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https://issues.apache.org/jira/browse/ARROW-16035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17534049#comment-17534049
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Jonathan Swenson commented on ARROW-16035:
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Thanks [~toddfarmer] I didn't realize that isAfterLast is also optional. I now
see that using isAfterLast was discussed back when it was added as well.
Avoiding using these optional features is likely desirable, but this doesn't
add any _extra_ incompatibility.
I'm looking into using the JDBC -> arrow functionality with a variety of
different JDBC drivers in the future, but I'm currently not aware of which JDBC
drivers implement all of these optional features.
I believe that the "empty" vector schema root makes sense as it can also return
schema metadata about the (empty) result set which mirrors the JDBC ResultSet
metadata associated with running a SQL query JDBC query.
> [Java] Arrow to JDBC ArrowVectorIterator with does not terminate with empty
> result set
> --------------------------------------------------------------------------------------
>
> Key: ARROW-16035
> URL: https://issues.apache.org/jira/browse/ARROW-16035
> Project: Apache Arrow
> Issue Type: Bug
> Components: Java
> Affects Versions: 7.0.0
> Reporter: Jonathan Swenson
> Assignee: Todd Farmer
> Priority: Major
> Labels: pull-request-available
> Fix For: 8.0.0
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> Using an ArrowVectorIterator built from a JDBC Result Set that is empty
> causes the iterator to never terminate.
> {code:java}
> ArrowVectorIterator iterator =
> JdbcToArrow.sqlToArrowVectorIterator(conn.createStatement()
> .executeQuery("select 1 from table1 where false"), config); {code}
>
> It appears as though this is due to the implementation of the
> [hasNext()|https://github.com/apache/arrow/blob/master/java/adapter/jdbc/src/main/java/org/apache/arrow/adapter/jdbc/ArrowVectorIterator.java#L158]
> method.
> The expectation is that the `isAfterLast()` method on a JDBC result set
> return true when the result set is empty. However, according to the [JDBC
> documentation|https://docs.oracle.com/en/java/javase/11/docs/api/java.sql/java/sql/ResultSet.html#isAfterLast()]
> it will always return false when the result set is empty.
> {quote}Returns:{{{}true{}}} if the cursor is after the last row; {{false}} if
> the cursor is at any other position or the result set contains no rows
> {quote}
>
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