Support DISTINCT feature in SELECT clause

src/main/java/com/amazon/opendistroforelasticsearch/sql/domain/Field.java

@@ -16,6 +16,7 @@
 package com.amazon.opendistroforelasticsearch.sql.domain;
 
 import com.alibaba.druid.sql.ast.SQLExpr;
+import com.alibaba.druid.sql.ast.expr.SQLAggregateOption;
 import com.amazon.opendistroforelasticsearch.sql.parser.ChildrenType;
 import com.amazon.opendistroforelasticsearch.sql.parser.NestedType;
 
@@ -38,12 +39,14 @@ public class Field implements Cloneable {
     private NestedType nested;
     private ChildrenType children;
     private SQLExpr expression;
+    private SQLAggregateOption option;
 
     public Field(String name, String alias) {
         this.name = name;
         this.alias = alias;
         this.nested = null;
         this.children = null;
+        this.option = null;
     }
 
     public Field(String name, String alias, NestedType nested, ChildrenType children) {
@@ -104,6 +107,14 @@ public String getChildType() {
         return this.children.childType;
     }
 
+    public void setAggregationOption(SQLAggregateOption option) {
+        this.option = option;
+    }
+
+    public SQLAggregateOption getOption() {
+        return option;
+    }
+
     @Override
     public String toString() {
         return this.name;

src/main/java/com/amazon/opendistroforelasticsearch/sql/domain/MethodField.java

@@ -68,14 +68,6 @@ public String toString() {
         return this.name + "(" + Util.joiner(params, ",") + ")";
     }
 
-    public String getOption() {
-        return option;
-    }
-
-    public void setOption(String option) {
-        this.option = option;
-    }
-
     @Override
     public boolean isNested() {
         Map<String, Object> paramsAsMap = this.getParamsAsMap();

src/main/java/com/amazon/opendistroforelasticsearch/sql/parser/FieldMaker.java

@@ -17,6 +17,7 @@
 
 import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLObject;
+import com.alibaba.druid.sql.ast.SQLSetQuantifier;
 import com.alibaba.druid.sql.ast.expr.SQLAggregateExpr;
 import com.alibaba.druid.sql.ast.expr.SQLAggregateOption;
 import com.alibaba.druid.sql.ast.expr.SQLAllColumnExpr;
@@ -30,6 +31,9 @@
 import com.alibaba.druid.sql.ast.expr.SQLPropertyExpr;
 import com.alibaba.druid.sql.ast.expr.SQLQueryExpr;
 import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
+import com.alibaba.druid.sql.ast.statement.SQLSelectGroupByClause;
+import com.alibaba.druid.sql.ast.statement.SQLSelectItem;
+import com.alibaba.druid.sql.ast.statement.SQLSelectQueryBlock;
 import com.amazon.opendistroforelasticsearch.sql.domain.Field;
 import com.amazon.opendistroforelasticsearch.sql.domain.KVValue;
 import com.amazon.opendistroforelasticsearch.sql.domain.MethodField;
@@ -57,6 +61,28 @@ public class FieldMaker {
     public Field makeField(SQLExpr expr, String alias, String tableAlias) throws SqlParseException {
         Field field = makeFieldImpl(expr, alias, tableAlias);
 
+        /**
+         * If a token of DISTINCT is in the SELECT clause, it will parsed and stored into the SQLSelectQueryBlock
+         * as a property of "DistionOpion"
+         * The following code block would be working only in the case of
+         * SELECT DISTINCT + fieldname (aka. SELECT DISTINCT(fieldname))
+         */
+        if (expr.getParent() != null && expr.getParent() instanceof SQLSelectItem
+                && expr.getParent().getParent() != null
+                && expr.getParent().getParent() instanceof SQLSelectQueryBlock) {
+            SQLSelectQueryBlock queryBlock = (SQLSelectQueryBlock) expr.getParent().getParent();
+            if (queryBlock.getDistionOption() == SQLSetQuantifier.DISTINCT) {
+                SQLAggregateOption option = SQLAggregateOption.DISTINCT;
+                field.setAggregationOption(option);
+                if (queryBlock.getGroupBy() == null) {
+                    queryBlock.setGroupBy(new SQLSelectGroupByClause());
+                }
+                SQLSelectGroupByClause groupByClause = queryBlock.getGroupBy();
+                groupByClause.addItem(expr);
+                queryBlock.setGroupBy(groupByClause);
+            }
+        }
+
         // why we may get null as a field???
         if (field != null) {
             field.setExpression(expr);
@@ -73,7 +99,6 @@ private Field makeFieldImpl(SQLExpr expr, String alias, String tableAlias) throw
         } else if (expr instanceof SQLBinaryOpExpr) {
             //make a SCRIPT method field;
             return makeFieldImpl(makeBinaryMethodField((SQLBinaryOpExpr) expr, alias, true), alias, tableAlias);
-
         } else if (expr instanceof SQLAllColumnExpr) {
             return Field.STAR;
         } else if (expr instanceof SQLMethodInvokeExpr) {

src/test/java/com/amazon/opendistroforelasticsearch/sql/esintgtest/AggregationIT.java

@@ -1184,6 +1184,23 @@ public void groupByScriptedHistogram() throws Exception {
         Assert.assertThat(result, containsString("\"script\":{\"source\""));
     }
 
