[ASTERIXDB-2815][COMP] DISTINCT in subquery gives wrong result
- user model changes: no
- storage format changes: no
- interface changes: no
Details:
- Fix DISTINCT operator handling during subplan removal
- Added testcases
Change-Id: Idfe0aa09faba9bdad0c9c71e96d1facf07f401c0
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb/+/9585
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Ali Alsuliman <ali.al.solaiman@gmail.com>
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/RemoveLeftOuterUnnestForLeftOuterJoinRule.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/RemoveLeftOuterUnnestForLeftOuterJoinRule.java
index 364816b..775a1df 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/RemoveLeftOuterUnnestForLeftOuterJoinRule.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/RemoveLeftOuterUnnestForLeftOuterJoinRule.java
@@ -91,7 +91,8 @@
Triple<Boolean, ILogicalExpression, ILogicalExpression> checkGbyResult =
checkUnnestAndGby(outerUnnest, gbyOperator);
// The argument for listify and not(is-missing(...)) check should be variables.
- if (!isVariableReference(checkGbyResult.second) || !isVariableReference(checkGbyResult.third)) {
+ if (!checkGbyResult.first || checkGbyResult.second == null || !isVariableReference(checkGbyResult.second)
+ || checkGbyResult.third == null || !isVariableReference(checkGbyResult.third)) {
return false;
}
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java
index 78c4c5e..f7cbb9d 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java
@@ -626,10 +626,11 @@
@Override
public ILogicalOperator visitDistinctOperator(DistinctOperator op, Void arg) throws AlgebricksException {
visitSingleInputOperator(op);
- List<LogicalVariable> distinctVarList = op.getDistinctByVarList();
for (LogicalVariable keyVar : correlatedKeyVars) {
- if (!distinctVarList.contains(keyVar)) {
- distinctVarList.add(keyVar);
+ if (!op.isDistinctByVar(keyVar)) {
+ VariableReferenceExpression keyVarRef = new VariableReferenceExpression(keyVar);
+ keyVarRef.setSourceLocation(op.getSourceLocation());
+ op.getExpressions().add(new MutableObject<>(keyVarRef));
}
}
context.computeAndSetTypeEnvironmentForOperator(op);
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineLeftNtsInSubplanJoinFlatteningVisitor.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineLeftNtsInSubplanJoinFlatteningVisitor.java
index 12596ff..8326f85 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineLeftNtsInSubplanJoinFlatteningVisitor.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineLeftNtsInSubplanJoinFlatteningVisitor.java
@@ -361,10 +361,11 @@
if (!rewritten || !underJoin) {
return op;
}
- List<LogicalVariable> distinctVarList = op.getDistinctByVarList();
for (LogicalVariable keyVar : liveVarsFromSubplanInput) {
- if (!distinctVarList.contains(keyVar)) {
- distinctVarList.add(keyVar);
+ if (!op.isDistinctByVar(keyVar)) {
+ VariableReferenceExpression keyVarRef = new VariableReferenceExpression(keyVar);
+ keyVarRef.setSourceLocation(op.getSourceLocation());
+ op.getExpressions().add(new MutableObject<>(keyVarRef));
}
}
context.computeAndSetTypeEnvironmentForOperator(op);
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/SubplanSpecialFlatteningCheckVisitor.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/SubplanSpecialFlatteningCheckVisitor.java
index 288b01a..a0bb4b6 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/SubplanSpecialFlatteningCheckVisitor.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/SubplanSpecialFlatteningCheckVisitor.java
@@ -220,7 +220,7 @@
@Override
public Boolean visitDistinctOperator(DistinctOperator op, Void arg) throws AlgebricksException {
- return visitInputs(op);
+ return visitTupleDiscardingOperator(op);
}
@Override
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815.sqlpp b/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815.sqlpp
new file mode 100644
index 0000000..9fd4e02
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815.sqlpp
@@ -0,0 +1,43 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+drop dataverse test if exists;
+create dataverse test;
+
+use test;
+
+create type t1 as {
+ _id: uuid
+};
+
+create dataset RawTweet(t1) primary key _id autogenerated;
+
+create dataset Evidence(t1) primary key _id autogenerated;
+
+create dataset Verification(t1) primary key _id autogenerated;
+
+select t.id, urls
+from RawTweet t
+let urls = (
+ select distinct value e.url
+ from Verification v, v.evidence ve, Evidence e
+ where t.id = v.tweet_id and ve = e.ev_id
+)
+where array_count(urls) > 2
+order by t.id;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815.plan
