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BlockchainBDB: When removing, find amount output index fast by starting at end

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This improves blockchain reorganization time by allowing one of the more
expensive DB lookups when popping a block to not have to seek through a
long dup list in the "output_amounts" db. This is most noticeable for
HDDs.

See ffcf6bdb95
This commit is contained in:
warptangent 2016-01-28 16:47:27 -08:00
parent 1a5c3fa729
commit b8707466e2
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GPG Key ID: 0E490BEBFBE4E92D
1 changed files with 33 additions and 10 deletions
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43
src/blockchain_db/berkeleydb/db_bdb.cpp
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@ -514,20 +514,43 @@ void BlockchainBDB::remove_amount_output_index(const uint64_t amount, const uint
db_recno_t num_elems = 0; db_recno_t num_elems = 0;
cur->count(&num_elems, 0); cur->count(&num_elems, 0);
// workaround for Berkeley DB to start at end of k's duplicate list:
// if next key exists:
// - move cursor to start of next key's duplicate list, then move back one
// duplicate element to reach the end of the original key's duplicate
// list.
//
// else if the next key doesn't exist:
// - that means we're already on the last key.
// - move cursor to last element in the db, which is the last element of
// the desired key's duplicate list.
result = cur->get(&k, &v, DB_NEXT_NODUP);
if (result != 0 && result != DB_NOTFOUND)
throw0(DB_ERROR("DB error attempting to get next non-duplicate output amount"));
if (result == 0)
result = cur->get(&k, &v, DB_PREV);
else if (result == DB_NOTFOUND)
result = cur->get(&k, &v, DB_LAST);
bool found_index = false;
uint64_t amount_output_index = 0; uint64_t amount_output_index = 0;
uint64_t goi = 0; uint64_t goi = 0;
bool found_index = false;
for (uint64_t i = 0; i < num_elems; ++i) for (uint64_t i = num_elems; i > 0; --i)
{ {
goi = v; goi = v;
if (goi == global_output_index) if (goi == global_output_index)
{ {
amount_output_index = i; amount_output_index = i-1;
found_index = true; found_index = true;
break; break;
} }
cur->get(&k, &v, DB_NEXT_DUP); if (i > 1)
cur->get(&k, &v, DB_PREV_DUP);
} }
if (found_index) if (found_index)
{ {
// found the amount output index // found the amount output index