Merge pull request 'Refactor how things are migrated' (#461) from format-migration into main

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/461

15 files changed, 506 insertions, 681 deletions

diff --git a/src/model/Cargo.toml b/src/model/Cargo.toml
index 3d3fb693..323c2d64 100644
--- a/src/model/Cargo.toml
+++ b/src/model/Cargo.toml
@@ -30,7 +30,6 @@ tracing = "0.1.30"
 rand = "0.8"
 zstd = { version = "0.9", default-features = false }
 
-rmp-serde = "0.15"
 serde = { version = "1.0", default-features = false, features = ["derive", "rc"] }
 serde_bytes = "0.11"
 
diff --git a/src/model/bucket_alias_table.rs b/src/model/bucket_alias_table.rs
index fcd1536e..54d7fbad 100644
--- a/src/model/bucket_alias_table.rs
+++ b/src/model/bucket_alias_table.rs
@@ -1,18 +1,26 @@
-use serde::{Deserialize, Serialize};
-
 use garage_util::data::*;
 
 use garage_table::crdt::*;
 use garage_table::*;
 
-/// The bucket alias table holds the names given to buckets
-/// in the global namespace.
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct BucketAlias {
-	name: String,
-	pub state: crdt::Lww<Option<Uuid>>,
+mod v08 {
+	use garage_util::crdt;
+	use garage_util::data::Uuid;
+	use serde::{Deserialize, Serialize};
+
+	/// The bucket alias table holds the names given to buckets
+	/// in the global namespace.
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct BucketAlias {
+		pub(super) name: String,
+		pub state: crdt::Lww<Option<Uuid>>,
+	}
+
+	impl garage_util::migrate::InitialFormat for BucketAlias {}
 }
 
+pub use v08::*;
+
 impl BucketAlias {
 	pub fn new(name: String, ts: u64, bucket_id: Option<Uuid>) -> Option<Self> {
 		if !is_valid_bucket_name(&name) {
diff --git a/src/model/bucket_table.rs b/src/model/bucket_table.rs
index 7be42702..ac163736 100644
--- a/src/model/bucket_table.rs
+++ b/src/model/bucket_table.rs
@@ -1,5 +1,3 @@
-use serde::{Deserialize, Serialize};
-
 use garage_table::crdt::*;
 use garage_table::*;
 use garage_util::data::*;
@@ -7,72 +5,83 @@ use garage_util::time::*;
 
 use crate::permission::BucketKeyPerm;
 
-/// A bucket is a collection of objects
-///
-/// Its parameters are not directly accessible as:
-///  - It must be possible to merge paramaters, hence the use of a LWW CRDT.
-///  - A bucket has 2 states, Present or Deleted and parameters make sense only if present.
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct Bucket {
-	/// ID of the bucket
-	pub id: Uuid,
-	/// State, and configuration if not deleted, of the bucket
-	pub state: crdt::Deletable<BucketParams>,
-}
+mod v08 {
+	use crate::permission::BucketKeyPerm;
+	use garage_util::crdt;
+	use garage_util::data::Uuid;
+	use serde::{Deserialize, Serialize};
+
+	/// A bucket is a collection of objects
+	///
+	/// Its parameters are not directly accessible as:
+	///  - It must be possible to merge paramaters, hence the use of a LWW CRDT.
+	///  - A bucket has 2 states, Present or Deleted and parameters make sense only if present.
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct Bucket {
+		/// ID of the bucket
+		pub id: Uuid,
+		/// State, and configuration if not deleted, of the bucket
+		pub state: crdt::Deletable<BucketParams>,
+	}
 
