core: Add defrag support for json objects

Signed-off-by: Abhijat Malviya <[email protected]>

Author: abhijat

src/core/compact_object.cc

@@ -1094,6 +1094,8 @@ bool CompactObj::DefragIfNeeded(PageUsage* page_usage) {
       return false;
     case SMALL_TAG:
       return u_.small_str.DefragIfNeeded(page_usage);
+    case JSON_TAG:
+      return u_.json_obj.DefragIfNeeded(page_usage);
     case INT_TAG:
       page_usage->RecordNotRequired();
       // this is not relevant in this case
@@ -1585,6 +1587,35 @@ MemoryResource* CompactObj::memory_resource() {
   return tl.local_mr;
 }
 
+bool CompactObj::JsonConsT::DefragIfNeeded(PageUsage* page_usage) {
+  if (JsonType* old = json_ptr; page_usage->IsPageForObjectUnderUtilized(old)) {
+    json_ptr = AllocateMR<JsonType>(std::move(*old));
+    DeleteMR<JsonType>(old);
+    return true;
+  }
+  return false;
+}
+
+bool CompactObj::FlatJsonT::DefragIfNeeded(PageUsage* page_usage) {
+  if (uint8_t* old = flat_ptr; page_usage->IsPageForObjectUnderUtilized(old)) {
+    const uint32_t size = json_len;
+    flat_ptr = static_cast<uint8_t*>(tl.local_mr->allocate(size, kAlignSize));
+    memcpy(flat_ptr, old, size);
+    tl.local_mr->deallocate(old, size, kAlignSize);
+    return true;
+  }
+
+  return false;
+}
+
+bool CompactObj::JsonWrapper::DefragIfNeeded(PageUsage* page_usage) {
+  if (JsonEnconding() == kEncodingJsonCons) {
+    return cons.DefragIfNeeded(page_usage);
+  }
+
+  return flat.DefragIfNeeded(page_usage);
+}
+
 constexpr std::pair<CompactObjType, std::string_view> kObjTypeToString[8] = {
     {OBJ_STRING, "string"sv},  {OBJ_LIST, "list"sv},    {OBJ_SET, "set"sv},
     {OBJ_ZSET, "zset"sv},      {OBJ_HASH, "hash"sv},    {OBJ_STREAM, "stream"sv},

src/core/compact_object.h

@@ -491,18 +491,24 @@ class CompactObj {
   struct JsonConsT {
     JsonType* json_ptr;
     size_t bytes_used;
+
+    bool DefragIfNeeded(PageUsage* page_usage);
   };
 
   struct FlatJsonT {
     uint32_t json_len;
     uint8_t* flat_ptr;
+
+    bool DefragIfNeeded(PageUsage* page_usage);
   };
 
   struct JsonWrapper {
     union {
       JsonConsT cons;
       FlatJsonT flat;
     };
+
+    bool DefragIfNeeded(PageUsage* page_usage);
   };
 
   // My main data structure. Union of representations.