diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/base/RuleCollections.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/base/RuleCollections.java
index e4c35e4..f9aecab 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/base/RuleCollections.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/base/RuleCollections.java
@@ -30,6 +30,7 @@
 import org.apache.asterix.optimizer.rules.AsterixExtractFunctionsFromJoinConditionRule;
 import org.apache.asterix.optimizer.rules.AsterixInlineVariablesRule;
 import org.apache.asterix.optimizer.rules.AsterixIntroduceGroupByCombinerRule;
+import org.apache.asterix.optimizer.rules.AsterixPushAssignBelowUnionAllRule;
 import org.apache.asterix.optimizer.rules.ByNameToByIndexFieldAccessRule;
 import org.apache.asterix.optimizer.rules.CancelUnnestWithNestedListifyRule;
 import org.apache.asterix.optimizer.rules.CheckFilterExpressionTypeRule;
@@ -117,7 +118,6 @@
 import org.apache.hyracks.algebricks.rewriter.rules.IntroduceProjectsRule;
 import org.apache.hyracks.algebricks.rewriter.rules.IsolateHyracksOperatorsRule;
 import org.apache.hyracks.algebricks.rewriter.rules.PullSelectOutOfEqJoin;
-import org.apache.hyracks.algebricks.rewriter.rules.PushAssignBelowUnionAllRule;
 import org.apache.hyracks.algebricks.rewriter.rules.PushGroupByIntoSortRule;
 import org.apache.hyracks.algebricks.rewriter.rules.PushMapOperatorDownThroughProductRule;
 import org.apache.hyracks.algebricks.rewriter.rules.PushNestedOrderByUnderPreSortedGroupByRule;
@@ -330,7 +330,7 @@
     public static final List<IAlgebraicRewriteRule> buildPlanCleanupRuleCollection() {
         List<IAlgebraicRewriteRule> planCleanupRules = new LinkedList<>();
         planCleanupRules.add(new SwitchInnerJoinBranchRule());
-        planCleanupRules.add(new PushAssignBelowUnionAllRule());
+        planCleanupRules.add(new AsterixPushAssignBelowUnionAllRule());
         planCleanupRules.add(new ExtractCommonExpressionsRule());
         planCleanupRules.add(new RemoveRedundantVariablesRule());
         planCleanupRules.add(new PushProjectDownRule());
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/AsterixPushAssignBelowUnionAllRule.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/AsterixPushAssignBelowUnionAllRule.java
new file mode 100644
index 0000000..23ff7c6
--- /dev/null
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/AsterixPushAssignBelowUnionAllRule.java
@@ -0,0 +1,97 @@
+/*
+ * 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.
+ */
+package org.apache.asterix.optimizer.rules;
+
+import java.util.List;
+
+import org.apache.asterix.om.base.AInt32;
+import org.apache.asterix.om.constants.AsterixConstantValue;
+import org.apache.asterix.om.functions.BuiltinFunctions;
+import org.apache.asterix.om.types.ARecordType;
+import org.apache.asterix.om.utils.ConstantExpressionUtil;
+import org.apache.commons.lang3.mutable.Mutable;
+import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
+import org.apache.hyracks.algebricks.common.utils.Triple;
+import org.apache.hyracks.algebricks.core.algebra.base.ILogicalExpression;
+import org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator;
+import org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext;
+import org.apache.hyracks.algebricks.core.algebra.base.LogicalExpressionTag;
+import org.apache.hyracks.algebricks.core.algebra.base.LogicalVariable;
+import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression;
+import org.apache.hyracks.algebricks.core.algebra.expressions.ConstantExpression;
+import org.apache.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression;
+import org.apache.hyracks.algebricks.core.algebra.operators.logical.UnionAllOperator;
+import org.apache.hyracks.algebricks.rewriter.rules.PushAssignBelowUnionAllRule;
+
+public class AsterixPushAssignBelowUnionAllRule extends PushAssignBelowUnionAllRule {
+
+    // modifies field-access-by-index by adjusting the index to match the one in the branch where assign is moved to
+    @Override
+    protected boolean modifyExpression(ILogicalExpression expression, UnionAllOperator unionOp,
+            IOptimizationContext ctx, int inputIndex) throws AlgebricksException {
+        if (expression.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
+            return true; // expressions other than functions need not be modified
+        }
+        AbstractFunctionCallExpression functionCall = (AbstractFunctionCallExpression) expression;
+        List<Mutable<ILogicalExpression>> arguments = functionCall.getArguments();
+        for (int k = 0, size = arguments.size(); k < size; k++) {
+            if (!modifyExpression(arguments.get(k).getValue(), unionOp, ctx, inputIndex)) {
+                return false;
+            }
+        }
+        // return true if any function other than field-access-by-index. otherwise, try to map the index.