new file mode 100644
index 0000000..363b2bd
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815.plan
@@ -0,0 +1,74 @@
+-- DISTRIBUTE_RESULT |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ASSIGN |PARTITIONED|
+ -- SORT_MERGE_EXCHANGE [$$75(ASC) ] |PARTITIONED|
+ -- STABLE_SORT [$$75(ASC)] |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- STREAM_SELECT |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- PRE_CLUSTERED_GROUP_BY[$$70] |PARTITIONED|
+ {
+ -- AGGREGATE |LOCAL|
+ -- STREAM_SELECT |LOCAL|
+ -- NESTED_TUPLE_SOURCE |LOCAL|
+ }
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- HYBRID_HASH_JOIN [$$70][$$82] |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ASSIGN |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- REPLICATE |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ASSIGN |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- DATASOURCE_SCAN (test.RawTweet) |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- EMPTY_TUPLE_SOURCE |PARTITIONED|
+ -- HASH_PARTITION_EXCHANGE [$$82] |PARTITIONED|
+ -- ASSIGN |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- PRE_SORTED_DISTINCT_BY |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- STABLE_SORT [$$62(ASC), $$82(ASC)] |PARTITIONED|
+ -- HASH_PARTITION_EXCHANGE [$$62, $$82] |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- HYBRID_HASH_JOIN [$$ve][$$73] |PARTITIONED|
+ -- HASH_PARTITION_EXCHANGE [$$ve] |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- UNNEST |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- HYBRID_HASH_JOIN [$$80][$$76] |PARTITIONED|
+ -- HASH_PARTITION_EXCHANGE [$$80] |PARTITIONED|
+ -- REPLICATE |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ASSIGN |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- DATASOURCE_SCAN (test.RawTweet) |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- EMPTY_TUPLE_SOURCE |PARTITIONED|
+ -- HASH_PARTITION_EXCHANGE [$$76] |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ASSIGN |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- DATASOURCE_SCAN (test.Verification) |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- EMPTY_TUPLE_SOURCE |PARTITIONED|
+ -- HASH_PARTITION_EXCHANGE [$$73] |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ASSIGN |PARTITIONED|
+ -- STREAM_PROJECT |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- DATASOURCE_SCAN (test.Evidence) |PARTITIONED|
+ -- ONE_TO_ONE_EXCHANGE |PARTITIONED|
+ -- EMPTY_TUPLE_SOURCE |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.1.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.1.ddl.sqlpp
new file mode 100644
index 0000000..7de1e4e
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.1.ddl.sqlpp
@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+drop dataverse test if exists;
+create dataverse test;
+
+use test;
+
+create type t1 as {
+ _id: uuid
+};
+
+create dataset RawTweet(t1) primary key _id autogenerated;
+
+create dataset Evidence(t1) primary key _id autogenerated;
+
+create dataset Verification(t1) primary key _id autogenerated;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.2.update.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.2.update.sqlpp
new file mode 100644
index 0000000..29a4ff6
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.2.update.sqlpp
@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+
+insert into RawTweet ([
+ { "id" : 1, "full_text": "text_1" }, -- total evidence : 2
+ { "id" : 2, "full_text": "text_2" }, -- total evidence : 4 (*) -- satisfies the query
+ { "id" : 3, "full_text": "text_3" }, -- total evidence : 0
+ { "id" : 4, "full_text": "text_4" }, -- total evidence : 6 (*) -- satisfies the query
+ { "id" : 5, "full_text": "text_5" } -- total evidence : 1
+ ]);
+
+insert into Verification ([
+ { "ver_id" : 1001, "tweet_id": 1, "evidence": [ 2001, 2002 ] },
+ { "ver_id" : 1002, "tweet_id": 2, "evidence": [ 2003, 2004 ] },
+ { "ver_id" : 1003, "tweet_id": 2, "evidence": [ 2009, 2010 ] },
+ { "ver_id" : 1004, "tweet_id": 4, "evidence": [ 2004, 2005, 2006 ] },
+ { "ver_id" : 1005, "tweet_id": 4, "evidence": [ 2007, 2008, 2009 ] },
+ { "ver_id" : 1006, "tweet_id": 5, "evidence": [ 2001 ] }
+]);
+
+insert into Evidence ([
+ { "ev_id" : 2001, "url": "http://example.org/2001" },
+ { "ev_id" : 2002, "url": "http://example.org/2002" },
+ { "ev_id" : 2003, "url": "http://example.org/2003" },
+ { "ev_id" : 2004, "url": "http://example.org/2004" },
+ { "ev_id" : 2005, "url": "http://example.org/2005" },
+ { "ev_id" : 2006, "url": "http://example.org/2006" },
+ { "ev_id" : 2007, "url": "http://example.org/2007" },
