Add store prune method.

Author: evoskuil

include/bitcoin/database/impl/store.ipp

@@ -418,6 +418,61 @@ code CLASS::open(const event_handler& handler) NOEXCEPT
     return ec;
 }
 
+TEMPLATE
+code CLASS::prune(const event_handler& handler) NOEXCEPT
+{
+    while (!transactor_mutex_.try_lock_for(std::chrono::seconds(1)))
+    {
+        handler(event_t::wait_lock, table_t::store);
+    }
+
+    code ec{ error::success };
+    const auto prune = [&handler](code& ec, auto& storage, table_t table) NOEXCEPT
+    {
+        if (!ec)
+        {
+            handler(event_t::prune_table, table);
+            if (!storage.reset())
+                ec = error::prune_table;
+        }
+    };
+
+    const auto unload = [&handler](code& ec, auto& storage, table_t table) NOEXCEPT
+    {
+        if (!ec)
+        {
+            handler(event_t::unload_file, table);
+            ec = storage.unload();
+        }
+    };
+
+    const auto load = [&handler](code& ec, auto& storage, table_t table) NOEXCEPT
+    {
+        if (!ec)
+        {
+            handler(event_t::load_file, table);
+            ec = storage.load();
+        }
+    };
+
+    // Prevouts resettable if all candidates confirmed (fork is candidate top).
+    const query<CLASS> query_{ *this };
+    if (query_.get_fork() == query_.get_top_candidate())
+    {
+        // zeroize table head, set body logical size to zero.
+        prune(ec, prevout, table_t::prevout_table);
+
+        // unmap body, setting mapped size to logical size (zero).
+        unload(ec, prevout_body_, table_t::prevout_body);
+
+        // map body, making table usable again.
+        load(ec, prevout_body_, table_t::prevout_body);
+    }
+
+    transactor_mutex_.unlock();
+    return ec;
+}
+
 TEMPLATE
 code CLASS::snapshot(const event_handler& handler) NOEXCEPT
 {

include/bitcoin/database/store.hpp

@@ -63,6 +63,9 @@ class store
     /// Open and load the set of tables, set locks.
     code open(const event_handler& handler) NOEXCEPT;
 
+    /// Prune prunable tables (from loaded, leaves loaded).
+    code prune(const event_handler& handler) NOEXCEPT;
+
     /// Snapshot the set of tables (from loaded, leaves loaded).
     code snapshot(const event_handler& handler) NOEXCEPT;
 

test/store.cpp

@@ -17,6 +17,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #include "test.hpp"
+#include "mocks/blocks.hpp"
 #include "mocks/map_store.hpp"
 
  // these are the slow tests (mmap)
@@ -274,6 +275,22 @@ BOOST_AUTO_TEST_CASE(store__open__created__success)
     BOOST_REQUIRE(!instance.close(events));
 }
 
+// prune
+// ----------------------------------------------------------------------------
+// Empty store asserts so create and initialize.
+
+BOOST_AUTO_TEST_CASE(store__prune__initialized__success)
+{
+    settings configuration{};
+    configuration.path = TEST_DIRECTORY;
+    store<map> instance{ configuration };
+    query<store<map>> query_{ instance };
+    BOOST_REQUIRE(!instance.create(events));
+    BOOST_REQUIRE(query_.initialize(test::genesis));
+    BOOST_REQUIRE(!instance.prune(events));
+    BOOST_REQUIRE(!instance.close(events));
+}
+
 // snapshot
 // ----------------------------------------------------------------------------