Fix key collision for child trie (#4162)

* In progress, runtime io must switch to future proof root +
child_specific (unique id) + u32 type.

* Switch interface, sr-io seems ok, rpc could use similar interface to
sr-io, genesis json broken if there is child trie in existing encoding
genesis.

* test from previous implementation.

* fix proving test.

* Restore Keyspacedb from other branch, only apply to child trie.

* Removing unneeded child_info from child root (child info are stored
if things changed, otherwhise the root does not change).

* Switch rpc to use same format as ext: more future proof.

* use root from child info for trie backend essence.

* Breaking long lines.

* Update doc and clean pr a bit.

* fix error type

* Restore removed doc on merge and update sr-io doc.

* Switch child storage api to use directly unique id, if managed id
where to be put in place, the api will change at this time.

* Clean deprecated host interface from child.

* Removing assertion on child info (can fail depending on root
memoization).

* merging child info in the overlay when possible.

* child iteration by prefix using child_info.

* Using ChainInfo in frame support. ChainInfo gets redesign to avoid
buffers allocation on every calls.

* Add length of root to the data of child info.

* comments

* Encode compact.

* Remove child info with root.

* Fix try_update condition.

* Comment Ext child root caching.

* Replace tuples by struct with field

* remove StorageTuple alias.

* Fix doc tests, and remove StorageOverlay and ChildStorageOverlay
aliases.

substrate/client/db/src/storage_cache.rs

@@ -23,6 +23,7 @@ use linked_hash_map::{LinkedHashMap, Entry};
 use hash_db::Hasher;
 use sp_runtime::traits::{Block as BlockT, Header};
 use primitives::hexdisplay::HexDisplay;
+use primitives::storage::ChildInfo;
 use state_machine::{backend::Backend as StateBackend, TrieBackend};
 use log::trace;
 use client_api::backend::{StorageCollection, ChildStorageCollection};
@@ -516,7 +517,12 @@ impl<H: Hasher, S: StateBackend<H>, B: BlockT> StateBackend<H> for CachingState<
 		Ok(hash)
 	}
 
-	fn child_storage(&self, storage_key: &[u8], key: &[u8]) -> Result<Option<Vec<u8>>, Self::Error> {
+	fn child_storage(
+		&self,
+		storage_key: &[u8],
+		child_info: ChildInfo,
+		key: &[u8],
+	) -> Result<Option<Vec<u8>>, Self::Error> {
 		let key = (storage_key.to_vec(), key.to_vec());
 		let local_cache = self.cache.local_cache.upgradable_read();
 		if let Some(entry) = local_cache.child_storage.get(&key).cloned() {
@@ -531,7 +537,7 @@ impl<H: Hasher, S: StateBackend<H>, B: BlockT> StateBackend<H> for CachingState<
 			}
 		}
 		trace!("Cache miss: {:?}", key);
-		let value = self.state.child_storage(storage_key, &key.1[..])?;
+		let value = self.state.child_storage(storage_key, child_info, &key.1[..])?;
 		RwLockUpgradableReadGuard::upgrade(local_cache).child_storage.insert(key, value.clone());
 		Ok(value)
 	}
@@ -540,20 +546,35 @@ impl<H: Hasher, S: StateBackend<H>, B: BlockT> StateBackend<H> for CachingState<
 		Ok(self.storage(key)?.is_some())
 	}
 
-	fn exists_child_storage(&self, storage_key: &[u8], key: &[u8]) -> Result<bool, Self::Error> {
-		self.state.exists_child_storage(storage_key, key)
+	fn exists_child_storage(
+		&self,
+		storage_key: &[u8],
+		child_info: ChildInfo,
+		key: &[u8],
+	) -> Result<bool, Self::Error> {
+		self.state.exists_child_storage(storage_key, child_info, key)
+	}
+
+	fn for_keys_in_child_storage<F: FnMut(&[u8])>(
+		&self,
+		storage_key: &[u8],
+		child_info: ChildInfo,
+		f: F,
+	) {
+		self.state.for_keys_in_child_storage(storage_key, child_info, f)
 	}
 
 	fn next_storage_key(&self, key: &[u8]) -> Result<Option<Vec<u8>>, Self::Error> {
 		self.state.next_storage_key(key)
 	}
 
-	fn next_child_storage_key(&self, storage_key: &[u8], key: &[u8]) -> Result<Option<Vec<u8>>, Self::Error> {
-		self.state.next_child_storage_key(storage_key, key)
-	}
-
-	fn for_keys_in_child_storage<F: FnMut(&[u8])>(&self, storage_key: &[u8], f: F) {
-		self.state.for_keys_in_child_storage(storage_key, f)
+	fn next_child_storage_key(
+		&self,
+		storage_key: &[u8],
+		child_info: ChildInfo,
+		key: &[u8],
+	) -> Result<Option<Vec<u8>>, Self::Error> {
+		self.state.next_child_storage_key(storage_key, child_info, key)
 	}
 
 	fn for_keys_with_prefix<F: FnMut(&[u8])>(&self, prefix: &[u8], f: F) {
@@ -564,8 +585,14 @@ impl<H: Hasher, S: StateBackend<H>, B: BlockT> StateBackend<H> for CachingState<
 		self.state.for_key_values_with_prefix(prefix, f)
 	}
 
-	fn for_child_keys_with_prefix<F: FnMut(&[u8])>(&self, storage_key: &[u8], prefix: &[u8], f: F) {
-		self.state.for_child_keys_with_prefix(storage_key, prefix, f)
+	fn for_child_keys_with_prefix<F: FnMut(&[u8])>(
+		&self,
+		storage_key: &[u8],
+		child_info: ChildInfo,
+		prefix: &[u8],
+		f: F,
+	) {
+		self.state.for_child_keys_with_prefix(storage_key, child_info, prefix, f)
 	}
 
 	fn storage_root<I>(&self, delta: I) -> (H::Out, Self::Transaction)
@@ -576,12 +603,17 @@ impl<H: Hasher, S: StateBackend<H>, B: BlockT> StateBackend<H> for CachingState<
 		self.state.storage_root(delta)
 	}
 
-	fn child_storage_root<I>(&self, storage_key: &[u8], delta: I) -> (H::Out, bool, Self::Transaction)
+	fn child_storage_root<I>(
+		&self,
+		storage_key: &[u8],
+		child_info: ChildInfo,
+		delta: I,
+	) -> (H::Out, bool, Self::Transaction)
 		where
 			I: IntoIterator<Item=(Vec<u8>, Option<Vec<u8>>)>,
 			H::Out: Ord
 	{
-		self.state.child_storage_root(storage_key, delta)
+		self.state.child_storage_root(storage_key, child_info, delta)
 	}
 
 	fn pairs(&self) -> Vec<(Vec<u8>, Vec<u8>)> {
@@ -592,8 +624,13 @@ impl<H: Hasher, S: StateBackend<H>, B: BlockT> StateBackend<H> for CachingState<
 		self.state.keys(prefix)
 	}
 
-	fn child_keys(&self, child_key: &[u8], prefix: &[u8]) -> Vec<Vec<u8>> {
-		self.state.child_keys(child_key, prefix)
+	fn child_keys(
+		&self,
+		storage_key: &[u8],
+		child_info: ChildInfo,
+		prefix: &[u8],
+	) -> Vec<Vec<u8>> {
+		self.state.child_keys(storage_key, child_info, prefix)
 	}
 
 	fn as_trie_backend(&mut self) -> Option<&TrieBackend<Self::TrieBackendStorage, H>> {