Author: Joe McDonnell <firstname.lastname@example.org>
Date: Fri Mar 3 17:47:23 2017 -0800
IMPALA-4996: Single-threaded KuduScanNode
This introduces KuduScanNodeMt, the single-threaded version
of KuduScanNode that materializes the tuples in GetNext().
KuduScanNodeMt is enabled by the same condition as
HdfsScanNodeMt: mt_dop is greater than or equal to 1.
To share code between the two implementations, KuduScanNode
and KuduScanNodeMt are now subclasses of KuduScanNodeBase,
which implements the shared code. The KuduScanner is
minimally impacted, as it already had the required GetNext
Since the KuduClient is a heavy-weight object, it is now
shared at the QueryState level. We try to share the
KuduClient as much as possible, but there are times when
the KuduClient cannot be shared. Each Kudu table has
master addresses stored in the Hive Metastore. We only
share KuduClients for tables that have an identical value
for the master addresses. In the ideal case, every Kudu
table will have the same value, but there is no explicit
guarantee of this.
The testing for this is a modified version of
kudu-scan-node.test run with various mt_dop values.
Reviewed-by: Marcel Kornacker <email@example.com>
Tested-by: Impala Public Jenkins