-/// Configuration for a bucket
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct BucketParams {
-	/// Bucket's creation date
-	pub creation_date: u64,
-	/// Map of key with access to the bucket, and what kind of access they give
-	pub authorized_keys: crdt::Map<String, BucketKeyPerm>,
-
-	/// Map of aliases that are or have been given to this bucket
-	/// in the global namespace
-	/// (not authoritative: this is just used as an indication to
-	/// map back to aliases when doing ListBuckets)
-	pub aliases: crdt::LwwMap<String, bool>,
-	/// Map of aliases that are or have been given to this bucket
-	/// in namespaces local to keys
-	/// key = (access key id, alias name)
-	pub local_aliases: crdt::LwwMap<(String, String), bool>,
-
-	/// Whether this bucket is allowed for website access
-	/// (under all of its global alias names),
-	/// and if so, the website configuration XML document
-	pub website_config: crdt::Lww<Option<WebsiteConfig>>,
-	/// CORS rules
-	pub cors_config: crdt::Lww<Option<Vec<CorsRule>>>,
-	/// Bucket quotas
-	#[serde(default)]
-	pub quotas: crdt::Lww<BucketQuotas>,
-}
+	/// Configuration for a bucket
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct BucketParams {
+		/// Bucket's creation date
+		pub creation_date: u64,
+		/// Map of key with access to the bucket, and what kind of access they give
+		pub authorized_keys: crdt::Map<String, BucketKeyPerm>,
+
+		/// Map of aliases that are or have been given to this bucket
+		/// in the global namespace
+		/// (not authoritative: this is just used as an indication to
+		/// map back to aliases when doing ListBuckets)
+		pub aliases: crdt::LwwMap<String, bool>,
+		/// Map of aliases that are or have been given to this bucket
+		/// in namespaces local to keys
+		/// key = (access key id, alias name)
+		pub local_aliases: crdt::LwwMap<(String, String), bool>,
+
+		/// Whether this bucket is allowed for website access
+		/// (under all of its global alias names),
+		/// and if so, the website configuration XML document
+		pub website_config: crdt::Lww<Option<WebsiteConfig>>,
+		/// CORS rules
+		pub cors_config: crdt::Lww<Option<Vec<CorsRule>>>,
+		/// Bucket quotas
+		#[serde(default)]
+		pub quotas: crdt::Lww<BucketQuotas>,
+	}
 
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct WebsiteConfig {
-	pub index_document: String,
-	pub error_document: Option<String>,
-}
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct WebsiteConfig {
+		pub index_document: String,
+		pub error_document: Option<String>,
+	}
 
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct CorsRule {
-	pub id: Option<String>,
-	pub max_age_seconds: Option<u64>,
-	pub allow_origins: Vec<String>,
-	pub allow_methods: Vec<String>,
-	pub allow_headers: Vec<String>,
-	pub expose_headers: Vec<String>,
-}
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct CorsRule {
+		pub id: Option<String>,
+		pub max_age_seconds: Option<u64>,
+		pub allow_origins: Vec<String>,
+		pub allow_methods: Vec<String>,
+		pub allow_headers: Vec<String>,
+		pub expose_headers: Vec<String>,
+	}
 
-#[derive(Default, PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub struct BucketQuotas {
-	/// Maximum size in bytes (bucket size = sum of sizes of objects in the bucket)
-	pub max_size: Option<u64>,
-	/// Maximum number of non-deleted objects in the bucket
-	pub max_objects: Option<u64>,
+	#[derive(Default, PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
+	pub struct BucketQuotas {
+		/// Maximum size in bytes (bucket size = sum of sizes of objects in the bucket)
+		pub max_size: Option<u64>,
+		/// Maximum number of non-deleted objects in the bucket
+		pub max_objects: Option<u64>,
+	}
+
+	impl garage_util::migrate::InitialFormat for Bucket {}
 }
 
+pub use v08::*;
+
 impl AutoCrdt for BucketQuotas {
 	const WARN_IF_DIFFERENT: bool = true;
 }
diff --git a/src/model/index_counter.rs b/src/model/index_counter.rs
index 6303ea3e..35d6596d 100644
--- a/src/model/index_counter.rs
+++ b/src/model/index_counter.rs
@@ -12,6 +12,7 @@ use garage_rpc::system::System;
 use garage_util::background::BackgroundRunner;
 use garage_util::data::*;
 use garage_util::error::*;
+use garage_util::migrate::Migrate;
 use garage_util::time::*;
 
 use garage_table::crdt::*;
@@ -29,14 +30,44 @@ pub trait CountedItem: Clone + PartialEq + Send + Sync + 'static {
 	fn counts(&self) -> Vec<(&'static str, i64)>;
 }
 
