Makes RocksDB reads faster

Avoids an unneeded copy

lib/src/store/rocksdb.rs

@@ -449,10 +449,13 @@ impl Iterator for SPOGIndexIterator {
 
     fn next(&mut self) -> Option<Result<EncodedQuad>> {
         self.iter.next();
+        unsafe {
+            //This is safe because we are not keeping the buffer
             self.iter
-            .key()
+                .key_inner()
                 .map(|buffer| Cursor::new(buffer).read_spog_quad())
         }
+    }
 }
 
 pub struct POSGIndexIterator {
@@ -464,10 +467,13 @@ impl Iterator for POSGIndexIterator {
 
     fn next(&mut self) -> Option<Result<EncodedQuad>> {
         self.iter.next();
+        unsafe {
+            //This is safe because we are not keeping the buffer
             self.iter
-            .key()
+                .key_inner()
                 .map(|buffer| Cursor::new(buffer).read_posg_quad())
         }
+    }
 }
 
 pub struct OSPGIndexIterator {
@@ -479,10 +485,13 @@ impl Iterator for OSPGIndexIterator {
 
     fn next(&mut self) -> Option<Result<EncodedQuad>> {
         self.iter.next();
+        unsafe {
+            //This is safe because we are not keeping the buffer
             self.iter
-            .key()
+                .key_inner()
                 .map(|buffer| Cursor::new(buffer).read_ospg_quad())
         }
+    }
 }
 
 pub struct FilteringEncodedQuadsIterator<I: Iterator<Item = Result<EncodedQuad>>> {