Support Segment for BetaRowset (#1577)

We create a new segment format for BetaRowset. New format merge
data file and index file into one file. And we create a new format
for short key index. In origin code index is stored in format like
RowCusor which is not efficient to compare. Now we encode multiple
column into binary, and we assure that this binary is sorted same
with the key columns.

be/src/olap/key_coder.cpp

@@ -0,0 +1,80 @@
+// 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.
+
+#include "olap/key_coder.h"
+
+#include <unordered_map>
+
+namespace doris {
+
+template<typename TraitsType>
+KeyCoder::KeyCoder(TraitsType traits) 
+        : _encode_ascending(traits.encode_ascending),
+        _decode_ascending(traits.decode_ascending) {
+}
+
+// Helper class used to get KeyCoder
+class KeyCoderResolver {
+public:
+    ~KeyCoderResolver() {
+        for (auto& iter : _coder_map) {
+            delete iter.second;
+        }
+    }
+
+    static KeyCoderResolver* instance() {
+        static KeyCoderResolver s_instance;
+        return &s_instance;
+    }
+
+    KeyCoder* get_coder(FieldType field_type) const {
+        auto it = _coder_map.find(field_type);
+        if (it != _coder_map.end()) {
+            return it->second;
+        }
+        return nullptr;
+    }
+
+private:
+    KeyCoderResolver() {
+        add_mapping<OLAP_FIELD_TYPE_TINYINT>();
+        add_mapping<OLAP_FIELD_TYPE_SMALLINT>();
+        add_mapping<OLAP_FIELD_TYPE_INT>();
+        add_mapping<OLAP_FIELD_TYPE_UNSIGNED_INT>();
+        add_mapping<OLAP_FIELD_TYPE_BIGINT>();
+        add_mapping<OLAP_FIELD_TYPE_LARGEINT>();
+        add_mapping<OLAP_FIELD_TYPE_DATETIME>();
+
+        add_mapping<OLAP_FIELD_TYPE_DATE>();
+        add_mapping<OLAP_FIELD_TYPE_DECIMAL>();
+        add_mapping<OLAP_FIELD_TYPE_CHAR>();
+        add_mapping<OLAP_FIELD_TYPE_VARCHAR>();
+    }
+
+    template<FieldType field_type>
+    void add_mapping() {
+        _coder_map.emplace(field_type, new KeyCoder(KeyCoderTraits<field_type>()));
+    }
+
+    std::unordered_map<FieldType, KeyCoder*> _coder_map;
+};
+
+const KeyCoder* get_key_coder(FieldType type) {
+    return KeyCoderResolver::instance()->get_coder(type);
+}
+
+}