-/// A counter entry in the global table
-#[derive(Clone, PartialEq, Debug, Serialize, Deserialize)]
-pub struct CounterEntry<T: CountedItem> {
-	pub pk: T::CP,
-	pub sk: T::CS,
-	pub values: BTreeMap<String, CounterValue>,
+mod v08 {
+	use super::CountedItem;
+	use garage_util::data::Uuid;
+	use serde::{Deserialize, Serialize};
+	use std::collections::BTreeMap;
+
+	// ---- Global part (the table everyone queries) ----
+
+	/// A counter entry in the global table
+	#[derive(Clone, PartialEq, Debug, Serialize, Deserialize)]
+	pub struct CounterEntry<T: CountedItem> {
+		pub pk: T::CP,
+		pub sk: T::CS,
+		pub values: BTreeMap<String, CounterValue>,
+	}
+
+	/// A counter entry in the global table
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct CounterValue {
+		pub node_values: BTreeMap<Uuid, (u64, i64)>,
+	}
+
+	impl<T: CountedItem> garage_util::migrate::InitialFormat for CounterEntry<T> {}
+
+	// ---- Local part (the counter we maintain transactionnaly on each node) ----
+
+	#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+	pub(super) struct LocalCounterEntry<T: CountedItem> {
+		pub(super) pk: T::CP,
+		pub(super) sk: T::CS,
+		pub(super) values: BTreeMap<String, (u64, i64)>,
+	}
+
+	impl<T: CountedItem> garage_util::migrate::InitialFormat for LocalCounterEntry<T> {}
 }
 
+pub use v08::*;
+
 impl<T: CountedItem> Entry<T::CP, T::CS> for CounterEntry<T> {
 	fn partition_key(&self) -> &T::CP {
 		&self.pk
@@ -78,12 +109,6 @@ impl<T: CountedItem> CounterEntry<T> {
 	}
 }
 
-/// A counter entry in the global table
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct CounterValue {
-	pub node_values: BTreeMap<Uuid, (u64, i64)>,
-}
-
 impl<T: CountedItem> Crdt for CounterEntry<T> {
 	fn merge(&mut self, other: &Self) {
 		for (name, e2) in other.values.iter() {
@@ -195,11 +220,9 @@ impl<T: CountedItem> IndexCounter<T> {
 		let tree_key = self.table.data.tree_key(pk, sk);
 
 		let mut entry = match tx.get(&self.local_counter, &tree_key[..])? {
-			Some(old_bytes) => {
-				rmp_serde::decode::from_read_ref::<_, LocalCounterEntry<T>>(&old_bytes)
-					.map_err(Error::RmpDecode)
-					.map_err(db::TxError::Abort)?
-			}
+			Some(old_bytes) => LocalCounterEntry::<T>::decode(&old_bytes)
+				.ok_or_message("Cannot decode local counter entry")
+				.map_err(db::TxError::Abort)?,
 			None => LocalCounterEntry {
 				pk: pk.clone(),
 				sk: sk.clone(),
@@ -214,7 +237,8 @@ impl<T: CountedItem> IndexCounter<T> {
 			ent.1 += *inc;
 		}
 
-		let new_entry_bytes = rmp_to_vec_all_named(&entry)
+		let new_entry_bytes = entry
+			.encode()
 			.map_err(Error::RmpEncode)
 			.map_err(db::TxError::Abort)?;
 		tx.insert(&self.local_counter, &tree_key[..], new_entry_bytes)?;
@@ -255,15 +279,15 @@ impl<T: CountedItem> IndexCounter<T> {
 
 			info!("zeroing old counters... ({})", hex::encode(&batch[0].0));
 			for (local_counter_k, local_counter) in batch {
-				let mut local_counter =
-					rmp_serde::decode::from_read_ref::<_, LocalCounterEntry<T>>(&local_counter)?;
+				let mut local_counter = LocalCounterEntry::<T>::decode(&local_counter)
+					.ok_or_message("Cannot decode local counter entry")?;
 
 				for (_, tv) in local_counter.values.iter_mut() {
 					tv.0 = std::cmp::max(tv.0 + 1, now);
 					tv.1 = 0;
 				}
 
-				let local_counter_bytes = rmp_to_vec_all_named(&local_counter)?;
+				let local_counter_bytes = local_counter.encode()?;
 				self.local_counter
 					.insert(&local_counter_k, &local_counter_bytes)?;
 
@@ -311,9 +335,8 @@ impl<T: CountedItem> IndexCounter<T> {
 				let local_counter_key = self.table.data.tree_key(pk, sk);
 				let mut local_counter = match self.local_counter.get(&local_counter_key)? {
 					Some(old_bytes) => {
-						let ent = rmp_serde::decode::from_read_ref::<_, LocalCounterEntry<T>>(
-							&old_bytes,
-						)?;
+						let ent = LocalCounterEntry::<T>::decode(&old_bytes)
+							.ok_or_message("Cannot decode local counter entry")?;
 						assert!(ent.pk == *pk);
 						assert!(ent.sk == *sk);
 						ent
@@ -330,7 +353,7 @@ impl<T: CountedItem> IndexCounter<T> {
 					tv.1 += v;
 				}
 
