Fetching logs by hash in blockchain database (#8463)

* Fetch logs by hash in blockchain database

* Fix tests

* Add unit test for branch block logs fetching

* Add docs that blocks must already be sorted

* Handle branch block cases properly

* typo: empty -> is_empty

* Remove return_empty_if_none by using a closure

* Use BTreeSet to avoid sorting again

* Move is_canon to BlockChain

* typo: pass value by reference

* Use loop and wrap inside blocks to simplify the code

Borrowed from https://github.com/paritytech/parity/pull/8463#discussion_r183453326

* typo: missed a comment

ethcore/src/blockchain/blockchain.rs

@@ -57,6 +57,12 @@ pub trait BlockProvider {
 	/// (though not necessarily a part of the canon chain).
 	fn is_known(&self, hash: &H256) -> bool;
 
+	/// Returns true if the given block is known and in the canon chain.
+	fn is_canon(&self, hash: &H256) -> bool {
+		let is_canon = || Some(hash == &self.block_hash(self.block_number(hash)?)?);
+		is_canon().unwrap_or(false)
+	}
+
 	/// Get the first block of the best part of the chain.
 	/// Return `None` if there is no gap and the first block is the genesis.
 	/// Any queries of blocks which precede this one are not guaranteed to
@@ -153,7 +159,7 @@ pub trait BlockProvider {
 	fn blocks_with_bloom(&self, bloom: &Bloom, from_block: BlockNumber, to_block: BlockNumber) -> Vec<BlockNumber>;
 
 	/// Returns logs matching given filter.
-	fn logs<F>(&self, blocks: Vec<BlockNumber>, matches: F, limit: Option<usize>) -> Vec<LocalizedLogEntry>
+	fn logs<F>(&self, blocks: Vec<H256>, matches: F, limit: Option<usize>) -> Vec<LocalizedLogEntry>
 		where F: Fn(&LogEntry) -> bool + Send + Sync, Self: Sized;
 }
 
@@ -360,16 +366,18 @@ impl BlockProvider for BlockChain {
 			.collect()
 	}
 
-	fn logs<F>(&self, mut blocks: Vec<BlockNumber>, matches: F, limit: Option<usize>) -> Vec<LocalizedLogEntry>
+	/// Returns logs matching given filter. The order of logs returned will be the same as the order of the blocks
+	/// provided. And it's the callers responsibility to sort blocks provided in advance.
+	fn logs<F>(&self, mut blocks: Vec<H256>, matches: F, limit: Option<usize>) -> Vec<LocalizedLogEntry>
 		where F: Fn(&LogEntry) -> bool + Send + Sync, Self: Sized {
 		// sort in reverse order
-		blocks.sort_by(|a, b| b.cmp(a));
+		blocks.reverse();
 
 		let mut logs = blocks
 			.chunks(128)
 			.flat_map(move |blocks_chunk| {
 				blocks_chunk.into_par_iter()
-					.filter_map(|number| self.block_hash(*number).map(|hash| (*number, hash)))
+					.filter_map(|hash| self.block_number(&hash).map(|r| (r, hash)))
 					.filter_map(|(number, hash)| self.block_receipts(&hash).map(|r| (number, hash, r.receipts)))
 					.filter_map(|(number, hash, receipts)| self.block_body(&hash).map(|ref b| (number, hash, receipts, b.transaction_hashes())))
 					.flat_map(|(number, hash, mut receipts, mut hashes)| {
@@ -396,7 +404,7 @@ impl BlockProvider for BlockChain {
 									.enumerate()
 									.map(move |(i, log)| LocalizedLogEntry {
 										entry: log,
-										block_hash: hash,
+										block_hash: *hash,
 										block_number: number,
 										transaction_hash: tx_hash,
 										// iterating in reverse order
@@ -1957,17 +1965,33 @@ mod tests {
 			value: 103.into(),
 			data: "601080600c6000396000f3006000355415600957005b60203560003555".from_hex().unwrap(),
 		}.sign(&secret(), None);
+		let t4 = Transaction {
+			nonce: 0.into(),
+			gas_price: 0.into(),
+			gas: 100_000.into(),
+			action: Action::Create,
+			value: 104.into(),
+			data: "601080600c6000396000f3006000355415600957005b60203560003555".from_hex().unwrap(),
+		}.sign(&secret(), None);
 		let tx_hash1 = t1.hash();
 		let tx_hash2 = t2.hash();
 		let tx_hash3 = t3.hash();
+		let tx_hash4 = t4.hash();
 
 		let genesis = BlockBuilder::genesis();
 		let b1 = genesis.add_block_with_transactions(vec![t1, t2]);
 		let b2 = b1.add_block_with_transactions(iter::once(t3));
+		let b3 = genesis.add_block_with(|| BlockOptions {
+			transactions: vec![t4.clone()],
+			difficulty: U256::from(9),
+			..Default::default()
+		}); // Branch block
 		let b1_hash = b1.last().hash();
 		let b1_number = b1.last().number();
 		let b2_hash = b2.last().hash();
 		let b2_number = b2.last().number();
+		let b3_hash = b3.last().hash();
+		let b3_number = b3.last().number();
 
 		let db = new_db();
 		let bc = new_chain(&genesis.last().encoded(), db.clone());
@@ -1998,10 +2022,21 @@ mod tests {
 				],
 			}
 		]);
+		insert_block(&db, &bc, &b3.last().encoded(), vec![
+			Receipt {
+				outcome: TransactionOutcome::StateRoot(H256::default()),
+				gas_used: 10_000.into(),
+				log_bloom: Default::default(),
+				logs: vec![
+					LogEntry { address: Default::default(), topics: vec![], data: vec![5], },
+				],
+			}
+		]);
 
