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Posted to jira@arrow.apache.org by "Micah Kornfield (Jira)" <ji...@apache.org> on 2021/01/04 22:31:00 UTC

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

     [ https://issues.apache.org/jira/browse/ARROW-10492?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Micah Kornfield resolved ARROW-10492.
-------------------------------------
    Fix Version/s: 3.0.0
       Resolution: Fixed

Issue resolved by pull request 8597
[https://github.com/apache/arrow/pull/8597]

> [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
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.0.0
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> 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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