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https://issues.apache.org/jira/browse/DRILL-2288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14632614#comment-14632614
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Daniel Barclay (Drill) edited comment on DRILL-2288 at 7/25/15 7:54 PM:
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Investigation notes:
- Is not a JDBC problem--seems to be an INFORMATION_SCHEMA/ischema problem.
- Has something to do with ischema filtering--whether metadata is missing or
not depends on whether having zero rows was caused by mismatching one of the
specially filtered (pushed-down?) fields (e.g., TABLE_SCHEMA and TABLE_NAME for
COLUMNS) or not, respectively.
- Seems that a downstream schema is derived from the set of value vectors
(etc.) at some point, but that set is empty sometimes when there are no rows
(when no values have been written to vectors/vector container?).
- Does seem to be in INFORMATION_SCHEMA plug-in: It doesn't seem to use
PojoDataType as system-tables plug-in does.
- NOT specific to INFORMATION_SCHEMA plug-in: Underlying problem seems shared
with system-table plugin. (Cloning sys.version to return zero rows exhibits
the same symptom.)
- Seems that something in both plug-ins (scans? scan batches?) fails to pass
the schema directly, only setting the schema implicitly--and only when there's
at least one row to set up value vectors.
was (Author: dsbos):
Investigation notes:
- Is not a JDBC problem--seems to be an INFORMATION_SCHEMA/ischema problem.
- Has something to do with ischema filtering--whether metadata is missing or
not depends on whether having zero rows was caused by mismatching one of the
specially filtered (pushed-down?) fields (e.g., TABLE_SCHEMA and TABLE_NAME for
COLUMNS) or not, respectively.
- Seems that a downstream schema is derived from the set of value vectors
(etc.) at some point, but that set is empty sometimes when there are no rows
(when no values have been written to vectors/vector container?).
- Does seem to be in INFORMATION_SCHEMA plug-in: It doesn't seem to use
PojoDataType as system-tables plug-in does.
> result set metadata not set for zero-row result
> (DatabaseMetaData.getColumns(...))
> -----------------------------------------------------------------------------------
>
> Key: DRILL-2288
> URL: https://issues.apache.org/jira/browse/DRILL-2288
> Project: Apache Drill
> Issue Type: Bug
> Components: Storage - Information Schema
> Reporter: Daniel Barclay (Drill)
> Assignee: Daniel Barclay (Drill)
> Fix For: 1.2.0
>
> Attachments: Drill2288NoResultSetMetadataWhenZeroRowsTest.java
>
>
> The ResultSetMetaData object from getMetadata() of a ResultSet is not set up
> (getColumnCount() returns zero, and trying to access any other metadata
> throws IndexOutOfBoundsException) for a result set with zero rows, at least
> for one from DatabaseMetaData.getColumns(...).
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