 		// when
-		let logs1 = bc.logs(vec![1, 2], |_| true, None);
-		let logs2 = bc.logs(vec![1, 2], |_| true, Some(1));
+		let logs1 = bc.logs(vec![b1_hash, b2_hash], |_| true, None);
+		let logs2 = bc.logs(vec![b1_hash, b2_hash], |_| true, Some(1));
+		let logs3 = bc.logs(vec![b3_hash], |_| true, None);
 
 		// then
 		assert_eq!(logs1, vec![
@@ -2053,6 +2088,17 @@ mod tests {
 				log_index: 0,
 			}
 		]);
+		assert_eq!(logs3, vec![
+			LocalizedLogEntry {
+				entry: LogEntry { address: Default::default(), topics: vec![], data: vec![5] },
+				block_hash: b3_hash,
+				block_number: b3_number,
+				transaction_hash: tx_hash4,
+				transaction_index: 0,
+				transaction_log_index: 0,
+				log_index: 0,
+			}
+		]);
 	}
 
 	#[test]

ethcore/src/client/client.rs

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::collections::{HashSet, HashMap, BTreeMap, VecDeque};
+use std::collections::{HashSet, HashMap, BTreeMap, BTreeSet, VecDeque};
 use std::str::FromStr;
 use std::sync::{Arc, Weak};
 use std::sync::atomic::{AtomicUsize, AtomicBool, Ordering as AtomicOrdering};
@@ -1666,23 +1666,82 @@ impl BlockChainClient for Client {
 	}
 
 	fn logs(&self, filter: Filter) -> Vec<LocalizedLogEntry> {
-		let (from, to) = match (self.block_number_ref(&filter.from_block), self.block_number_ref(&filter.to_block)) {
-			(Some(from), Some(to)) => (from, to),
-			_ => return Vec::new(),
+		// Wrap the logic inside a closure so that we can take advantage of question mark syntax.
+		let fetch_logs = || {
+			let chain = self.chain.read();
+
+			// First, check whether `filter.from_block` and `filter.to_block` is on the canon chain. If so, we can use the
+			// optimized version.
+			let is_canon = |id| {
+				match id {
+					// If it is referred by number, then it is always on the canon chain.
+					&BlockId::Earliest | &BlockId::Latest | &BlockId::Number(_) => true,
+					// If it is referred by hash, we see whether a hash -> number -> hash conversion gives us the same
+					// result.
+					&BlockId::Hash(ref hash) => chain.is_canon(hash),
+				}
 			};
 
-		let chain = self.chain.read();
-		let blocks = filter.bloom_possibilities().iter()
-			.map(move |bloom| {
+			let blocks = if is_canon(&filter.from_block) && is_canon(&filter.to_block) {
+				// If we are on the canon chain, use bloom filter to fetch required hashes.
+				let from = self.block_number_ref(&filter.from_block)?;
+				let to = self.block_number_ref(&filter.to_block)?;
+
+				filter.bloom_possibilities().iter()
+					.map(|bloom| {
 						chain.blocks_with_bloom(bloom, from, to)
 					})
 					.flat_map(|m| m)
 					// remove duplicate elements
-			.collect::<HashSet<u64>>()
+					.collect::<BTreeSet<u64>>()
 					.into_iter()
-			.collect::<Vec<u64>>();
+					.filter_map(|n| chain.block_hash(n))
+					.collect::<Vec<H256>>()
 
-		self.chain.read().logs(blocks, |entry| filter.matches(entry), filter.limit)
+			} else {
+				// Otherwise, we use a slower version that finds a link between from_block and to_block.
+				let from_hash = Self::block_hash(&chain, filter.from_block)?;
+				let from_number = chain.block_number(&from_hash)?;
+				let to_hash = Self::block_hash(&chain, filter.from_block)?;
+
+				let blooms = filter.bloom_possibilities();
+				let bloom_match = |header: &encoded::Header| {
+					blooms.iter().any(|bloom| header.log_bloom().contains_bloom(bloom))
+				};
+
+				let (blocks, last_hash) = {
+					let mut blocks = Vec::new();
+					let mut current_hash = to_hash;
+
+					loop {
+						let header = chain.block_header_data(&current_hash)?;
+						if bloom_match(&header) {
+							blocks.push(current_hash);
+						}
+
+						// Stop if `from` block is reached.
+						if header.number() <= from_number {
+							break;
+						}
+						current_hash = header.parent_hash();
+					}
+
+					blocks.reverse();
+					(blocks, current_hash)
+				};
+
+				// Check if we've actually reached the expected `from` block.
+				if last_hash != from_hash || blocks.is_empty() {
+					return None;
+				}
+
+				blocks
+			};
+
+			Some(self.chain.read().logs(blocks, |entry| filter.matches(entry), filter.limit))
+		};
+
+		fetch_logs().unwrap_or_default()
 	}
 
 	fn filter_traces(&self, filter: TraceFilter) -> Option<Vec<LocalizedTrace>> {

ethcore/src/verification/verification.rs

@@ -458,7 +458,7 @@ mod tests {
 			unimplemented!()
 		}
 
-		fn logs<F>(&self, _blocks: Vec<BlockNumber>, _matches: F, _limit: Option<usize>) -> Vec<LocalizedLogEntry>
+		fn logs<F>(&self, _blocks: Vec<H256>, _matches: F, _limit: Option<usize>) -> Vec<LocalizedLogEntry>
 			where F: Fn(&LogEntry) -> bool, Self: Sized {
 			unimplemented!()
 		}