Add freelist cache.

This commit adds a cache to the freelist which combines the available free pages and pending free pages in
a single map. This was added to improve performance where freelist.isFree() was consuming 70% of CPU time
for large freelists.

1 files changed, 1 insertions, 1 deletions

diff --git a/db_test.go b/db_test.go
index e689836..74ffcb9 100644
--- a/db_test.go
+++ b/db_test.go
@@ -418,7 +418,7 @@ func TestDB_DoubleFree(t *testing.T) {
 		})
 	}()
 
-	assert.Equal(t, "tx 2: page 3 already freed in tx 0", msg)
+	assert.Equal(t, "assertion failed: page 3 already freed", msg)
 }
 
 func ExampleDB_Update() {