[GitHub] [incubator-kvrocks] PragmaTwice commented on a diff in pull request #1367: Use prefix extractor to improve performance

["PragmaTwice (via GitHub)" <gi...@apache.org>]

PragmaTwice commented on code in PR #1367:
URL: https://github.com/apache/incubator-kvrocks/pull/1367#discussion_r1158013656


##########
src/storage/prefix_extractor.h:
##########
@@ -0,0 +1,67 @@
+/*
+ * 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.
+ *
+ */
+
+#pragma once
+
+#include <rocksdb/slice_transform.h>
+
+#include "common/encoding.h"
+
+class SubkeyPrefixExtractor : public rocksdb::SliceTransform {
+ private:
+  bool cluster_enabled_;
+
+ public:
+  explicit SubkeyPrefixExtractor(bool cluster_enabled) : cluster_enabled_(cluster_enabled) {}
+
+  const char *Name() const override { return "sub_key_prefix_extractor"; }
+
+  rocksdb::Slice Transform(const rocksdb::Slice &key) const override {
+    const char *ptr = key.data();
+    uint8_t ns_size = ptr[0];
+    ptr += 1 + ns_size;  // drop ns encoding size and ns
+    if (cluster_enabled_) {
+      // add the cluster slot size if it's enabled
+      ptr += 2;
+    }
+
+    // return the origin key if it's too short
+    if (ptr > key.data() + key.size()) return key;
+    uint32_t key_size = DecodeFixed32(ptr);
+
+    ptr += 4 + key_size;  // drop key encoding size and key
+    // return the origin key if it's too short
+    if (ptr > key.data() + key.size()) return key;
+
+    size_t prefix_len = 1 /* ns encoding size */ + ns_size + 4 /* encoding key size */ + key_size;
+    if (cluster_enabled_) {
+      prefix_len += 2;  // add slot id encoding size if the cluster mode is enabled
+    }
+    return {key.data(), prefix_len};

Review Comment:
   ```suggestion
       return {key.data(), ptr - key.data()};
   ```



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: issues-unsubscribe@kvrocks.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org