From f2faf8cdd9efd3ff044d3f67d5cae62addfec679 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@symas.com>
Date: Thu, 7 Jan 2016 13:23:12 +0000
Subject: [PATCH] Use MDB_APPEND mode where possible

When keys are contiguous and monotonically increasing, this gets
denser page utilization (doesn't leave padding in page splits).
Can't be used for keys that are inserted in random order (e.g. hashes)
In total this only saves around 1.5% of space compared to original
DB code. The previous patch accounted for 0.8% savings on its own;
the blocks tables just aren't that big.
---
 src/blockchain_db/lmdb/db_lmdb.cpp | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
index 2017ccb4..805b56ef 100644
--- a/src/blockchain_db/lmdb/db_lmdb.cpp
+++ b/src/blockchain_db/lmdb/db_lmdb.cpp
@@ -707,7 +707,7 @@ void BlockchainLMDB::add_output(const crypto::hash& tx_hash, const tx_out& tx_ou
   MDB_val_copy<uint64_t> k(m_num_outputs);
   MDB_val_copy<crypto::hash> v(tx_hash);
 
-  result = mdb_cursor_put(m_cur_output_txs, &k, &v, 0);
+  result = mdb_cursor_put(m_cur_output_txs, &k, &v, MDB_APPEND);
   if (result)
     throw0(DB_ERROR(std::string("Failed to add output tx hash to db transaction: ").append(mdb_strerror(result)).c_str()));
   result = mdb_cursor_put(m_cur_tx_outputs, &v, &k, 0);
@@ -715,7 +715,7 @@ void BlockchainLMDB::add_output(const crypto::hash& tx_hash, const tx_out& tx_ou
     throw0(DB_ERROR(std::string("Failed to add <tx hash, global output index> to db transaction: ").append(mdb_strerror(result)).c_str()));
 
   MDB_val_copy<uint64_t> val_local_index(local_index);
-  result = mdb_cursor_put(m_cur_output_indices, &k, &val_local_index, 0);
+  result = mdb_cursor_put(m_cur_output_indices, &k, &val_local_index, MDB_APPEND);
   if (result)
     throw0(DB_ERROR(std::string("Failed to add tx output index to db transaction: ").append(mdb_strerror(result)).c_str()));
 
@@ -733,7 +733,7 @@ void BlockchainLMDB::add_output(const crypto::hash& tx_hash, const tx_out& tx_ou
 
     MDB_val_copy<output_data_t> data(od);
     //MDB_val_copy<crypto::public_key> val_pubkey(boost::get<txout_to_key>(tx_output.target).key);
-    if (mdb_cursor_put(m_cur_output_keys, &k, &data, 0))
+    if (mdb_cursor_put(m_cur_output_keys, &k, &data, MDB_APPEND))
       throw0(DB_ERROR("Failed to add output pubkey to db transaction"));
   }
   else
@@ -2615,7 +2615,7 @@ void BlockchainLMDB::set_hard_fork_starting_height(uint8_t version, uint64_t hei
 
   MDB_val_copy<uint8_t> val_key(version);
   MDB_val_copy<uint64_t> val_value(height);
-  if (auto result = mdb_put(*txn_ptr, m_hf_starting_heights, &val_key, &val_value, 0))
+  if (auto result = mdb_put(*txn_ptr, m_hf_starting_heights, &val_key, &val_value, MDB_APPEND))
     throw1(DB_ERROR(std::string("Error adding hard fork starting height to db transaction: ").append(mdb_strerror(result)).c_str()));
 
   TXN_BLOCK_POSTFIX_SUCCESS();
@@ -2650,7 +2650,11 @@ void BlockchainLMDB::set_hard_fork_version(uint64_t height, uint8_t version)
 
   MDB_val_copy<uint64_t> val_key(height);
   MDB_val_copy<uint8_t> val_value(version);
-  if (auto result = mdb_put(*txn_ptr, m_hf_versions, &val_key, &val_value, 0))
+  int result;
+  result = mdb_put(*txn_ptr, m_hf_versions, &val_key, &val_value, MDB_APPEND);
+  if (result == MDB_KEYEXIST)
+    result = mdb_put(*txn_ptr, m_hf_versions, &val_key, &val_value, 0);
+  if (result)
     throw1(DB_ERROR(std::string("Error adding hard fork version to db transaction: ").append(mdb_strerror(result)).c_str()));
 
   TXN_BLOCK_POSTFIX_SUCCESS();