+ { "ev_id" : 2008, "url": "http://example.org/2008" },
+ { "ev_id" : 2009, "url": "http://example.org/2009" },
+ { "ev_id" : 2010, "url": "http://example.org/2010" }
+]);
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.3.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.3.query.sqlpp
new file mode 100644
index 0000000..9072bb7
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.3.query.sqlpp
@@ -0,0 +1,30 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+
+select t.id, array_sort(urls) urls
+from RawTweet t
+let urls = (
+ select distinct value e.url
+ from Verification v, v.evidence ve, Evidence e
+ where t.id = v.tweet_id and ve = e.ev_id
+)
+where array_count(urls) > 2
+order by t.id;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.3.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.3.adm
new file mode 100644
index 0000000..448de2d
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.3.adm
@@ -0,0 +1,2 @@
+{ "urls": [ "http://example.org/2003", "http://example.org/2004", "http://example.org/2009", "http://example.org/2010" ], "id": 2 }
+{ "urls": [ "http://example.org/2004", "http://example.org/2005", "http://example.org/2006", "http://example.org/2007", "http://example.org/2008", "http://example.org/2009" ], "id": 4 }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
index bca453d..813af62 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
@@ -10400,6 +10400,11 @@
<output-dir compare="Text">query-ASTERIXDB-1674</output-dir>
</compilation-unit>
</test-case>
+ <test-case FilePath="subquery">
+ <compilation-unit name="query-ASTERIXDB-2815">
+ <output-dir compare="Text">query-ASTERIXDB-2815</output-dir>
+ </compilation-unit>
+ </test-case>
</test-group>
<test-group name="subset-collection">
<test-case FilePath="subset-collection">
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/DistinctOperator.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/DistinctOperator.java
index 9ac6659..673d80d 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/DistinctOperator.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/DistinctOperator.java
@@ -52,8 +52,8 @@
@Override
public void recomputeSchema() {
- schema = new ArrayList<LogicalVariable>();
- schema.addAll(this.getDistinctByVarList());
+ schema = new ArrayList<>();
+ schema.addAll(getDistinctByVarList());
List<LogicalVariable> inputSchema = inputs.get(0).getValue().getSchema();
for (LogicalVariable var : inputSchema) {
if (!schema.contains(var)) {
@@ -66,13 +66,12 @@
public VariablePropagationPolicy getVariablePropagationPolicy() {
return new VariablePropagationPolicy() {
@Override
- public void propagateVariables(IOperatorSchema target, IOperatorSchema... sources)
- throws AlgebricksException {
- /** make sure distinct key vars laid-out first */
+ public void propagateVariables(IOperatorSchema target, IOperatorSchema... sources) {
+ /* make sure distinct key vars laid-out first */
for (LogicalVariable keyVar : getDistinctByVarList()) {
target.addVariable(keyVar);
}
- /** add other source vars */
+ /* add other source vars */
for (IOperatorSchema srcSchema : sources) {
for (LogicalVariable srcVar : srcSchema)
if (target.findVariable(srcVar) < 0) {
@@ -105,7 +104,7 @@
}
public List<LogicalVariable> getDistinctByVarList() {
- List<LogicalVariable> varList = new ArrayList<LogicalVariable>(expressions.size());
+ List<LogicalVariable> varList = new ArrayList<>(expressions.size());
for (Mutable<ILogicalExpression> eRef : expressions) {
ILogicalExpression e = eRef.getValue();
if (e.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
@@ -121,7 +120,7 @@
ILogicalExpression e = eRef.getValue();
if (e.getExpressionTag() == LogicalExpressionTag.VARIABLE) {
VariableReferenceExpression v = (VariableReferenceExpression) e;
- if (v.getVariableReference() == var) {
+ if (v.getVariableReference().equals(var)) {
return true;
}
}
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/visitors/CardinalityInferenceVisitor.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/visitors/CardinalityInferenceVisitor.java
index 54cbcd0..f68638d 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/visitors/CardinalityInferenceVisitor.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/logical/visitors/CardinalityInferenceVisitor.java
@@ -244,6 +244,8 @@
@Override
public Long visitDistinctOperator(DistinctOperator op, Void arg) throws AlgebricksException {
+ // DISTINCT cannot reduce cardinality from ONE to ZERO_OR_ONE, or from ONE_GROUP to ZERO_OR_ONE_GROUP
+ // therefore we don't need to call adjustCardinalityForTupleReductionOperator() here.
return op.getInputs().get(0).getValue().accept(this, arg);
}