1 files changed, 153 insertions, 0 deletions
diff --git a/src/db/open.rs b/src/db/open.rs
new file mode 100644
index 00000000..ae135c4e
--- /dev/null
+++ b/src/db/open.rs
@@ -0,0 +1,153 @@
+use std::path::PathBuf;
+
+use crate::{Db, Error, Result};
+
+/// List of supported database engine types
+///
+/// The `enum` holds list of *all* database engines that are are be supported by crate, no matter
+/// if relevant feature is enabled or not. It allows us to distinguish between invalid engine
+/// and valid engine, whose support is not enabled via feature flag.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Engine {
+	Lmdb,
+	Sqlite,
+	Sled,
+}
+
+impl Engine {
+	/// Return variant name as static `&str`
+	pub fn as_str(&self) -> &'static str {
+		match self {
+			Self::Lmdb => "lmdb",
+			Self::Sqlite => "sqlite",
+			Self::Sled => "sled",
+		}
+	}
+}
+
+impl std::fmt::Display for Engine {
+	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+		self.as_str().fmt(fmt)
+	}
+}
+
+impl std::str::FromStr for Engine {
+	type Err = Error;
+
+	fn from_str(text: &str) -> Result<Engine> {
+		match text {
+			"lmdb" | "heed" => Ok(Self::Lmdb),
+			"sqlite" | "sqlite3" | "rusqlite" => Ok(Self::Sqlite),
+			"sled" => Ok(Self::Sled),
+			kind => Err(Error(
+				format!(
+					"Invalid DB engine: {} (options are: lmdb, sled, sqlite)",
+					kind
+				)
+				.into(),
+			)),
+		}
+	}
+}
+
+pub struct OpenOpt {
+	pub fsync: bool,
+	pub lmdb_map_size: Option<usize>,
+	pub sled_cache_capacity: usize,
+	pub sled_flush_every_ms: u64,
+}
+
+impl Default for OpenOpt {
+	fn default() -> Self {
+		Self {
+			fsync: false,
+			lmdb_map_size: None,
+			sled_cache_capacity: 1024 * 1024 * 1024,
+			sled_flush_every_ms: 2000,
+		}
+	}
+}
+
+pub fn open_db(path: &PathBuf, engine: Engine, opt: &OpenOpt) -> Result<Db> {
+	match engine {
+		// ---- Sled DB ----
+		#[cfg(feature = "sled")]
+		Engine::Sled => {
+			if opt.fsync {
+				return Err(Error(
+					"`metadata_fsync = true` is not supported with the Sled database engine".into(),
+				));
+			}
+			info!("Opening Sled database at: {}", path.display());
+			let db = crate::sled_adapter::sled::Config::default()
+				.path(&path)
+				.cache_capacity(opt.sled_cache_capacity as u64)
+				.flush_every_ms(Some(opt.sled_flush_every_ms))
+				.open()?;
+			Ok(crate::sled_adapter::SledDb::init(db))
+		}
+
+		// ---- Sqlite DB ----
+		#[cfg(feature = "sqlite")]
+		Engine::Sqlite => {
+			info!("Opening Sqlite database at: {}", path.display());
+			let db = crate::sqlite_adapter::rusqlite::Connection::open(&path)?;
+			db.pragma_update(None, "journal_mode", "WAL")?;
+			if opt.fsync {
+				db.pragma_update(None, "synchronous", "NORMAL")?;
+			} else {
+				db.pragma_update(None, "synchronous", "OFF")?;
+			}
+			Ok(crate::sqlite_adapter::SqliteDb::init(db))
+		}
+
+		// ---- LMDB DB ----
+		#[cfg(feature = "lmdb")]
+		Engine::Lmdb => {
+			info!("Opening LMDB database at: {}", path.display());
+			if let Err(e) = std::fs::create_dir_all(&path) {
+				return Err(Error(
+					format!("Unable to create LMDB data directory: {}", e).into(),
+				));
+			}
+
+			let map_size = match opt.lmdb_map_size {
+				None => crate::lmdb_adapter::recommended_map_size(),
+				Some(v) => v - (v % 4096),
+			};
+
+			let mut env_builder = heed::EnvOpenOptions::new();
+			env_builder.max_dbs(100);
+			env_builder.map_size(map_size);
+			env_builder.max_readers(2048);
+			unsafe {
+				env_builder.flag(crate::lmdb_adapter::heed::flags::Flags::MdbNoMetaSync);
+				if !opt.fsync {
+					env_builder.flag(heed::flags::Flags::MdbNoSync);
+				}
+			}
+			match env_builder.open(&path) {
+				Err(heed::Error::Io(e)) if e.kind() == std::io::ErrorKind::OutOfMemory => {
+					return Err(Error(
+						"OutOfMemory error while trying to open LMDB database. This can happen \
+                        if your operating system is not allowing you to use sufficient virtual \
+                        memory address space. Please check that no limit is set (ulimit -v). \
+                        You may also try to set a smaller `lmdb_map_size` configuration parameter. \
+                        On 32-bit machines, you should probably switch to another database engine."
+							.into(),
+					))
+				}
+				Err(e) => Err(Error(format!("Cannot open LMDB database: {}", e).into())),
+				Ok(db) => Ok(crate::lmdb_adapter::LmdbDb::init(db)),
+			}
+		}
+
+		// Pattern is unreachable when all supported DB engines are compiled into binary. The allow
+		// attribute is added so that we won't have to change this match in case stop building
+		// support for one or more engines by default.
+		#[allow(unreachable_patterns)]
+		engine => Err(Error(
+			format!("DB engine support not available in this build: {}", engine).into(),
+		)),
+	}
+}