IMPALA-4042: Preserve root types when substituting grouping exprs

In case of count(distinct), FunctionCallExpr.analyze() changes type
for "NULL" into "BOOLEAN" to make sure that BE doesn't see any
"NULL_TYPE" exprs. In the meantime, Expr substitution, happening in
Expr.substituteImpl() reverts this change back to original type,
"NULL_TYPE".

This causes an issue when AggregateInfo.checkConsistency() performs
precondition check where slot types from
AggregateInfo.outputTupleDesc_ should be matched with the types from
AggregateInfo.groupingExpr_. The slot type shows "BOOLEAN" while type
from groupingExpr_ is "NULL_TYPE", which makes the precondition fail
and throws an exception.

To resolve the issue, preserveRootType is set to true when
Expr.substituteList() gets called in AggregateInfo.substitute()

Change-Id: Icf3b4511234e473e5b9548fbf3e97f333c9980f1
(cherry picked from commit b17785b4890bedd1c825140ce3c48cd7d9734295)
Reviewed-on: http://gerrit.cloudera.org:8080/4600
Reviewed-by: Alex Behm <[email protected]>
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/112ff68e
Tree: http://git-wip-us.apache.org/repos/asf/incubator-impala/tree/112ff68e
Diff: http://git-wip-us.apache.org/repos/asf/incubator-impala/diff/112ff68e

Branch: refs/heads/master
Commit: 112ff68eddde5e29bacf31170741ee7746c0cbb8
Parents: e659337
Author: Yonghyun Hwang <[email protected]>
Authored: Fri Sep 30 16:12:46 2016 -0700
Committer: Internal Jenkins <[email protected]>
Committed: Wed Oct 5 03:04:17 2016 +0000

----------------------------------------------------------------------
 .../apache/impala/analysis/AggregateInfo.java   |  4 +++-
 .../queries/PlannerTest/distinct.test           | 22 ++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/112ff68e/fe/src/main/java/org/apache/impala/analysis/AggregateInfo.java
----------------------------------------------------------------------
diff --git a/fe/src/main/java/org/apache/impala/analysis/AggregateInfo.java 
b/fe/src/main/java/org/apache/impala/analysis/AggregateInfo.java
index 29b80ef..8590872 100644
--- a/fe/src/main/java/org/apache/impala/analysis/AggregateInfo.java
+++ b/fe/src/main/java/org/apache/impala/analysis/AggregateInfo.java
@@ -335,7 +335,9 @@ public class AggregateInfo extends AggregateInfoBase {
    */
   public void substitute(ExprSubstitutionMap smap, Analyzer analyzer)
       throws InternalException {
-    groupingExprs_ = Expr.substituteList(groupingExprs_, smap, analyzer, 
false);
+
+    // Preserve the root type for NULL literals.
+    groupingExprs_ = Expr.substituteList(groupingExprs_, smap, analyzer, true);
     LOG.trace("AggInfo: grouping_exprs=" + Expr.debugString(groupingExprs_));
 
     // The smap in this case should not substitute the aggs themselves, only

http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/112ff68e/testdata/workloads/functional-planner/queries/PlannerTest/distinct.test
----------------------------------------------------------------------
diff --git 
a/testdata/workloads/functional-planner/queries/PlannerTest/distinct.test 
b/testdata/workloads/functional-planner/queries/PlannerTest/distinct.test
index 15f1d59..e5f3bce 100644
--- a/testdata/workloads/functional-planner/queries/PlannerTest/distinct.test
+++ b/testdata/workloads/functional-planner/queries/PlannerTest/distinct.test
@@ -473,3 +473,25 @@ select * from (select count(distinct int_col) cd from 
functional.alltypes group
 00:SCAN HDFS [functional.alltypes]
    partitions=24/24 files=24 size=478.45KB
 ====
+# IMPALA-4042: count(distinct NULL) fails on a view
+select count(distinct null) from functional.alltypes_view
+---- DISTRIBUTEDPLAN
+06:AGGREGATE [FINALIZE]
+|  output: count:merge(NULL)
+|
+05:EXCHANGE [UNPARTITIONED]
+|
+02:AGGREGATE
+|  output: count(NULL)
+|
+04:AGGREGATE
+|  group by: NULL
+|
+03:EXCHANGE [HASH(NULL)]
+|
+01:AGGREGATE [STREAMING]
+|  group by: NULL
+|
+00:SCAN HDFS [functional.alltypes]
+   partitions=24/24 files=24 size=478.45KB
+====

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