fixes problem with duplicate column names by leaving last one index in the column index lookup by name map

Author: chernser

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_names_1").get().close();
+            client.execute("DROP TABLE IF EXISTS test_duplicate_column_names_2").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");
+        }
+    }
 }