Expose env stats

heed/src/envs/encrypted_env.rs

@@ -8,6 +8,7 @@ use aead::{AeadMutInPlace, Key, KeyInit, Nonce, Tag};
 
 use super::{Env, EnvClosingEvent, EnvInfo, FlagSetMode};
 use crate::databases::{EncryptedDatabase, EncryptedDatabaseOpenOptions};
+use crate::envs::EnvStat;
 use crate::mdb::ffi::{self};
 use crate::{CompactionOption, EnvFlags, Result, RoTxn, RwTxn, Unspecified, WithTls};
 #[allow(unused)] // fro cargo auto doc links
@@ -93,6 +94,11 @@ impl<T> EncryptedEnv<T> {
         self.inner.info()
     }
 
+    /// Returns some statistics about this environment.
+    pub fn stat(&self) -> EnvStat {
+        self.inner.stat()
+    }
+
     /// Returns the size used by all the databases in the environment without the free pages.
     ///
     /// It is crucial to configure [`EnvOpenOptions::max_dbs`] with a sufficiently large value

heed/src/envs/env.rs

@@ -16,6 +16,7 @@ use super::{
     EnvInfo, FlagSetMode, IntegerComparator, OPENED_ENV,
 };
 use crate::cursor::{MoveOperation, RoCursor};
+use crate::envs::EnvStat;
 use crate::mdb::ffi::{self, MDB_env};
 use crate::mdb::lmdb_error::mdb_result;
 use crate::mdb::lmdb_flags::AllDatabaseFlags;
@@ -136,15 +137,47 @@ impl<T> Env<T> {
     pub fn info(&self) -> EnvInfo {
         let mut raw_info = mem::MaybeUninit::uninit();
         unsafe { ffi::mdb_env_info(self.inner.env_ptr.as_ptr(), raw_info.as_mut_ptr()) };
-        let raw_info = unsafe { raw_info.assume_init() };
+        let ffi::MDB_envinfo {
+            me_mapaddr,
+            me_mapsize,
+            me_last_pgno,
+            me_last_txnid,
+            me_maxreaders,
+            me_numreaders,
+        } = unsafe { raw_info.assume_init() };
 
         EnvInfo {
-            map_addr: raw_info.me_mapaddr,
-            map_size: raw_info.me_mapsize,
-            last_page_number: raw_info.me_last_pgno,
-            last_txn_id: raw_info.me_last_txnid,
-            maximum_number_of_readers: raw_info.me_maxreaders,
-            number_of_readers: raw_info.me_numreaders,
+            map_addr: me_mapaddr,
+            map_size: me_mapsize,
+            last_page_number: me_last_pgno,
+            last_txn_id: me_last_txnid,
+            maximum_number_of_readers: me_maxreaders,
+            number_of_readers: me_numreaders,
+        }
+    }
+
+    /// Returns some statistics about this environment.
+    pub fn stat(&self) -> EnvStat {
+        let mut raw_stat = mem::MaybeUninit::uninit();
+        unsafe { ffi::mdb_env_stat(self.inner.env_ptr.as_ptr(), raw_stat.as_mut_ptr()) };
+        // SAFETY: `mdb_env_stat` can only ever return EINVAL, and only if `env` or `stat` are null,
+        // which cannot be the case here as `raw_stat` is on the stack, and `env` is a `NonNull`.
+        let ffi::MDB_stat {
+            ms_psize,
+            ms_depth,
+            ms_branch_pages,
+            ms_leaf_pages,
+            ms_overflow_pages,
+            ms_entries,
+        } = unsafe { raw_stat.assume_init() };
+
+        EnvStat {
+            page_size: ms_psize,
+            depth: ms_depth,
+            branch_pages: ms_branch_pages,
+            leaf_pages: ms_leaf_pages,
+            overflow_pages: ms_overflow_pages,
+            entries: ms_entries,
         }
     }
 

heed/src/envs/mod.rs

@@ -62,6 +62,24 @@ pub struct EnvInfo {
     pub number_of_readers: u32,
 }
 
+/// Statistics for an environment.
+#[derive(Debug, Clone, Copy)]
+pub struct EnvStat {
+    /// Size of a database page.
+    /// This is currently the same for all databases.
+    pub page_size: u32,
+    /// Depth (height) of the B-tree.
+    pub depth: u32,
+    /// Number of internal (non-leaf) pages
+    pub branch_pages: usize,
+    /// Number of leaf pages.
+    pub leaf_pages: usize,
+    /// Number of overflow pages.
+    pub overflow_pages: usize,
+    /// Number of data items.
+    pub entries: usize,
+}
+
 /// A structure that can be used to wait for the closing event.
 /// Multiple threads can wait on this event.
 #[derive(Clone)]

heed/src/mdb/lmdb_ffi.rs

@@ -7,8 +7,8 @@ pub use ffi::{
     mdb_env_info, mdb_env_open, mdb_env_set_flags, mdb_env_set_mapsize, mdb_env_set_maxdbs,
     mdb_env_set_maxreaders, mdb_env_stat, mdb_env_sync, mdb_filehandle_t, mdb_get, mdb_put,
     mdb_reader_check, mdb_set_compare, mdb_set_dupsort, mdb_stat, mdb_txn_abort, mdb_txn_begin,
-    mdb_txn_commit, mdb_txn_id, mdb_version, MDB_cursor, MDB_dbi, MDB_env, MDB_stat, MDB_txn,
-    MDB_val, MDB_CP_COMPACT, MDB_CURRENT, MDB_RDONLY, MDB_RESERVE,
+    mdb_txn_commit, mdb_txn_id, mdb_version, MDB_cursor, MDB_dbi, MDB_env, MDB_envinfo, MDB_stat,
+    MDB_txn, MDB_val, MDB_CP_COMPACT, MDB_CURRENT, MDB_RDONLY, MDB_RESERVE,
 };
 #[cfg(master3)]
 pub use ffi::{mdb_env_set_encrypt, MDB_enc_func};