+        return !functionCall.getFunctionIdentifier().equals(BuiltinFunctions.FIELD_ACCESS_BY_INDEX)
+                || mapFieldIndex(functionCall, unionOp, ctx, inputIndex);
+    }
+
+    private static boolean mapFieldIndex(AbstractFunctionCallExpression functionCall, UnionAllOperator unionOp,
+            IOptimizationContext ctx, int inputIndex) throws AlgebricksException {
+        // the record variable in the field access should match the output variable from union, i.e. $2.getField
+        ILogicalExpression recordExpr = functionCall.getArguments().get(0).getValue();
+        if (recordExpr.getExpressionTag() != LogicalExpressionTag.VARIABLE) {
+            return false;
+        }
+        Integer fieldIndex = ConstantExpressionUtil.getIntArgument(functionCall, 1);
+        if (fieldIndex == null) {
+            return false;
+        }
+        LogicalVariable recordVar = ((VariableReferenceExpression) recordExpr).getVariableReference();
+        for (Triple<LogicalVariable, LogicalVariable, LogicalVariable> varMap : unionOp.getVariableMappings()) {
+            if (varMap.third.equals(recordVar)) {
+                ARecordType unionType = (ARecordType) ctx.getOutputTypeEnvironment(unionOp).getVarType(varMap.third);
+                ILogicalOperator inputOpToUnion = unionOp.getInputs().get(inputIndex).getValue();
+                ARecordType inputType;
+                if (inputIndex == 0) {
+                    inputType = (ARecordType) ctx.getOutputTypeEnvironment(inputOpToUnion).getVarType(varMap.first);
+                } else {
+                    inputType = (ARecordType) ctx.getOutputTypeEnvironment(inputOpToUnion).getVarType(varMap.second);
+                }
+                String fieldName = unionType.getFieldNames()[fieldIndex];
+                fieldIndex = inputType.getFieldIndex(fieldName);
+                if (fieldIndex < 0) {
+                    return false;
+                }
+                functionCall.getArguments().get(1)
+                        .setValue(new ConstantExpression(new AsterixConstantValue(new AInt32(fieldIndex))));
+                return true;
+            }
+        }
+        return false;
+    }
+}
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.1.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.1.ddl.sqlpp
new file mode 100644
index 0000000..a01b14b
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.1.ddl.sqlpp
@@ -0,0 +1,49 @@
+/*
+ * 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 TinySocial IF EXISTS;
+CREATE DATAVERSE TinySocial;
+USE TinySocial;
+
+CREATE TYPE ChirpUserType AS {
+    screenName: string,
+    lang: string,
+    friendsCount: int,
+    statusesCount: int,
+    name: string,
+    followersCount: int
+};
+
+CREATE TYPE EmploymentType AS {
+    organizationName: string,
+    startDate: date,
+    endDate: date?
+};
+
+CREATE TYPE GleambookUserType AS {
+    id: int,
+    alias: string,
+    name: string,
+    userSince: datetime,
+    friendIds: {{ int }},
+    employment: [EmploymentType]
+};
+
+CREATE DATASET GleambookUsers(GleambookUserType) PRIMARY KEY id;
+CREATE DATASET ChirpUsers(ChirpUserType) PRIMARY KEY screenName;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.2.update.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.2.update.sqlpp
new file mode 100644
index 0000000..efd7565
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.2.update.sqlpp
@@ -0,0 +1,42 @@
+/*
+ * 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 TinySocial;
+
+INSERT INTO ChirpUsers
+([
+{"screenName":"NathanGiesen@211","lang":"en","friendsCount":18,"statusesCount":473,"name":"Nathan Giesen","followersCount":49416},
+{"screenName":"ColineGeyer@63","lang":"en","friendsCount":121,"statusesCount":362,"name":"Coline Geyer","followersCount":17159},
+{"screenName":"NilaMilliron_tw","lang":"en","friendsCount":445,"statusesCount":164,"name":"Nila Milliron","followersCount":22649},
+{"screenName":"ChangEwing_573","lang":"en","friendsCount":182,"statusesCount":394,"name":"Chang Ewing","followersCount":32136}
+]);
+
+INSERT INTO GleambookUsers
+([
