Add methods to clear SQLiteReader instances

Author: Hendrik van Antwerpen

stack-graphs/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+- New `SQLiteReader::clear` and `SQLiteReader::clear_paths` methods that make it easier to reuse instances.
+
 ### Changed
 
 - The `Appendable` trait has been simplified. Its `Ctx` type parameter is gone, in favor of a separate trait `ToAppendable` that is used to find appendables for a handle. The type itself moved from the `cycles` to the `stitching` module.

stack-graphs/src/arena.rs

@@ -181,6 +181,13 @@ impl<T> Arena<T> {
         }
     }
 
+    /// Clear the arena, keeping underlying allocated capacity.  After this, all previous handles into
+    /// the arena are invalid.
+    #[inline(always)]
+    pub(crate) fn clear(&mut self) {
+        self.items.clear();
+    }
+
     /// Adds a new instance to this arena, returning a stable handle to it.
     ///
     /// Note that we do not deduplicate instances of `T` in any way.  If you add two instances that
@@ -280,6 +287,13 @@ impl<H, T> SupplementalArena<H, T> {
         }
     }
 
+    /// Clear the supplemantal arena, keeping underlying allocated capacity.  After this,
+    /// all previous handles into the arena are invalid.
+    #[inline(always)]
+    pub(crate) fn clear(&mut self) {
+        self.items.clear();
+    }
+
     /// Creates a new, empty supplemental arena, preallocating enough space to store supplemental
     /// data for all of the instances that have already been allocated in a (regular) arena.
     pub fn with_capacity(arena: &Arena<H>) -> SupplementalArena<H, T> {

stack-graphs/src/partial.rs

@@ -2624,4 +2624,10 @@ impl PartialPaths {
             partial_path_edges: Deque::new_arena(),
         }
     }
+
+    pub(crate) fn clear(&mut self) {
+        self.partial_symbol_stacks.clear();
+        self.partial_scope_stacks.clear();
+        self.partial_path_edges.clear();
+    }
 }

stack-graphs/src/stitching.rs

@@ -249,6 +249,17 @@ impl Database {
         }
     }
 
+    /// Clear the database.  After this, all previous handles into the database are
+    /// invalid.
+    pub(crate) fn clear(&mut self) {
+        self.partial_paths.clear();
+        self.local_nodes.clear();
+        self.symbol_stack_keys.clear();
+        self.symbol_stack_key_cache.clear();
+        self.paths_by_start_node.clear();
+        self.root_paths_by_precondition.clear();
+    }
+
     /// Adds a partial path to this database.  We do not deduplicate partial paths in any way; it's
     /// your responsibility to only add each partial path once.
     pub fn add_partial_path(

stack-graphs/src/storage.rs

@@ -447,6 +447,28 @@ impl SQLiteReader {
         })
     }
 
+    /// Clear all data that has been loaded into this reader instance.
+    /// After this call, all existing handles from this reader are invalid.
+    pub fn clear(&mut self) {
+        self.loaded_graphs.clear();
+        self.graph = StackGraph::new();
+
+        self.loaded_node_paths.clear();
+        self.loaded_root_paths.clear();
+        self.partials.clear();
+        self.db.clear();
+    }
+
+    /// Clear path data that has been loaded into this reader instance.
+    /// After this call, all node handles remain valid, but all path data
+    /// is invalid.
+    pub fn clear_paths(&mut self) {
+        self.loaded_node_paths.clear();
+        self.loaded_root_paths.clear();
+        self.partials.clear();
+        self.db.clear();
+    }
+
     /// Get the file's status in the database. If a tag is provided, it must match or the file
     /// is reported missing.
     pub fn status_for_file<T: AsRef<str>>(