add Guard::into_inner_if

Author: marvin-j97

src/blob_tree/mod.rs

@@ -32,6 +32,24 @@ pub struct Guard {
 }
 
 impl IterGuard for Guard {
+    fn into_inner_if(self, pred: impl Fn(&[u8]) -> bool) -> crate::Result<Option<crate::KvPair>> {
+        let kv = self.kv?;
+
+        if pred(&kv.key.user_key) {
+            resolve_value_handle(
+                self.tree.id(),
+                self.tree.blobs_folder.as_path(),
+                &self.tree.index.config.cache,
+                &self.tree.index.config.descriptor_table,
+                &self.version,
+                kv,
+            )
+            .map(Some)
+        } else {
+            Ok(None)
+        }
+    }
+
     fn key(self) -> crate::Result<UserKey> {
         self.kv.map(|kv| kv.key.user_key)
     }

src/iter_guard.rs

@@ -6,6 +6,16 @@ use enum_dispatch::enum_dispatch;
 /// Guard to access key-value pairs
 #[enum_dispatch]
 pub trait IterGuard {
+    /// Accesses the key-value pair if the predicate returns `true`.
+    ///
+    /// The predicate receives the key - if returning false, the value
+    /// may not be loaded if the tree is key-value separated.
+    ///
+    /// # Errors
+    ///
+    /// Will return `Err` if an IO error occurs.
+    fn into_inner_if(self, pred: impl Fn(&[u8]) -> bool) -> crate::Result<Option<KvPair>>;
+
     /// Accesses the key-value pair.
     ///
     /// # Errors

src/tree/mod.rs

@@ -36,6 +36,16 @@ use crate::metrics::Metrics;
 pub struct Guard(crate::Result<(UserKey, UserValue)>);
 
 impl IterGuard for Guard {
+    fn into_inner_if(self, pred: impl Fn(&[u8]) -> bool) -> crate::Result<Option<KvPair>> {
+        let (k, v) = self.0?;
+
+        if pred(&k) {
+            Ok(Some((k, v)))
+        } else {
+            Ok(None)
+        }
+    }
+
     fn key(self) -> crate::Result<UserKey> {
         self.0.map(|(k, _)| k)
     }