DB v1->v2 migration (#3044)

* wip

* exhaustive match

* wip

* cleanup docs and move migration fns to chain itself

chain/src/chain.rs

@@ -189,7 +189,7 @@ impl Chain {
 		)?;
 		Chain::log_heads(&store)?;
 
-		Ok(Chain {
+		let chain = Chain {
 			db_root,
 			store,
 			adapter,
@@ -201,7 +201,18 @@ impl Chain {
 			verifier_cache,
 			archive_mode,
 			genesis: genesis.header.clone(),
-		})
+		};
+
+		// DB migrations to be run prior to the chain being used.
+		{
+			// Migrate full blocks to protocol version v2.
+			chain.migrate_db_v1_v2()?;
+
+			// Rebuild height_for_pos index.
+			chain.rebuild_height_for_pos()?;
+		}
+
+		Ok(chain)
 	}
 
 	/// Return our shared header MMR handle.
@@ -1245,9 +1256,22 @@ impl Chain {
 		self.header_pmmr.read().get_header_hash_by_height(height)
 	}
 
+	/// Migrate our local db from v1 to v2.
+	/// This covers blocks which themselves contain transactions.
+	/// Transaction kernels changed in v2 due to "variable size kernels".
+	fn migrate_db_v1_v2(&self) -> Result<(), Error> {
+		let store_v1 = self.store.with_version(ProtocolVersion(1));
+		let batch = store_v1.batch()?;
+		for (_, block) in batch.blocks_iter()? {
+			batch.migrate_block(&block, ProtocolVersion(2))?;
+		}
+		batch.commit()?;
+		Ok(())
+	}
+
 	/// Migrate the index 'commitment -> output_pos' to index 'commitment -> (output_pos, block_height)'
 	/// Note: should only be called when Node start-up, for database migration from the old version.
-	pub fn rebuild_height_for_pos(&self) -> Result<(), Error> {
+	fn rebuild_height_for_pos(&self) -> Result<(), Error> {
 		let header_pmmr = self.header_pmmr.read();
 		let txhashset = self.txhashset.read();
 		let mut outputs_pos = txhashset.get_all_output_pos()?;

chain/src/store.rs

@@ -18,6 +18,7 @@ use crate::core::consensus::HeaderInfo;
 use crate::core::core::hash::{Hash, Hashed};
 use crate::core::core::{Block, BlockHeader, BlockSums};
 use crate::core::pow::Difficulty;
+use crate::core::ser::ProtocolVersion;
 use crate::types::Tip;
 use crate::util::secp::pedersen::Commitment;
 use croaring::Bitmap;
@@ -49,6 +50,17 @@ impl ChainStore {
 		let db = store::Store::new(db_root, None, Some(STORE_SUBPATH.clone()), None)?;
 		Ok(ChainStore { db })
 	}
+
+	/// Create a new instance of the chain store based on this instance
+	/// but with the provided protocol version. This is used when migrating
+	/// data in the db to a different protocol version, reading using one version and
+	/// writing back to the db with a different version.
+	pub fn with_version(&self, version: ProtocolVersion) -> ChainStore {
+		let db_with_version = self.db.with_version(version);
+		ChainStore {
+			db: db_with_version,
+		}
+	}
 }
 
 impl ChainStore {
@@ -258,6 +270,17 @@ impl<'a> Batch<'a> {
 		Ok(())
 	}
 
+	/// Migrate a block stored in the db by serializing it using the provided protocol version.
+	/// Block may have been read using a previous protocol version but we do not actually care.
+	pub fn migrate_block(&self, b: &Block, version: ProtocolVersion) -> Result<(), Error> {
+		self.db.put_ser_with_version(
+			&to_key(BLOCK_PREFIX, &mut b.hash().to_vec())[..],
+			b,
+			version,
+		)?;
+		Ok(())
+	}
+
 	/// Delete a full block. Does not delete any record associated with a block
 	/// header.
 	pub fn delete_block(&self, bh: &Hash) -> Result<(), Error> {