Unable to create database when MDB_WRITEMAP is set

[akhilles]

To reproduce:

let path = Path::new("target").join("test.mdb");
fs::create_dir_all(&path)?;
let mut env_builder = EnvOpenOptions::new();
unsafe {
    env_builder.flag(Flags::MdbNoSync);
    env_builder.flag(Flags::MdbWriteMap);
}
let env = env_builder.map_size(10 * 1024 * 1024 * 1024).max_dbs(1000).open(path)?;
let db: Database<ByteSlice, Unit> = env.create_database(Some("test"))?;

fails with:

Error: Mdb(BadTxn)

Works fine if env_builder.flag(Flags::MdbWriteMap); is commented out.

[Kerollmops]

Hey, I am not sure why as I only call the LMDB methods under the hood.

[akhilles]

Hey, I am not sure why as I only call the LMDB methods under the hood.

Will try to reproduce using only the C library.

[akhilles]

Wasn't able to reproduce using the C library. I think the issue is with nested write transactions. The following patch fixes the issue:

diff --git a/heed/src/env.rs b/heed/src/env.rs
index a8305c5..d126cc9 100644
--- a/heed/src/env.rs
+++ b/heed/src/env.rs
@@ -318,23 +318,20 @@ impl Env {
         KC: 'static,
         DC: 'static,
     {
-        let mut parent_wtxn = self.write_txn()?;
-        let db = self.create_database_with_txn(name, &mut parent_wtxn)?;
-        parent_wtxn.commit()?;
+        let db = self.create_database_with_txn(name)?;
         Ok(db)
     }
 
     pub fn create_database_with_txn<KC, DC>(
         &self,
         name: Option<&str>,
-        parent_wtxn: &mut RwTxn,
     ) -> Result<Database<KC, DC>>
     where
         KC: 'static,
         DC: 'static,
     {
         let types = (TypeId::of::<KC>(), TypeId::of::<DC>());
-        self.raw_create_database(name, types, parent_wtxn)
+        self.raw_create_database(name, types)
             .map(|db| Database::new(self.env_mut_ptr() as _, db))
     }
 
@@ -342,9 +339,8 @@ impl Env {
         &self,
         name: Option<&str>,
         types: (TypeId, TypeId),
-        parent_wtxn: &mut RwTxn,
     ) -> Result<u32> {
-        let wtxn = self.nested_write_txn(parent_wtxn)?;
+        let wtxn = self.write_txn()?;
 
         let mut dbi = 0;
         let name = name.map(|n| CString::new(n).unwrap());

[Kerollmops]

@timokoesters that's indeed a duplicate of the the issue you opened recently but I have no plan to fix it.

Maybe you could submit a PR, it you do please make sur to start from the right branch (v0.12). It depends on the version you were using you could also start from v0.11.

[Kerollmops]

Closed by #128.