/en/SSEPEK_11.0.0/sqlref/src/tpc/db2z_bif_ltrim.html) This PR is to implement the above enhancement. In the implementation, the design principle is to keep the changes to the minimum. Also, the exiting trim functions (which handles a special case, i.e., trimming space characters) are kept unchanged for performane reasons. #### How was this patch tested? The unit test cases are added in the following files: - UTF8StringSuite.java - StringExpressionsSuite.scala - sql/SQLQuerySuite.scala - StringFunctionsSuite.scala Author: Kevin Yu <qyu@us.ibm.com> Closes #12646 from kevinyu98/spark-14878. |
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