+{"id":1,"alias":"Margarita","name":"MargaritaStoddard","nickname":"Mags","userSince":datetime("2012-08-20T10:10:00"),"friendIds":{{2,3,6,10}},"employment":[{"organizationName":"Codetechno","startDate":date("2006-08-06")},{"organizationName":"geomedia","startDate":date("2010-06-17"),"endDate":date("2010-01-26")}],"gender":"F"},
+{"id":2,"alias":"Isbel","name":"IsbelDull","nickname":"Izzy","userSince":datetime("2011-01-22T10:10:00"),"friendIds":{{1,4}},"employment":[{"organizationName":"Hexviafind","startDate":date("2010-04-27")}]},
+{"id":3,"alias":"Emory","name":"EmoryUnk","userSince":datetime("2012-07-10T10:10:00"),"friendIds":{{1,5,8,9}},"employment":[{"organizationName":"geomedia","startDate":date("2010-06-17"),"endDate":date("2010-01-26")}]},
+{"id":4,"alias":"Nicholas","name":"NicholasStroh","userSince":datetime("2010-12-27T10:10:00"),"friendIds":{{2}},"employment":[{"organizationName":"Zamcorporation","startDate":date("2010-06-08")}]},
+{"id":5,"alias":"Von","name":"VonKemble","userSince":datetime("2010-01-05T10:10:00"),"friendIds":{{3,6,10}},"employment":[{"organizationName":"Kongreen","startDate":date("2010-11-27")}]},
+{"id":6,"alias":"Willis","name":"WillisWynne","userSince":datetime("2005-01-17T10:10:00"),"friendIds":{{1,3,7}},"employment":[{"organizationName":"jaydax","startDate":date("2009-05-15")}]},
+{"id":7,"alias":"Suzanna","name":"SuzannaTillson","userSince":datetime("2012-08-07T10:10:00"),"friendIds":{{6}},"employment":[{"organizationName":"Labzatron","startDate":date("2011-04-19")}]},
+{"id":8,"alias":"Nila","name":"NilaMilliron","userSince":datetime("2008-01-01T10:10:00"),"friendIds":{{3}},"employment":[{"organizationName":"Plexlane","startDate":date("2010-02-28")}]},
+{"id":9,"alias":"Woodrow","name":"WoodrowNehling","nickname":"Woody","userSince":datetime("2005-09-20T10:10:00"),"friendIds":{{3,10}},"employment":[{"organizationName":"Zuncan","startDate":date("2003-04-22"),"endDate":date("2009-12-13")}]},
+{"id":10,"alias":"Bram","name":"BramHatch","userSince":datetime("2010-10-16T10:10:00"),"friendIds":{{1,5,9}},"employment":[{"organizationName":"physcane","startDate":date("2007-06-05"),"endDate":date("2011-11-05")}]}
+]);
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.3.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.3.query.sqlpp
new file mode 100644
index 0000000..2e6c3a5
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.3.query.sqlpp
@@ -0,0 +1,24 @@
+/*
+ * 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.
+ */
+
+// testing fix for ASTERIXDB-2288 related to field access with UNION
+USE TinySocial;
+
+SELECT VALUE a FROM (SELECT VALUE c FROM ChirpUsers c UNION ALL SELECT VALUE g FROM GleambookUsers g) AS a
+ORDER BY a.name;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.4.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.4.query.sqlpp
new file mode 100644
index 0000000..c222d57
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.4.query.sqlpp
@@ -0,0 +1,24 @@
+/*
+ * 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.
+ */
+
+// testing fix for ASTERIXDB-2288 related to field access with UNION
+USE TinySocial;
+
+SELECT name FROM (SELECT VALUE c FROM ChirpUsers c UNION ALL SELECT VALUE g FROM GleambookUsers g) AS a
+ORDER BY name;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.5.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.5.query.sqlpp
new file mode 100644
index 0000000..922012b
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.5.query.sqlpp
@@ -0,0 +1,25 @@
+/*
+ * 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.
+ */
+
+// testing fix for ASTERIXDB-2288 related to field access with UNION
+USE TinySocial;
+
+SELECT name, string_length(name) as len
+FROM (SELECT VALUE c FROM ChirpUsers c UNION ALL SELECT VALUE g FROM GleambookUsers g) AS a
+ORDER BY name;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.6.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.6.query.sqlpp
new file mode 100644
index 0000000..8447214
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.6.query.sqlpp
@@ -0,0 +1,24 @@
+/*
+ * 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.
