[jira] [Created] (SPARK-27596) The JDBC 'query' option doesn't work for Oracle database

["Xiao Li (JIRA)" <ji...@apache.org>]

Xiao Li created SPARK-27596:
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             Summary: The JDBC 'query' option doesn't work for Oracle database
                 Key: SPARK-27596
                 URL: https://issues.apache.org/jira/browse/SPARK-27596
             Project: Spark
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 2.4.2
            Reporter: Xiao Li
            Assignee: Dilip Biswal


For the JDBC option `query`, we use the identifier name to start with underscore: s"(${subquery}) __SPARK_GEN_JDBC_SUBQUERY_NAME_${curId.getAndIncrement()}". This is not supported by Oracle. 

The Oracle doesn't seem to support identifier name to start with non-alphabet character (unless it is quoted) and has length restrictions as well.
https://docs.oracle.com/cd/B19306_01/server.102/b14200/sql_elements008.htm

{code:java}
Nonquoted identifiers must begin with an alphabetic character from your database character set. Quoted identifiers can begin with any character as per below documentation - 
Nonquoted identifiers can contain only alphanumeric characters from your database character set and the underscore (_), dollar sign ($), and pound sign (#). Database links can also contain periods (.) and "at" signs (@). Oracle strongly discourages you from using $ and # in nonquoted identifiers.
{code}

The alias name '_SPARK_GEN_JDBC_SUBQUERY_NAME<int value>' should be fixed to remove "__" prefix ( or make it quoted.not sure if it may impact other sources) to make it work for Oracle. Also the length should be limited as it is hitting below error on removing the prefix.

{code:java}
java.sql.SQLSyntaxErrorException: ORA-00972: identifier is too long 
{code}

It can be verified using below sqlfiddle link.

http://www.sqlfiddle.com/#!4/9bbe9a/10050





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