+    @Test
+    public void distinctWithOneField() {
+        Assert.assertEquals(
+                executeQuery("SELECT DISTINCT name.lastname FROM " + TEST_INDEX_GAME_OF_THRONES, "jdbc"),
+                executeQuery("SELECT name.lastname FROM " + TEST_INDEX_GAME_OF_THRONES
+                        + " GROUP BY name.lastname", "jdbc")
+        );
+    }
+
+    @Test
+    public void distinctWithMultipleFields() {
+        Assert.assertEquals(
+                executeQuery("SELECT DISTINCT age, gender FROM " + TEST_INDEX_ACCOUNT, "jdbc"),
+                executeQuery("SELECT age, gender FROM " + TEST_INDEX_ACCOUNT
+                        + " GROUP BY age, gender", "jdbc")
+        );
+    }
 
     private JSONObject getAggregation(final JSONObject queryResult, final String aggregationName)
     {

src/test/java/com/amazon/opendistroforelasticsearch/sql/unittest/AggregationOptionTest.java

@@ -0,0 +1,43 @@
+/*
+ *   Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *   Licensed under the Apache License, Version 2.0 (the "License").
+ *   You may not use this file except in compliance with the License.
+ *   A copy of the License is located at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   or in the "license" file accompanying this file. This file 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 com.amazon.opendistroforelasticsearch.sql.unittest;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import static com.amazon.opendistroforelasticsearch.sql.util.SqlExplainUtils.explain;
+
+/**
+ * Unit test class for feature of aggregation options: DISTINCT, ALL, UNIQUE, DEDUPLICATION
+ */
+public class AggregationOptionTest {
+
+    @Test
+    public void distinctWithOneField() {
+        Assert.assertEquals(
+                explain("SELECT DISTINCT lastname FROM accounts"),
+                explain("SELECT lastname FROM accounts GROUP BY lastname")
+        );
+    }
+
+    @Test
+    public void distinctWithMultipleFields() {
+        Assert.assertEquals(
+                explain("SELECT DISTINCT city, age, balance FROM accounts"),
+                explain("SELECT city, age, balance FROM accounts GROUP BY city, age, balance")
+        );
+    }
+}

src/test/java/com/amazon/opendistroforelasticsearch/sql/unittest/QueryFunctionsTest.java

@@ -15,11 +15,9 @@
 
 package com.amazon.opendistroforelasticsearch.sql.unittest;
 
-import com.alibaba.druid.sql.parser.ParserException;
 import com.amazon.opendistroforelasticsearch.sql.esintgtest.TestsConstants;
 import com.amazon.opendistroforelasticsearch.sql.exception.SqlParseException;
 import com.amazon.opendistroforelasticsearch.sql.query.ESActionFactory;
-import com.amazon.opendistroforelasticsearch.sql.query.QueryAction;
 import com.amazon.opendistroforelasticsearch.sql.util.CheckScriptContents;
 import org.apache.lucene.search.join.ScoreMode;
 import org.elasticsearch.client.Client;
@@ -33,6 +31,7 @@
 
 import java.sql.SQLFeatureNotSupportedException;
 
+import static com.amazon.opendistroforelasticsearch.sql.util.SqlExplainUtils.explain;
 import static org.elasticsearch.index.query.QueryBuilders.constantScoreQuery;
 import static org.elasticsearch.index.query.QueryBuilders.matchPhraseQuery;
 import static org.elasticsearch.index.query.QueryBuilders.matchQuery;
@@ -306,18 +305,6 @@ private String query(String sql) {
         return explain(sql);
     }
 
-    private String explain(String sql) {
-        try {
-            Client mockClient = Mockito.mock(Client.class);
-            CheckScriptContents.stubMockClient(mockClient);
-            QueryAction queryAction = ESActionFactory.create(mockClient, sql);
-
-            return queryAction.explain().explain();
-        } catch (SqlParseException | SQLFeatureNotSupportedException e) {
-            throw new ParserException("Illegal sql expr in: " + sql);
-        }
-    }
-
     private Matcher<String> contains(AbstractQueryBuilder queryBuilder) {
         return containsString(Strings.toString(queryBuilder, false, false));
     }

src/test/java/com/amazon/opendistroforelasticsearch/sql/util/SqlExplainUtils.java

@@ -0,0 +1,45 @@
+/*
+ *   Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *   Licensed under the Apache License, Version 2.0 (the "License").
+ *   You may not use this file except in compliance with the License.
+ *   A copy of the License is located at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   or in the "license" file accompanying this file. This file 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 com.amazon.opendistroforelasticsearch.sql.util;
+
+import com.alibaba.druid.sql.parser.ParserException;
+import com.amazon.opendistroforelasticsearch.sql.exception.SqlParseException;
+import com.amazon.opendistroforelasticsearch.sql.query.ESActionFactory;
+import com.amazon.opendistroforelasticsearch.sql.query.QueryAction;
+import org.elasticsearch.client.Client;
+import org.mockito.Mockito;
+
+import java.sql.SQLFeatureNotSupportedException;
+
+/**
+ * Test utils class that explains a query
+ */
+public class SqlExplainUtils {
+
+    public static String explain(String query) {
+        try {
+            Client mockClient = Mockito.mock(Client.class);
+            CheckScriptContents.stubMockClient(mockClient);
+            QueryAction queryAction = ESActionFactory.create(mockClient, query);
+
+            return queryAction.explain().explain();
+        } catch (SqlParseException | SQLFeatureNotSupportedException e) {
+            throw new ParserException("Illegal sql expr in: " + query);
+        }
+    }
+
+    private SqlExplainUtils() {}
+}