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## What changes were proposed in this pull request? Currently, function `substr/substring`'s usage is like `substring(string_expression, n1 [,n2])`. But, the ANSI SQL defined the pattern for substr/substring is like `SUBSTRING(str FROM n1 [FOR n2])`. This gap makes some inconvenient when we switch to the SparkSQL. - ANSI SQL-92: http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt Below are the mainly DB engines to support the ANSI standard for substring. - PostgreSQL https://www.postgresql.org/docs/9.1/functions-string.html - MySQL https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_substring - Redshift https://docs.aws.amazon.com/redshift/latest/dg/r_SUBSTRING.html - Teradata https://docs.teradata.com/reader/756LNiPSFdY~4JcCCcR5Cw/XnePye0Cwexw6Pny_qnxVA **Oracle, SQL Server, Hive, Presto don't have this additional syntax.** ## How was this patch tested? Pass the Jenkins with the updated test cases. Closes #24802 from lipzhu/SPARK-27949. Authored-by: Zhu, Lipeng <lipzhu@ebay.com> Signed-off-by: Dongjoon Hyun <dhyun@apple.com> |
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