+ */
+
+// testing fix for ASTERIXDB-2288 related to field access with UNION
+USE TinySocial;
+
+SELECT alias FROM (SELECT VALUE c FROM ChirpUsers c UNION ALL SELECT VALUE g FROM GleambookUsers g) AS a
+ORDER BY alias;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.7.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.7.ddl.sqlpp
new file mode 100644
index 0000000..97845a0
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.7.ddl.sqlpp
@@ -0,0 +1,20 @@
+/*
+ * 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 TinySocial IF EXISTS;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.3.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.3.adm
new file mode 100644
index 0000000..bfbb1bd
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.3.adm
@@ -0,0 +1,14 @@
+{ "name": "BramHatch", "id": 10, "alias": "Bram", "userSince": datetime("2010-10-16T10:10:00.000Z"), "friendIds": {{ 1, 5, 9 }}, "employment": [ { "organizationName": "physcane", "startDate": date("2007-06-05"), "endDate": date("2011-11-05") } ] }
+{ "name": "Chang Ewing", "screenName": "ChangEwing_573", "lang": "en", "friendsCount": 182, "statusesCount": 394, "followersCount": 32136 }
+{ "name": "Coline Geyer", "screenName": "ColineGeyer@63", "lang": "en", "friendsCount": 121, "statusesCount": 362, "followersCount": 17159 }
+{ "name": "EmoryUnk", "id": 3, "alias": "Emory", "userSince": datetime("2012-07-10T10:10:00.000Z"), "friendIds": {{ 1, 5, 8, 9 }}, "employment": [ { "organizationName": "geomedia", "startDate": date("2010-06-17"), "endDate": date("2010-01-26") } ] }
+{ "name": "IsbelDull", "id": 2, "alias": "Isbel", "userSince": datetime("2011-01-22T10:10:00.000Z"), "friendIds": {{ 1, 4 }}, "employment": [ { "organizationName": "Hexviafind", "startDate": date("2010-04-27") } ], "nickname": "Izzy" }
+{ "name": "MargaritaStoddard", "id": 1, "alias": "Margarita", "userSince": datetime("2012-08-20T10:10:00.000Z"), "friendIds": {{ 2, 3, 6, 10 }}, "employment": [ { "organizationName": "Codetechno", "startDate": date("2006-08-06") }, { "organizationName": "geomedia", "startDate": date("2010-06-17"), "endDate": date("2010-01-26") } ], "nickname": "Mags", "gender": "F" }
+{ "name": "Nathan Giesen", "screenName": "NathanGiesen@211", "lang": "en", "friendsCount": 18, "statusesCount": 473, "followersCount": 49416 }
+{ "name": "NicholasStroh", "id": 4, "alias": "Nicholas", "userSince": datetime("2010-12-27T10:10:00.000Z"), "friendIds": {{ 2 }}, "employment": [ { "organizationName": "Zamcorporation", "startDate": date("2010-06-08") } ] }
+{ "name": "Nila Milliron", "screenName": "NilaMilliron_tw", "lang": "en", "friendsCount": 445, "statusesCount": 164, "followersCount": 22649 }
+{ "name": "NilaMilliron", "id": 8, "alias": "Nila", "userSince": datetime("2008-01-01T10:10:00.000Z"), "friendIds": {{ 3 }}, "employment": [ { "organizationName": "Plexlane", "startDate": date("2010-02-28") } ] }
+{ "name": "SuzannaTillson", "id": 7, "alias": "Suzanna", "userSince": datetime("2012-08-07T10:10:00.000Z"), "friendIds": {{ 6 }}, "employment": [ { "organizationName": "Labzatron", "startDate": date("2011-04-19") } ] }
+{ "name": "VonKemble", "id": 5, "alias": "Von", "userSince": datetime("2010-01-05T10:10:00.000Z"), "friendIds": {{ 3, 6, 10 }}, "employment": [ { "organizationName": "Kongreen", "startDate": date("2010-11-27") } ] }
+{ "name": "WillisWynne", "id": 6, "alias": "Willis", "userSince": datetime("2005-01-17T10:10:00.000Z"), "friendIds": {{ 1, 3, 7 }}, "employment": [ { "organizationName": "jaydax", "startDate": date("2009-05-15") } ] }
+{ "name": "WoodrowNehling", "id": 9, "alias": "Woodrow", "userSince": datetime("2005-09-20T10:10:00.000Z"), "friendIds": {{ 3, 10 }}, "employment": [ { "organizationName": "Zuncan", "startDate": date("2003-04-22"), "endDate": date("2009-12-13") } ], "nickname": "Woody" }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.4.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.4.adm
new file mode 100644
index 0000000..8660d985
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.4.adm
@@ -0,0 +1,14 @@
+{ "name": "BramHatch" }
+{ "name": "Chang Ewing" }
+{ "name": "Coline Geyer" }
+{ "name": "EmoryUnk" }
+{ "name": "IsbelDull" }
