[
https://issues.apache.org/jira/browse/SPARK-9078?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Apache Spark reassigned SPARK-9078:
-----------------------------------
Assignee: Apache Spark
> Use of non-standard LIMIT keyword in JDBC tableExists code
> ----------------------------------------------------------
>
> Key: SPARK-9078
> URL: https://issues.apache.org/jira/browse/SPARK-9078
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 1.3.1, 1.4.0
> Reporter: Robert Beauchemin
> Assignee: Apache Spark
> Priority: Minor
>
> tableExists in
> spark/sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcUtils.scala uses
> non-standard SQL (specifically, the LIMIT keyword) to determine whether a
> table exists in a JDBC data source. This will cause an exception in many/most
> JDBC databases that doesn't support LIMIT keyword. See
> http://stackoverflow.com/questions/1528604/how-universal-is-the-limit-statement-in-sql
> To check for table existence or an exception, it could be recrafted around
> "select 1 from $table where 0 = 1" which isn't the same (it returns an empty
> resultset rather than the value '1'), but would support more data sources and
> also support empty tables. Arguably ugly and possibly queries every row on
> sources that don't support constant folding, but better than failing on JDBC
> sources that don't support LIMIT.
> Perhaps "supports LIMIT" could be a field in the JdbcDialect class for
> databases that support keyword this to override. The ANSI standard is (OFFSET
> and) FETCH.
> The standard way to check for table existence would be to use
> information_schema.tables which is a SQL standard but may not work for other
> JDBC data sources that support SQL, but not the information_schema. The JDBC
> DatabaseMetaData interface provides getSchemas() that allows checking for
> the information_schema in drivers that support it.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
