Extreme trimming on startup

Author: psgreco

src/txdb.cpp

@@ -308,41 +308,6 @@ bool CBlockTreeDB::WritePAKList(const std::vector<std::vector<unsigned char> >&
         return Write(std::make_pair(DB_PAK, uint256S("1")), offline_list) && Write(std::make_pair(DB_PAK, uint256S("2")), online_list) && Write(std::make_pair(DB_PAK, uint256S("3")), reject);
 }
 
-/** Note that we only get a conservative (lower) estimate of the max header height here,
- * obtained by sampling the first 10,000 headers on disk (which are in random order) and
- * taking the highest block we see. */
-bool CBlockTreeDB::WalkBlockIndexGutsForMaxHeight(int* nHeight) {
-    std::unique_ptr<CDBIterator> pcursor(NewIterator());
-    *nHeight = 0;
-    int i = 0;
-    pcursor->Seek(std::make_pair(DB_BLOCK_INDEX, uint256()));
-    while (pcursor->Valid()) {
-        if (ShutdownRequested()) return false;
-        std::pair<uint8_t, uint256> key;
-        if (pcursor->GetKey(key) && key.first == DB_BLOCK_INDEX) {
-            i++;
-            if (i > 10'000) {
-                // Under the (accurate) assumption that the headers on disk are effectively in random height order,
-                //   we have a good-enough (conservative) estimate of the max height very quickly, and don't need to
-                //   waste more time. Shortcutting like this will cause us to keep a few extra headers, which is fine.
-                break;
-            }
-            CDiskBlockIndex diskindex;
-            if (pcursor->GetValue(diskindex)) {
-                if (diskindex.nHeight > *nHeight) {
-                    *nHeight = diskindex.nHeight;
-                }
-                pcursor->Next();
-            } else {
-                return error("%s: failed to read value", __func__);
-            }
-        } else {
-            break;
-        }
-    }
-    return true;
-}
-
 const CBlockIndex *CBlockTreeDB::RegenerateFullIndex(const CBlockIndex *pindexTrimmed, CBlockIndex *pindexNew) const
 {
     if(!pindexTrimmed->trimmed()) {

src/txdb.h

@@ -88,7 +88,6 @@ class CBlockTreeDB : public CDBWrapper
     bool LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex, int trimBelowHeight);
     // ELEMENTS:
     const CBlockIndex* RegenerateFullIndex(const CBlockIndex *pindexTrimmed, CBlockIndex *pindexNew) const;
-    bool WalkBlockIndexGutsForMaxHeight(int* nHeight);
     bool ReadPAKList(std::vector<std::vector<unsigned char> >& offline_list, std::vector<std::vector<unsigned char> >& online_list, bool& reject);
     bool WritePAKList(const std::vector<std::vector<unsigned char> >& offline_list, const std::vector<std::vector<unsigned char> >& online_list, bool reject);
 };

src/validation.cpp

@@ -4161,15 +4161,7 @@ bool BlockManager::LoadBlockIndex(
 {
     int trim_below_height = 0;
     if (fTrimHeaders) {
-        int max_height = 0;
-        if (!blocktree.WalkBlockIndexGutsForMaxHeight(&max_height)) {
-            LogPrintf("LoadBlockIndex: Failed to WalkBlockIndexGutsForMaxHeight.\n");
-            return false;
-        }
-
-        int must_keep_headers = (consensus_params.total_valid_epochs + 2) * consensus_params.dynamic_epoch_length;
-        int extra_headers_buffer = consensus_params.dynamic_epoch_length * 2; // XXX arbitrary
-        trim_below_height = max_height - must_keep_headers - extra_headers_buffer;
+        trim_below_height = std::numeric_limits<int>::max();
     }
     if (!blocktree.LoadBlockIndexGuts(consensus_params, [this](const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) { return this->InsertBlockIndex(hash); }, trim_below_height))
         return false;
@@ -4218,6 +4210,9 @@ bool BlockManager::LoadBlockIndex(
             pindexBestHeader = pindex;
     }
 
+    if (pindexBestHeader) {
+        ForceUntrimHeader(pindexBestHeader);
+    }
     return true;
 }