Add Env::max_key_size() method to determine the max supported key len…

…gth.

This calls the LMDB mdb_env_get_maxkeysize function.

heed/src/env.rs

@@ -901,6 +901,14 @@ impl Env {
  mdb_result(unsafe { ffi::mdb_env_set_mapsize(self.env_mut_ptr(), new_size) })
  .map_err(Into::into)
  }
+
+ /// Get the maximum size of keys and MDB_DUPSORT data we can write.
+ ///
+ /// Depends on the compile-time constant MDB_MAXKEYSIZE. Default 511
+ pub fn max_key_size(&self) -> usize {
+ let maxsize: i32 = unsafe { ffi::mdb_env_get_maxkeysize(self.env_mut_ptr()) };
+ maxsize as usize
+ }
 }
 
 /// Contains information about the environment.
@@ -1251,4 +1259,21 @@ mod tests {
  env.prepare_for_closing().wait();
  }
  }
+
+ #[test]
+ fn max_key_size() {
+ let dir = tempfile::tempdir().unwrap();
+ let env = unsafe { EnvOpenOptions::new().open(dir.path().join(dir.path())).unwrap() };
+ let maxkeysize = env.max_key_size();
+
+ eprintln!("maxkeysize: {}", maxkeysize);
+
+ if cfg!(feature = "longer-keys") {
+ // Should be larger than the default of 511
+ assert!(maxkeysize > 511);
+ } else {
+ // Should be the default of 511
+ assert_eq!(maxkeysize, 511);
+ }
+ }
 }

heed/src/mdb/lmdb_ffi.rs

@@ -3,11 +3,12 @@ use std::ptr;
 pub use ffi::{
  mdb_cursor_close, mdb_cursor_del, mdb_cursor_get, mdb_cursor_open, mdb_cursor_put,
  mdb_dbi_open, mdb_del, mdb_drop, mdb_env_close, mdb_env_copyfd2, mdb_env_create,
- mdb_env_get_fd, mdb_env_get_flags, 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_stat, mdb_txn_abort,
- mdb_txn_begin, mdb_txn_commit, mdb_version, MDB_cursor, MDB_dbi, MDB_env, MDB_stat, MDB_txn,
- MDB_val, MDB_CP_COMPACT, MDB_CURRENT, MDB_RDONLY, MDB_RESERVE,
+ mdb_env_get_fd, mdb_env_get_flags, mdb_env_get_maxkeysize, 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_stat, mdb_txn_abort, mdb_txn_begin, mdb_txn_commit, mdb_version,
+ MDB_cursor, MDB_dbi, MDB_env, MDB_stat, MDB_txn, MDB_val, MDB_CP_COMPACT, MDB_CURRENT,
+ MDB_RDONLY, MDB_RESERVE,
 };
 use lmdb_master_sys as ffi;