server: support default TTL for a table (#206)

src/base/pegasus_value_schema.h

@@ -56,6 +56,21 @@ pegasus_extract_user_data(uint32_t version, std::string &&raw_value, ::dsn::blob
     user_data.assign(std::move(buf), 0, static_cast<unsigned int>(view.length()));
 }
 
+/// Update expire_ts in rocksdb value with given version.
+/// The value schema must be in v0.
+inline void pegasus_update_expire_ts(uint32_t version, std::string &value, uint32_t new_expire_ts)
+{
+    if (version == 0) {
+        dassert_f(value.length() >= sizeof(uint32_t), "value must include 'expire_ts' header");
+
+        new_expire_ts = dsn::endian::hton(new_expire_ts);
+        memcpy(const_cast<char *>(value.data()), &new_expire_ts, sizeof(uint32_t));
+    } else {
+        dfatal_f("unsupported value schema version: {}", version);
+        __builtin_unreachable();
+    }
+}
+
 /// \return true if expired
 inline bool check_if_ts_expired(uint32_t epoch_now, uint32_t expire_ts)
 {

src/server/key_ttl_compaction_filter.h

@@ -37,16 +37,8 @@ public:
             pegasus_extract_expire_ts(_value_schema_version, utils::to_string_view(existing_value));
         if (_default_ttl != 0 && expire_ts == 0) {
             // should update ttl
-            dsn::blob user_data;
-            pegasus_extract_user_data(_value_schema_version,
-                                      std::string(existing_value.data(), existing_value.length()),
-                                      user_data);
-            rocksdb::SliceParts sparts = _gen.generate_value(_value_schema_version,
-                                                             dsn::string_view(user_data),
-                                                             utils::epoch_now() + _default_ttl);
-            for (int i = 0; i < sparts.num_parts; i++) {
-                *new_value += sparts.parts[i].ToString();
-            }
+            *new_value = existing_value.ToString();
+            pegasus_update_expire_ts(_value_schema_version, *new_value, utils::epoch_now() + _default_ttl);
             *value_changed = true;
             return false;
         }