[jira] [Created] (ARROW-10492) [Java][JDBC] Allow users to config the mapping between SQL types and Arrow types

["Liya Fan (Jira)" <ji...@apache.org>]

Liya Fan created ARROW-10492:
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             Summary: [Java][JDBC] Allow users to config the mapping between SQL types and Arrow types
                 Key: ARROW-10492
                 URL: https://issues.apache.org/jira/browse/ARROW-10492
             Project: Apache Arrow
          Issue Type: Improvement
          Components: Java
            Reporter: Liya Fan
            Assignee: Liya Fan


According to the current implementation of JDBC adapter, the conversion between SQL types and Arrow types is hard-coded. This will cause some problems in practice:
 # The appropriate conversion may vary for different databases. For example, for SQL Server, type {{real}} corresponds to 4 byte floating point values ([https://docs.microsoft.com/en-us/sql/t-sql/data-types/float-and-real-transact-sql?view=sql-server-ver15),] whereas for SQLite, \{{real}} corresponds to 8 byte floating point values ([https://www.sqlitetutorial.net/sqlite-data-types/).] If the maping is not right, some extra conversion would happen, which can impact performance severely. 
 # Our current implementation determines the type conversion solely based on the type ID. However, the appropriate conversion may also depend some other information, like precision and scale. For example, for {{FLOAT(n)}}, it should correspond to 4 byte floating point values, if n <= 24, otherwise, it should correspond to 8 byte floating point values.  

To address the problems, we should allow users to customize the conversion between SQL and Arrow types. 



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