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https://issues.apache.org/jira/browse/SPARK-22441?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16239275#comment-16239275
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Tor Myklebust commented on SPARK-22441:
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> In MySQL, even desc a table with a column defined as REAL, it will show
> double as its type. And in JDBC the return SQL type is DOUBLE, and the type
> name is also DOUBLE. So it doesn't break the specification. The spec only
> discusses the JDBC types and java types. It doesn't cover the data types
> inside the databases.
OK. I'm not in a position to verify MySQL's behaviour.
> Yes, the real world and the spec are different, such as SPARK-17195
> However, are there any concrete cases related to REAL/FLOAT/DOUBLE that make
> us go against the specification?
If, as you say, this behaviour isn't exhibited by MySQL, then I don't know of
any such concrete cases.
> JDBC REAL type is mapped to Double instead of Float
> ---------------------------------------------------
>
> Key: SPARK-22441
> URL: https://issues.apache.org/jira/browse/SPARK-22441
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.2.0
> Reporter: Hongbo
> Priority: Minor
>
> In [JDBC
> Specification|http://download.oracle.com/otn-pub/jcp/jdbc-4_1-mrel-eval-spec/jdbc4.1-fr-spec.pdf],
> REAL should be mapped to Float.
> But now, it's mapped to Double:
> [https://github.com/apache/spark/blob/bc7ca9786e162e33f29d57c4aacb830761b97221/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JdbcUtils.scala#L220]
> Should it be changed according to the specification?
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