-				let local_counter_bytes = rmp_to_vec_all_named(&local_counter)?;
+				let local_counter_bytes = local_counter.encode()?;
 				self.local_counter
 					.insert(&local_counter_key, local_counter_bytes)?;
 
@@ -350,13 +373,6 @@ impl<T: CountedItem> IndexCounter<T> {
 
 // ----
 
-#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
-struct LocalCounterEntry<T: CountedItem> {
-	pk: T::CP,
-	sk: T::CS,
-	values: BTreeMap<String, (u64, i64)>,
-}
-
 impl<T: CountedItem> LocalCounterEntry<T> {
 	fn into_counter_entry(self, this_node: Uuid) -> CounterEntry<T> {
 		CounterEntry {
diff --git a/src/model/k2v/item_table.rs b/src/model/k2v/item_table.rs
index 7860cb17..ce3e4129 100644
--- a/src/model/k2v/item_table.rs
+++ b/src/model/k2v/item_table.rs
@@ -1,7 +1,8 @@
-use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::sync::Arc;
 
+use serde::{Deserialize, Serialize};
+
 use garage_db as db;
 use garage_util::data::*;
 
@@ -17,32 +18,43 @@ pub const CONFLICTS: &str = "conflicts";
 pub const VALUES: &str = "values";
 pub const BYTES: &str = "bytes";
 
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct K2VItem {
-	pub partition: K2VItemPartition,
-	pub sort_key: String,
+mod v08 {
+	use crate::k2v::causality::K2VNodeId;
+	use garage_util::data::Uuid;
+	use serde::{Deserialize, Serialize};
+	use std::collections::BTreeMap;
 
-	items: BTreeMap<K2VNodeId, DvvsEntry>,
-}
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct K2VItem {
+		pub partition: K2VItemPartition,
+		pub sort_key: String,
 
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize, Hash)]
-pub struct K2VItemPartition {
-	pub bucket_id: Uuid,
-	pub partition_key: String,
-}
+		pub(super) items: BTreeMap<K2VNodeId, DvvsEntry>,
+	}
 
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-struct DvvsEntry {
-	t_discard: u64,
-	values: Vec<(u64, DvvsValue)>,
-}
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize, Hash)]
+	pub struct K2VItemPartition {
+		pub bucket_id: Uuid,
+		pub partition_key: String,
+	}
+
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct DvvsEntry {
+		pub(super) t_discard: u64,
+		pub(super) values: Vec<(u64, DvvsValue)>,
+	}
 
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub enum DvvsValue {
-	Value(#[serde(with = "serde_bytes")] Vec<u8>),
-	Deleted,
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub enum DvvsValue {
+		Value(#[serde(with = "serde_bytes")] Vec<u8>),
+		Deleted,
+	}
+
+	impl garage_util::migrate::InitialFormat for K2VItem {}
 }
 
+pub use v08::*;
+
 impl K2VItem {
 	/// Creates a new K2VItem when no previous entry existed in the db
 	pub fn new(bucket_id: Uuid, partition_key: String, sort_key: String) -> Self {
diff --git a/src/model/key_table.rs b/src/model/key_table.rs
index 9d2fc783..bb5334a3 100644
--- a/src/model/key_table.rs
+++ b/src/model/key_table.rs
@@ -1,45 +1,121 @@
 use serde::{Deserialize, Serialize};
 
-use garage_table::crdt::*;
-use garage_table::*;
+use garage_util::crdt::{self, Crdt};
 use garage_util::data::*;
 
+use garage_table::{DeletedFilter, EmptyKey, Entry, TableSchema};
+
 use crate::permission::BucketKeyPerm;
 
-use crate::prev::v051::key_table as old;
+pub(crate) mod v05 {
+	use garage_util::crdt;
+	use serde::{Deserialize, Serialize};
 
-/// An api key
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct Key {
-	/// The id of the key (immutable), used as partition key
-	pub key_id: String,
+	/// An api key
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct Key {
+		/// The id of the key (immutable), used as partition key
+		pub key_id: String,
 
-	/// Internal state of the key
-	pub state: crdt::Deletable<KeyParams>,
-}
+		/// The secret_key associated
+		pub secret_key: String,
 
