Keep Cache and Env alive with Rc (#497)

src/checkpoint.rs

@@ -19,23 +19,25 @@
 
 use crate::{ffi, Error, DB};
 use std::ffi::CString;
+use std::marker::PhantomData;
 use std::path::Path;
 
 /// Undocumented parameter for `ffi::rocksdb_checkpoint_create` function. Zero by default.
 const LOG_SIZE_FOR_FLUSH: u64 = 0_u64;
 
 /// Database's checkpoint object.
 /// Used to create checkpoints of the specified DB from time to time.
-pub struct Checkpoint {
+pub struct Checkpoint<'db> {
     inner: *mut ffi::rocksdb_checkpoint_t,
+    _db: PhantomData<&'db ()>,
 }
 
-impl Checkpoint {
+impl<'db> Checkpoint<'db> {
     /// Creates new checkpoint object for specific DB.
     ///
     /// Does not actually produce checkpoints, call `.create_checkpoint()` method to produce
     /// a DB checkpoint.
-    pub fn new(db: &DB) -> Result<Checkpoint, Error> {
+    pub fn new(db: &'db DB) -> Result<Checkpoint<'db>, Error> {
         let checkpoint: *mut ffi::rocksdb_checkpoint_t;
 
         unsafe { checkpoint = ffi_try!(ffi::rocksdb_checkpoint_object_create(db.inner)) };
@@ -44,7 +46,10 @@ impl Checkpoint {
             return Err(Error::new("Could not create checkpoint object.".to_owned()));
         }
 
-        Ok(Checkpoint { inner: checkpoint })
+        Ok(Checkpoint {
+            inner: checkpoint,
+            _db: PhantomData,
+        })
     }
 
     /// Creates new physical DB checkpoint in directory specified by `path`.
@@ -70,7 +75,7 @@ impl Checkpoint {
     }
 }
 
-impl Drop for Checkpoint {
+impl<'db> Drop for Checkpoint<'db> {
     fn drop(&mut self) {
         unsafe {
             ffi::rocksdb_checkpoint_object_destroy(self.inner);

src/db.rs

@@ -16,6 +16,7 @@
 use crate::{
     column_family::AsColumnFamilyRef,
     column_family::BoundColumnFamily,
+    db_options::OptionsMustOutliveDB,
     ffi,
     ffi_util::{from_cstr, opt_bytes_to_ptr, raw_data, to_cpath},
     ColumnFamily, ColumnFamilyDescriptor, CompactOptions, DBIteratorWithThreadMode,
@@ -29,6 +30,7 @@ use std::collections::BTreeMap;
 use std::ffi::{CStr, CString};
 use std::fmt;
 use std::fs;
+use std::iter;
 use std::marker::PhantomData;
 use std::path::Path;
 use std::path::PathBuf;
@@ -102,6 +104,7 @@ pub struct DBWithThreadMode<T: ThreadMode> {
     pub(crate) inner: *mut ffi::rocksdb_t,
     cfs: T, // Column families are held differently depending on thread mode
     path: PathBuf,
+    _outlive: Vec<OptionsMustOutliveDB>,
 }
 
 /// Minimal set of DB-related methods, intended to be  generic over
@@ -238,6 +241,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
             inner: db,
             cfs: T::new(BTreeMap::new()),
             path: path.as_ref().to_path_buf(),
+            _outlive: vec![opts.outlive.clone()],
         })
     }
 
@@ -330,6 +334,9 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         I: IntoIterator<Item = ColumnFamilyDescriptor>,
     {
         let cfs: Vec<_> = cfs.into_iter().collect();
+        let outlive = iter::once(opts.outlive.clone())
+            .chain(cfs.iter().map(|cf| cf.options.outlive.clone()))
+            .collect();
 
         let cpath = to_cpath(&path)?;
 
@@ -401,6 +408,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
             inner: db,
             path: path.as_ref().to_path_buf(),
             cfs: T::new(cf_map),
+            _outlive: outlive,
         })
     }