+{ "name": "MargaritaStoddard" }
+{ "name": "Nathan Giesen" }
+{ "name": "NicholasStroh" }
+{ "name": "Nila Milliron" }
+{ "name": "NilaMilliron" }
+{ "name": "SuzannaTillson" }
+{ "name": "VonKemble" }
+{ "name": "WillisWynne" }
+{ "name": "WoodrowNehling" }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.5.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.5.adm
new file mode 100644
index 0000000..4af8057
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.5.adm
@@ -0,0 +1,14 @@
+{ "name": "BramHatch", "len": 9 }
+{ "name": "Chang Ewing", "len": 11 }
+{ "name": "Coline Geyer", "len": 12 }
+{ "name": "EmoryUnk", "len": 8 }
+{ "name": "IsbelDull", "len": 9 }
+{ "name": "MargaritaStoddard", "len": 17 }
+{ "name": "Nathan Giesen", "len": 13 }
+{ "name": "NicholasStroh", "len": 13 }
+{ "name": "Nila Milliron", "len": 13 }
+{ "name": "NilaMilliron", "len": 12 }
+{ "name": "SuzannaTillson", "len": 14 }
+{ "name": "VonKemble", "len": 9 }
+{ "name": "WillisWynne", "len": 11 }
+{ "name": "WoodrowNehling", "len": 14 }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.6.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.6.adm
new file mode 100644
index 0000000..ea37f8c
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/misc/field_access_union-ASTERIXDB-2288/field_access_union-ASTERIXDB-2288.6.adm
@@ -0,0 +1,14 @@
+{  }
+{  }
+{  }
+{  }
+{ "alias": "Bram" }
+{ "alias": "Emory" }
+{ "alias": "Isbel" }
+{ "alias": "Margarita" }
+{ "alias": "Nicholas" }
+{ "alias": "Nila" }
+{ "alias": "Suzanna" }
+{ "alias": "Von" }
+{ "alias": "Willis" }
+{ "alias": "Woodrow" }
\ 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 9055c85..3ea99ee 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_sqlpp.xml
@@ -5640,6 +5640,11 @@
       </compilation-unit>
     </test-case>
     <test-case FilePath="misc">
+      <compilation-unit name="field_access_union-ASTERIXDB-2288">
+        <output-dir compare="Text">field_access_union-ASTERIXDB-2288</output-dir>
+      </compilation-unit>
+    </test-case>
+    <test-case FilePath="misc">
       <compilation-unit name="constant_folding">
         <output-dir compare="Text">constant_folding</output-dir>
       </compilation-unit>
diff --git a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignBelowUnionAllRule.java b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignBelowUnionAllRule.java
index f432c9f..145761c 100644
--- a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignBelowUnionAllRule.java
+++ b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/PushAssignBelowUnionAllRule.java
@@ -79,7 +79,7 @@
         }
 
         boolean modified = false;
-        for (int i = 0; i < op.getInputs().size(); i++) {
+        inputs_loop: for (int i = 0; i < op.getInputs().size(); i++) {
             AbstractLogicalOperator childOp = (AbstractLogicalOperator) op.getInputs().get(i).getValue();
             if (childOp.getOperatorTag() != LogicalOperatorTag.ASSIGN) {
                 continue;
@@ -87,7 +87,7 @@
             AssignOperator assignOp = (AssignOperator) childOp;
             for (Mutable<ILogicalExpression> expr : assignOp.getExpressions()) {
                 if (!expr.getValue().isFunctional()) {
-                    return false;
+                    continue inputs_loop;
                 }
             }
 
@@ -96,26 +96,23 @@
                 continue;
             }
             UnionAllOperator unionOp = (UnionAllOperator) childOfChildOp;
-
-            Set<LogicalVariable> assignUsedVars = new HashSet<LogicalVariable>();
+            Set<LogicalVariable> assignUsedVars = new HashSet<>();
             VariableUtilities.getUsedVariables(assignOp, assignUsedVars);
-
             List<LogicalVariable> assignVars = assignOp.getVariables();
-
             AssignOperator[] newAssignOps = new AssignOperator[2];
             for (int j = 0; j < unionOp.getInputs().size(); j++) {
                 newAssignOps[j] = createAssignBelowUnionAllBranch(unionOp, j, assignOp, assignUsedVars, context);
+                if (newAssignOps[j] == null) {
+                    continue inputs_loop;
+                }
             }
             // Add original assign variables to the union variable mappings.
