adding compaction from lib

src/lib.rs

@@ -167,9 +167,52 @@ impl<'a> From<(Bound<Cow<'a, str>>, Bound<Cow<'a, str>>)> for CowStringRange<'a>
 	}
 }
 
+/// Perform a compaction of the DB.
+/// 
+/// Written for use with downstream crates needing periodic
+/// compactions.
+pub fn compact(dir: &std::path::Path, major: bool) -> std::io::Result<()> {
+	use fs2::FileExt;
+	let lock = std::fs::File::create(dir.join(".compact"))?;
+	lock.try_lock_exclusive()?;
+
+	let db = if major {
+		DatabaseReader::new(dir)?
+	} else {
+		DatabaseReader::without_main_db(dir)?
+	};
+
+	let mut no_transaction_paths = false;
+	{
+		let ps = db.transaction_paths();
+		if ps.len() == 1 && ps[0].file_name().expect("filename") == "main" {
+			no_transaction_paths = true;
+		}
+	}
+
+	if db.num_txes() <= 1 || no_transaction_paths {
+		println!("Compaction has nothing to do.");
+	} else {
+		println!("Processing {} .txes", db.num_txes());
+		let db = std::sync::Arc::new(db);
+		let mut compacted = CreateTx::new(dir)?;
+
+		// create the new transaction after opening the database reader
+		let reader = db.get_range(..);
+		let mut n = 0u64;
+		for record in reader {
+			compacted.add_record_raw(record.key(), record.format(), record.raw()).expect("Error adding record");
+			n += 1;
+		}
+		_purge_compacted_files(compacted, dir, &db, major)?;
+		println!("Compacted {} records.", {n});
+	}
+
+	Ok(())
+}
+
 // not part of public api
 #[doc(hidden)]
-#[cfg(feature = "bin")]
 pub fn _purge_compacted_files(
 	compacted: CreateTx,
 	dir: &std::path::Path,