Database Refactor

combine service/users data w/ mod unit

split sliding sync related out of service/users

instrument database entry points

remove increment crap from database interface

de-wrap all database get() calls

de-wrap all database insert() calls

de-wrap all database remove() calls

refactor database interface for async streaming

add query key serializer for database

implement Debug for result handle

add query deserializer for database

add deserialization trait for option handle

start a stream utils suite

de-wrap/asyncify/type-query count_one_time_keys()

de-wrap/asyncify users count

add admin query users command suite

de-wrap/asyncify users exists

de-wrap/partially asyncify user filter related

asyncify/de-wrap users device/keys related

asyncify/de-wrap user auth/misc related

asyncify/de-wrap users blurhash

asyncify/de-wrap account_data get; merge Data into Service

partial asyncify/de-wrap uiaa; merge Data into Service

partially asyncify/de-wrap transaction_ids get; merge Data into Service

partially asyncify/de-wrap key_backups; merge Data into Service

asyncify/de-wrap pusher service getters; merge Data into Service

asyncify/de-wrap rooms alias getters/some iterators

asyncify/de-wrap rooms directory getters/iterator

partially asyncify/de-wrap rooms lazy-loading

partially asyncify/de-wrap rooms metadata

asyncify/dewrap rooms outlier

asyncify/dewrap rooms pdu_metadata

dewrap/partially asyncify rooms read receipt

de-wrap rooms search service

de-wrap/partially asyncify rooms user service

partial de-wrap rooms state_compressor

de-wrap rooms state_cache

de-wrap room state et al

de-wrap rooms timeline service

additional users device/keys related

de-wrap/asyncify sender

asyncify services

refactor database to TryFuture/TryStream

refactor services for TryFuture/TryStream

asyncify api handlers

additional asyncification for admin module

abstract stream related; support reverse streams

additional stream conversions

asyncify state-res related

Signed-off-by: Jason Volk <jason@zemos.net>

src/database/stream.rs

@@ -0,0 +1,122 @@
+mod items;
+mod items_rev;
+mod keys;
+mod keys_rev;
+
+use std::sync::Arc;
+
+use conduit::{utils::exchange, Error, Result};
+use rocksdb::{ColumnFamily, DBRawIteratorWithThreadMode, ReadOptions};
+
+pub(crate) use self::{items::Items, items_rev::ItemsRev, keys::Keys, keys_rev::KeysRev};
+use crate::{
+	engine::Db,
+	keyval::{Key, KeyVal, Val},
+	util::map_err,
+	Engine, Slice,
+};
+
+struct State<'a> {
+	inner: Inner<'a>,
+	seek: bool,
+	init: bool,
+}
+
+trait Cursor<'a, T> {
+	fn state(&self) -> &State<'a>;
+
+	fn fetch(&self) -> Option<T>;
+
+	fn seek(&mut self);
+
+	fn get(&self) -> Option<Result<T>> {
+		self.fetch()
+			.map(Ok)
+			.or_else(|| self.state().status().map(Err))
+	}
+
+	fn seek_and_get(&mut self) -> Option<Result<T>> {
+		self.seek();
+		self.get()
+	}
+}
+
+type Inner<'a> = DBRawIteratorWithThreadMode<'a, Db>;
+type From<'a> = Option<Key<'a>>;
+
+impl<'a> State<'a> {
+	fn new(db: &'a Arc<Engine>, cf: &'a Arc<ColumnFamily>, opts: ReadOptions) -> Self {
+		Self {
+			inner: db.db.raw_iterator_cf_opt(&**cf, opts),
+			init: true,
+			seek: false,
+		}
+	}
+
+	fn init_fwd(mut self, from: From<'_>) -> Self {
+		if let Some(key) = from {
+			self.inner.seek(key);
+			self.seek = true;
+		}
+
+		self
+	}
+
+	fn init_rev(mut self, from: From<'_>) -> Self {
+		if let Some(key) = from {
+			self.inner.seek_for_prev(key);
+			self.seek = true;
+		}
+
+		self
+	}
+
+	fn seek_fwd(&mut self) {
+		if !exchange(&mut self.init, false) {
+			self.inner.next();
+		} else if !self.seek {
+			self.inner.seek_to_first();
+		}
+	}
+
+	fn seek_rev(&mut self) {
+		if !exchange(&mut self.init, false) {
+			self.inner.prev();
+		} else if !self.seek {
+			self.inner.seek_to_last();
+		}
+	}
+
+	fn fetch_key(&self) -> Option<Key<'_>> { self.inner.key().map(Key::from) }
+
+	fn _fetch_val(&self) -> Option<Val<'_>> { self.inner.value().map(Val::from) }
+
+	fn fetch(&self) -> Option<KeyVal<'_>> { self.inner.item().map(KeyVal::from) }
+
+	fn status(&self) -> Option<Error> { self.inner.status().map_err(map_err).err() }
+
+	fn valid(&self) -> bool { self.inner.valid() }
+}
+
+fn keyval_longevity<'a, 'b: 'a>(item: KeyVal<'a>) -> KeyVal<'b> {
+	(slice_longevity::<'a, 'b>(item.0), slice_longevity::<'a, 'b>(item.1))
+}
+
+fn slice_longevity<'a, 'b: 'a>(item: &'a Slice) -> &'b Slice {
+	// SAFETY: The lifetime of the data returned by the rocksdb cursor is only valid
+	// between each movement of the cursor. It is hereby unsafely extended to match
+	// the lifetime of the cursor itself. This is due to the limitation of the
+	// Stream trait where the Item is incapable of conveying a lifetime; this is due
+	// to GAT's being unstable during its development. This unsafety can be removed
+	// as soon as this limitation is addressed by an upcoming version.
+	//
+	// We have done our best to mitigate the implications of this in conjunction
+	// with the deserialization API such that borrows being held across movements of
+	// the cursor do not happen accidentally. The compiler will still error when
+	// values herein produced try to leave a closure passed to a StreamExt API. But
+	// escapes can happen if you explicitly and intentionally attempt it, and there
+	// will be no compiler error or warning. This is primarily the case with
+	// calling collect() without a preceding map(ToOwned::to_owned). A collection
+	// of references here is illegal, but this will not be enforced by the compiler.
+	unsafe { std::mem::transmute(item) }
+}