             for (int j = 0; j < assignVars.size(); j++) {
                 LogicalVariable first = newAssignOps[0].getVariables().get(j);
                 LogicalVariable second = newAssignOps[1].getVariables().get(j);
-                Triple<LogicalVariable, LogicalVariable, LogicalVariable> varMapping =
-                        new Triple<LogicalVariable, LogicalVariable, LogicalVariable>(first, second, assignVars.get(j));
-                unionOp.getVariableMappings().add(varMapping);
+                unionOp.getVariableMappings().add(new Triple<>(first, second, assignVars.get(j)));
             }
             context.computeAndSetTypeEnvironmentForOperator(unionOp);
-
             // Remove original assign operator.
             op.getInputs().set(i, assignOp.getInputs().get(0));
             context.computeAndSetTypeEnvironmentForOperator(op);
@@ -128,9 +125,11 @@
     private AssignOperator createAssignBelowUnionAllBranch(UnionAllOperator unionOp, int inputIndex,
             AssignOperator originalAssignOp, Set<LogicalVariable> assignUsedVars, IOptimizationContext context)
             throws AlgebricksException {
-        AssignOperator newAssignOp = cloneAssignOperator(originalAssignOp, context);
-        newAssignOp.getInputs()
-                .add(new MutableObject<ILogicalOperator>(unionOp.getInputs().get(inputIndex).getValue()));
+        AssignOperator newAssignOp = cloneAssignOperator(originalAssignOp, context, unionOp, inputIndex);
+        if (newAssignOp == null) {
+            return null;
+        }
+        newAssignOp.getInputs().add(new MutableObject<>(unionOp.getInputs().get(inputIndex).getValue()));
         unionOp.getInputs().get(inputIndex).setValue(newAssignOp);
         int numVarMappings = unionOp.getVariableMappings().size();
         for (int i = 0; i < numVarMappings; i++) {
@@ -151,20 +150,31 @@
 
     /**
      * Clones the given assign operator changing the returned variables to be new ones.
-     * Also, leaves the inputs of the clone clear.
+     * Also, leaves the inputs of the clone clear. It returns null if the assign operator cannot be pushed.
      */
-    private AssignOperator cloneAssignOperator(AssignOperator assignOp, IOptimizationContext context) {
-        List<LogicalVariable> vars = new ArrayList<LogicalVariable>();
-        List<Mutable<ILogicalExpression>> exprs = new ArrayList<Mutable<ILogicalExpression>>();
+    private AssignOperator cloneAssignOperator(AssignOperator assignOp, IOptimizationContext context,
+            UnionAllOperator unionOp, int inputIndex) throws AlgebricksException {
+        List<LogicalVariable> vars = new ArrayList<>();
+        List<Mutable<ILogicalExpression>> exprs = new ArrayList<>();
         int numVars = assignOp.getVariables().size();
         for (int i = 0; i < numVars; i++) {
             vars.add(context.newVar());
-            exprs.add(new MutableObject<ILogicalExpression>(
-                    assignOp.getExpressions().get(i).getValue().cloneExpression()));
+            ILogicalExpression clonedExpression = assignOp.getExpressions().get(i).getValue().cloneExpression();
+            if (!modifyExpression(clonedExpression, unionOp, context, inputIndex)) {
+                return null; // bail if the expression couldn't be modified according to the branch it is moved to
+            }
+            exprs.add(new MutableObject<>(clonedExpression));
         }
         AssignOperator assignCloneOp = new AssignOperator(vars, exprs);
         assignCloneOp.setSourceLocation(assignOp.getSourceLocation());
         assignCloneOp.setExecutionMode(assignOp.getExecutionMode());
         return assignCloneOp;
     }
+
+    // modifies the cloned expression according to the branch it'll be moved to. returns true if successful.
+    protected boolean modifyExpression(ILogicalExpression expression, UnionAllOperator unionOp,
+            IOptimizationContext ctx, int inputIndex) throws AlgebricksException {
+        // default implementation does not check specific expressions
+        return true;
+    }
 }