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From tarmstr...@apache.org
Subject [14/14] incubator-impala git commit: IMPALA-4335: Don't send 0-row batches to clients
Date Sat, 22 Oct 2016 05:33:41 GMT
IMPALA-4335: Don't send 0-row batches to clients

This patch restores some behaviour from pre-IMPALA-2905 where we would
not send 0-row batches to the client. Although 0-row batches are legal,
they're not very useful for clients to receive (and clients may not
correctly process them).

No query was found which reliably produced 0-row batches, so no test is
added.

Change-Id: I7d339c1f9a55d9d75fb0e97d16b3176cc34f2171
Reviewed-on: http://gerrit.cloudera.org:8080/4787
Reviewed-by: Henry Robinson <henry@cloudera.com>
Tested-by: Internal Jenkins


Project: http://git-wip-us.apache.org/repos/asf/incubator-impala/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-impala/commit/48085274
Tree: http://git-wip-us.apache.org/repos/asf/incubator-impala/tree/48085274
Diff: http://git-wip-us.apache.org/repos/asf/incubator-impala/diff/48085274

Branch: refs/heads/master
Commit: 48085274fa8ae57453477db21dae0e53eae6b766
Parents: e39f167
Author: Henry Robinson <henry@cloudera.com>
Authored: Fri Oct 21 15:38:34 2016 -0700
Committer: Internal Jenkins <cloudera-hudson@gerrit.cloudera.org>
Committed: Sat Oct 22 04:49:39 2016 +0000

----------------------------------------------------------------------
 be/src/exec/plan-root-sink.cc | 8 ++++++--
 be/src/runtime/coordinator.h  | 1 -
 2 files changed, 6 insertions(+), 3 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/48085274/be/src/exec/plan-root-sink.cc
----------------------------------------------------------------------
diff --git a/be/src/exec/plan-root-sink.cc b/be/src/exec/plan-root-sink.cc
index bd73953..c728f4a 100644
--- a/be/src/exec/plan-root-sink.cc
+++ b/be/src/exec/plan-root-sink.cc
@@ -84,7 +84,11 @@ void ValidateCollectionSlots(const RowDescriptor& row_desc, RowBatch*
batch) {
 Status PlanRootSink::Send(RuntimeState* state, RowBatch* batch) {
   ValidateCollectionSlots(row_desc_, batch);
   int current_batch_row = 0;
-  do {
+
+  // Don't enter the loop if batch->num_rows() == 0; no point triggering the consumer
with
+  // 0 rows to return. Be wary of ever returning 0-row batches to the client; some poorly
+  // written clients may not cope correctly with them. See IMPALA-4335.
+  while (current_batch_row < batch->num_rows()) {
     unique_lock<mutex> l(lock_);
     while (results_ == nullptr && !consumer_done_) sender_cv_.wait(l);
     if (consumer_done_ || batch == nullptr) {
@@ -114,7 +118,7 @@ Status PlanRootSink::Send(RuntimeState* state, RowBatch* batch) {
     results_ = nullptr;
     ExprContext::FreeLocalAllocations(output_expr_ctxs_);
     consumer_cv_.notify_all();
-  } while (current_batch_row < batch->num_rows());
+  }
   return Status::OK();
 }
 

http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/48085274/be/src/runtime/coordinator.h
----------------------------------------------------------------------
diff --git a/be/src/runtime/coordinator.h b/be/src/runtime/coordinator.h
index f73cf42..9904def 100644
--- a/be/src/runtime/coordinator.h
+++ b/be/src/runtime/coordinator.h
@@ -15,7 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-
 #ifndef IMPALA_RUNTIME_COORDINATOR_H
 #define IMPALA_RUNTIME_COORDINATOR_H
 


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