[JDBC-V2, Client-V2] fixes problem with duplicate column names

client-v2/src/main/java/com/clickhouse/client/api/metadata/TableSchema.java

@@ -32,13 +32,13 @@ public TableSchema(String tableName, String query, String databaseName, Collecti
         this.columns = ImmutableList.copyOf(columns);
         ImmutableMap.Builder<String, Integer> colIndexMapBuilder = ImmutableMap.builder();
         for (int i = 0; i < this.columns.size(); i++) {
-            ClickHouseColumn column= this.columns.get(i);
+            ClickHouseColumn column = this.columns.get(i);
             if (column.hasDefault()) {
                 this.hasDefaults = true;
             }
             colIndexMapBuilder.put(this.columns.get(i).getColumnName(), i);
         }
-        this.colIndex = colIndexMapBuilder.build();
+        this.colIndex = colIndexMapBuilder.buildKeepingLast();
     }
 
     /**

client-v2/src/test/java/com/clickhouse/client/query/QueryTests.java

@@ -2215,4 +2215,32 @@ public void testSettingsNotChanged() throws Exception{
             Assert.assertEquals(response.getFormat(), ClickHouseFormat.JSONEachRow);
         }
     }
+
+    @Test
+    public void testDuplicateColumnNames() throws Exception {
+        {
+            // simple scenario
+            List<GenericRecord> records = client.queryAll("SELECT 'a', 'a'");
+            GenericRecord record = records.get(0);
+            Assert.assertEquals(record.getString("'a'"), "a");
+            Assert.assertEquals(record.getString(1), "a");
+            Assert.assertEquals(record.getString(2), "a");
+        }
+
+        {
+            client.execute("DROP TABLE IF EXISTS test_duplicate_column_names1").get().close();
+            client.execute("DROP TABLE IF EXISTS test_duplicate_column_names2").get().close();
+            client.execute("CREATE TABLE test_duplicate_column_names1 (name String ) ENGINE = MergeTree ORDER BY ()").get().close();
+            client.execute("INSERT INTO test_duplicate_column_names1 VALUES ('some name')").get().close();
+            client.execute("CREATE TABLE test_duplicate_column_names2 (name String ) ENGINE = MergeTree ORDER BY ()").get().close();
+            client.execute("INSERT INTO test_duplicate_column_names2 VALUES ('another name')").get().close();
+
+            List<GenericRecord> records = client.queryAll("SELECT * FROM test_duplicate_column_names1, test_duplicate_column_names2");
+            GenericRecord record = records.get(0);
+            Assert.assertEquals(record.getString("name"), "some name");
+            Assert.assertEquals(record.getString("test_duplicate_column_names2.name"), "another name");
+            Assert.assertEquals(record.getString(1), "some name");
+            Assert.assertEquals(record.getString(2), "another name");
+        }
+    }
 }

jdbc-v2/src/test/java/com/clickhouse/jdbc/StatementTest.java

@@ -15,6 +15,7 @@
 import java.sql.Connection;
 import java.sql.Date;
 import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.time.LocalDate;
@@ -1189,6 +1190,43 @@ public void testSetFetchSize() throws Exception {
         }
     }
 
+    @Test(groups = {"integration"})
+    public void testResponseWithDuplicateColumns() throws Exception {
+        try (Connection conn = getJdbcConnection(); Statement stmt = conn.createStatement()) {
+
+
+            try (ResultSet rs = stmt.executeQuery("SELECT 'a', 'a'")) {
+                ResultSetMetaData metaData = rs.getMetaData();
+                Assert.assertEquals(metaData.getColumnCount(), 2);
+                Assert.assertEquals(metaData.getColumnName(1), "'a'");
+                Assert.assertEquals(metaData.getColumnName(2), "'a'");
+            }
+
+            {
+                stmt.execute("DROP TABLE IF EXISTS test_jdbc_duplicate_column_names1");
+                stmt.execute("DROP TABLE IF EXISTS test_jdbc_duplicate_column_names2");
+                stmt.execute("CREATE TABLE test_jdbc_duplicate_column_names1 (name String ) ENGINE = MergeTree ORDER BY ()");
+                stmt.execute("INSERT INTO test_jdbc_duplicate_column_names1 VALUES ('some name')");
+                stmt.execute("CREATE TABLE test_jdbc_duplicate_column_names2 (name String ) ENGINE = MergeTree ORDER BY ()");
+                stmt.execute("INSERT INTO test_jdbc_duplicate_column_names2 VALUES ('another name')");
+
+                try (ResultSet rs = stmt.executeQuery("SELECT * FROM test_jdbc_duplicate_column_names1, test_jdbc_duplicate_column_names2")) {
+                    ResultSetMetaData metaData = rs.getMetaData();
+                    Assert.assertEquals(metaData.getColumnCount(), 2);
+                    Assert.assertEquals(metaData.getColumnName(1), "name");
+                    Assert.assertEquals(metaData.getColumnName(2), "test_jdbc_duplicate_column_names2.name");
+
+                    rs.next();
+                    Assert.assertEquals(rs.getString("name"), "some name");
+                    Assert.assertEquals(rs.getString("test_jdbc_duplicate_column_names2.name"), "another name");
+                    Assert.assertEquals(rs.getString(1), "some name");
+                    Assert.assertEquals(rs.getString(2), "another name");
+
+                }
+            }
+        }
+    }
+
     private static String getDBName(Statement stmt) throws SQLException {
         try (ResultSet rs = stmt.executeQuery("SELECT database()")) {
             rs.next();