-/// Configuration for a key
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct KeyParams {
-	/// The secret_key associated (immutable)
-	pub secret_key: String,
+		/// Name for the key
+		pub name: crdt::Lww<String>,
 
-	/// Name for the key
-	pub name: crdt::Lww<String>,
+		/// Is the key deleted
+		pub deleted: crdt::Bool,
+
+		/// Buckets in which the key is authorized. Empty if `Key` is deleted
+		// CRDT interaction: deleted implies authorized_buckets is empty
+		pub authorized_buckets: crdt::LwwMap<String, PermissionSet>,
+	}
 
-	/// Flag to allow users having this key to create buckets
-	pub allow_create_bucket: crdt::Lww<bool>,
+	/// Permission given to a key in a bucket
+	#[derive(PartialOrd, Ord, PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct PermissionSet {
+		/// The key can be used to read the bucket
+		pub allow_read: bool,
+		/// The key can be used to write in the bucket
+		pub allow_write: bool,
+	}
+
+	impl crdt::AutoCrdt for PermissionSet {
+		const WARN_IF_DIFFERENT: bool = true;
+	}
 
-	/// If the key is present: it gives some permissions,
-	/// a map of bucket IDs (uuids) to permissions.
-	/// Otherwise no permissions are granted to key
-	pub authorized_buckets: crdt::Map<Uuid, BucketKeyPerm>,
+	impl garage_util::migrate::InitialFormat for Key {}
+}
 
-	/// A key can have a local view of buckets names it is
-	/// the only one to see, this is the namespace for these aliases
-	pub local_aliases: crdt::LwwMap<String, Option<Uuid>>,
+mod v08 {
+	use super::v05;
+	use crate::permission::BucketKeyPerm;
+	use garage_util::crdt;
+	use garage_util::data::Uuid;
+	use serde::{Deserialize, Serialize};
+
+	/// An api key
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct Key {
+		/// The id of the key (immutable), used as partition key
+		pub key_id: String,
+
+		/// Internal state of the key
+		pub state: crdt::Deletable<KeyParams>,
+	}
+
+	/// Configuration for a key
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct KeyParams {
+		/// The secret_key associated (immutable)
+		pub secret_key: String,
+
+		/// Name for the key
+		pub name: crdt::Lww<String>,
+
+		/// Flag to allow users having this key to create buckets
+		pub allow_create_bucket: crdt::Lww<bool>,
+
+		/// If the key is present: it gives some permissions,
+		/// a map of bucket IDs (uuids) to permissions.
+		/// Otherwise no permissions are granted to key
+		pub authorized_buckets: crdt::Map<Uuid, BucketKeyPerm>,
+
+		/// A key can have a local view of buckets names it is
+		/// the only one to see, this is the namespace for these aliases
+		pub local_aliases: crdt::LwwMap<String, Option<Uuid>>,
+	}
+
+	impl garage_util::migrate::Migrate for Key {
+		type Previous = v05::Key;
+
+		fn migrate(old_k: v05::Key) -> Key {
+			let name = crdt::Lww::raw(old_k.name.timestamp(), old_k.name.get().clone());
+
+			let state = if old_k.deleted.get() {
+				crdt::Deletable::Deleted
+			} else {
+				// Authorized buckets is ignored here,
+				// migration is performed in specific migration code in
+				// garage/migrate.rs
+				crdt::Deletable::Present(KeyParams {
+					secret_key: old_k.secret_key,
+					name,
+					allow_create_bucket: crdt::Lww::new(false),
+					authorized_buckets: crdt::Map::new(),
+					local_aliases: crdt::LwwMap::new(),
+				})
+			};
+			Key {
+				key_id: old_k.key_id,
+				state,
+			}
+		}
+	}
 }
 
