Add database level stat function

src/environment.rs

@@ -161,7 +161,7 @@ impl Environment {
     /// Retrieves statistics about this environment.
     pub fn stat(&self) -> Result<Stat> {
         unsafe {
-            let mut stat = Stat(mem::zeroed());
+            let mut stat = Stat::new();
             lmdb_try!(ffi::mdb_env_stat(self.env(), &mut stat.0));
             Ok(stat)
         }
@@ -248,7 +248,16 @@ impl Environment {
 /// Environment statistics.
 ///
 /// Contains information about the size and layout of an LMDB environment.
-pub struct Stat(ffi::MDB_stat);
+pub struct Stat(pub(crate) ffi::MDB_stat);
+
+impl Stat {
+    /// Create a new Stat with zero'd inner struct `ffi::MDB_stat`.
+    pub fn new() -> Stat {
+        unsafe {
+            Stat(mem::zeroed())
+        }
+    }
+}
 
 impl Stat {
     /// Size of a database page. This is the same for all databases in the environment.

src/transaction.rs

@@ -5,7 +5,7 @@ use std::marker::PhantomData ;
 use ffi;
 
 use cursor::{RoCursor, RwCursor};
-use environment::Environment;
+use environment::{Environment, Stat};
 use database::Database;
 use error::{Error, Result, lmdb_result};
 use flags::{DatabaseFlags, EnvironmentFlags, WriteFlags};
@@ -102,6 +102,15 @@ pub trait Transaction : Sized {
         }
         Ok(DatabaseFlags::from_bits_truncate(flags))
     }
+
+    /// Retrieves database statistics.
+    fn stat(&self, db: Database) -> Result<Stat> {
+        unsafe {
+            let mut stat = Stat::new();
+            lmdb_try!(ffi::mdb_stat(self.txn(), db.dbi(), &mut stat.0));
+            Ok(stat)
+        }
+    }
 }
 
 /// An LMDB read-only transaction.
@@ -654,6 +663,96 @@ mod test {
         }
     }
 
+    #[test]
+    fn test_stat() {
+        let dir = TempDir::new("test").unwrap();
+        let env = Environment::new().open(dir.path()).unwrap();
+        let db = env.create_db(None, DatabaseFlags::empty()).unwrap();
+
+        let mut txn = env.begin_rw_txn().unwrap();
+        txn.put(db, b"key1", b"val1", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key2", b"val2", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key3", b"val3", WriteFlags::empty()).unwrap();
+        txn.commit().unwrap();
+
+        {
+            let txn = env.begin_ro_txn().unwrap();
+            let stat = txn.stat(db).unwrap();
+            assert_eq!(stat.entries(), 3);
+        }
+
+        let mut txn = env.begin_rw_txn().unwrap();
+        txn.del(db, b"key1", None).unwrap();
+        txn.del(db, b"key2", None).unwrap();
+        txn.commit().unwrap();
+
+        {
+            let txn = env.begin_ro_txn().unwrap();
+            let stat = txn.stat(db).unwrap();
+            assert_eq!(stat.entries(), 1);
+        }
+
+        let mut txn = env.begin_rw_txn().unwrap();
+        txn.put(db, b"key4", b"val4", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key5", b"val5", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key6", b"val6", WriteFlags::empty()).unwrap();
+        txn.commit().unwrap();
+
+        {
+            let txn = env.begin_ro_txn().unwrap();
+            let stat = txn.stat(db).unwrap();
+            assert_eq!(stat.entries(), 4);
+        }
+    }
+
+    #[test]
+    fn test_stat_dupsort() {
+        let dir = TempDir::new("test").unwrap();
+        let env = Environment::new().open(dir.path()).unwrap();
+        let db = env.create_db(None, DatabaseFlags::DUP_SORT).unwrap();
+
+        let mut txn = env.begin_rw_txn().unwrap();
+        txn.put(db, b"key1", b"val1", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key1", b"val2", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key1", b"val3", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key2", b"val1", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key2", b"val2", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key2", b"val3", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key3", b"val1", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key3", b"val2", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key3", b"val3", WriteFlags::empty()).unwrap();
+        txn.commit().unwrap();
+
+        {
+            let txn = env.begin_ro_txn().unwrap();
+            let stat = txn.stat(db).unwrap();
+            assert_eq!(stat.entries(), 9);
+        }
+
+        let mut txn = env.begin_rw_txn().unwrap();
+        txn.del(db, b"key1", Some(b"val2")).unwrap();
+        txn.del(db, b"key2", None).unwrap();
+        txn.commit().unwrap();
+
+        {
+            let txn = env.begin_ro_txn().unwrap();
+            let stat = txn.stat(db).unwrap();
+            assert_eq!(stat.entries(), 5);
+        }
+
+        let mut txn = env.begin_rw_txn().unwrap();
+        txn.put(db, b"key4", b"val1", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key4", b"val2", WriteFlags::empty()).unwrap();
+        txn.put(db, b"key4", b"val3", WriteFlags::empty()).unwrap();
+        txn.commit().unwrap();
+
+        {
+            let txn = env.begin_ro_txn().unwrap();
+            let stat = txn.stat(db).unwrap();
+            assert_eq!(stat.entries(), 8);
+        }
+    }
+
     #[bench]
     fn bench_get_rand(b: &mut Bencher) {
         let n = 100u32;