[GitHub] [doris] compiletheworld commented on a diff in pull request #10921: [feature-wip](unique-key-merge-on-write) Add agg cache for delete bitmap DSIP-018

[GitBox <gi...@apache.org>]

compiletheworld commented on code in PR #10921:
URL: https://github.com/apache/doris/pull/10921#discussion_r922931548


##########
be/src/olap/tablet_meta.cpp:
##########
@@ -869,4 +876,55 @@ void DeleteBitmap::merge(const DeleteBitmap& other) {
     }
 }
 
+// FIXME: do we need a mutex here to get rid of duplicated initializations
+//        of cache entries in some cases?
+std::shared_ptr<roaring::Roaring> DeleteBitmap::get_agg(const BitmapKey& bmk) const {
+    std::string key_str = AggCache::new_key(bmk);
+    CacheKey key(key_str);
+    Cache::Handle* handle = _agg_cache->lookup(key);
+
+    AggCache::Value* val = handle == nullptr
+                                   ? nullptr
+                                   : reinterpret_cast<AggCache::Value*>(_agg_cache->value(handle));
+    static auto ts_ms = [] {
+        return std::chrono::duration_cast<std::chrono::milliseconds>(
+                       std::chrono::system_clock::now().time_since_epoch())
+                .count();
+    };
+    // Renew if needed
+    if (val == nullptr || (val->expiration > 0 && val->expiration < ts_ms())) {

Review Comment:
   Yes, good point.
   There is a chance that the expired cache entry can be added back to the cache, however, the precondition is that nothing has changed since it has been added. That is to say, the loop of L907 still needs to be run, which seems almost the same cost?



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