+pub use v08::*;
+
 impl KeyParams {
 	fn new(secret_key: &str, name: &str) -> Self {
 		KeyParams {
@@ -173,28 +249,4 @@ impl TableSchema for KeyTable {
 			}
 		}
 	}
-
-	fn try_migrate(bytes: &[u8]) -> Option<Self::E> {
-		let old_k = rmp_serde::decode::from_read_ref::<_, old::Key>(bytes).ok()?;
-		let name = crdt::Lww::raw(old_k.name.timestamp(), old_k.name.get().clone());
-
-		let state = if old_k.deleted.get() {
-			crdt::Deletable::Deleted
-		} else {
-			// Authorized buckets is ignored here,
-			// migration is performed in specific migration code in
-			// garage/migrate.rs
-			crdt::Deletable::Present(KeyParams {
-				secret_key: old_k.secret_key,
-				name,
-				allow_create_bucket: crdt::Lww::new(false),
-				authorized_buckets: crdt::Map::new(),
-				local_aliases: crdt::LwwMap::new(),
-			})
-		};
-		Some(Key {
-			key_id: old_k.key_id,
-			state,
-		})
-	}
 }
diff --git a/src/model/migrate.rs b/src/model/migrate.rs
index cd6ad26a..6b4c3eed 100644
--- a/src/model/migrate.rs
+++ b/src/model/migrate.rs
@@ -2,6 +2,7 @@ use std::sync::Arc;
 
 use garage_util::crdt::*;
 use garage_util::data::*;
+use garage_util::encode::nonversioned_decode;
 use garage_util::error::Error as GarageError;
 use garage_util::time::*;
 
@@ -28,8 +29,8 @@ impl Migrate {
 		let mut old_buckets = vec![];
 		for res in tree.iter().map_err(GarageError::from)? {
 			let (_k, v) = res.map_err(GarageError::from)?;
-			let bucket = rmp_serde::decode::from_read_ref::<_, old_bucket::Bucket>(&v[..])
-				.map_err(GarageError::from)?;
+			let bucket =
+				nonversioned_decode::<old_bucket::Bucket>(&v[..]).map_err(GarageError::from)?;
 			old_buckets.push(bucket);
 		}
 
diff --git a/src/model/prev/v051/bucket_table.rs b/src/model/prev/v051/bucket_table.rs
index 628a49dd..19893458 100644
--- a/src/model/prev/v051/bucket_table.rs
+++ b/src/model/prev/v051/bucket_table.rs
@@ -3,7 +3,7 @@ use serde::{Deserialize, Serialize};
 use garage_table::crdt::Crdt;
 use garage_table::*;
 
-use super::key_table::PermissionSet;
+use crate::key_table::v05::PermissionSet;
 
 /// A bucket is a collection of objects
 ///
diff --git a/src/model/prev/v051/key_table.rs b/src/model/prev/v051/key_table.rs
deleted file mode 100644
index 37516b1c..00000000
--- a/src/model/prev/v051/key_table.rs
+++ /dev/null
@@ -1,50 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use garage_table::crdt::*;
-use garage_table::*;
-
-/// An api key
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct Key {
-	/// The id of the key (immutable), used as partition key
-	pub key_id: String,
-
-	/// The secret_key associated
-	pub secret_key: String,
-
-	/// Name for the key
-	pub name: crdt::Lww<String>,
-
-	/// Is the key deleted
-	pub deleted: crdt::Bool,
-
-	/// Buckets in which the key is authorized. Empty if `Key` is deleted
-	// CRDT interaction: deleted implies authorized_buckets is empty
-	pub authorized_buckets: crdt::LwwMap<String, PermissionSet>,
-}
-
-/// Permission given to a key in a bucket
-#[derive(PartialOrd, Ord, PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct PermissionSet {
-	/// The key can be used to read the bucket
-	pub allow_read: bool,
-	/// The key can be used to write in the bucket
-	pub allow_write: bool,
-}
-
-impl AutoCrdt for PermissionSet {
-	const WARN_IF_DIFFERENT: bool = true;
-}
-
-impl Crdt for Key {
-	fn merge(&mut self, other: &Self) {
-		self.name.merge(&other.name);
-		self.deleted.merge(&other.deleted);
-
-		if self.deleted.get() {
-			self.authorized_buckets.clear();
-		} else {
-			self.authorized_buckets.merge(&other.authorized_buckets);
-		}
-	}
-}
diff --git a/src/model/prev/v051/mod.rs b/src/model/prev/v051/mod.rs
index 7a954752..8c1335a5 100644
--- a/src/model/prev/v051/mod.rs
+++ b/src/model/prev/v051/mod.rs
@@ -1,4 +1 @@
 pub(crate) mod bucket_table;
-pub(crate) mod key_table;
-pub(crate) mod object_table;
-pub(crate) mod version_table;
diff --git a/src/model/prev/v051/object_table.rs b/src/model/prev/v051/object_table.rs
deleted file mode 100644
index e79e5787..00000000
--- a/src/model/prev/v051/object_table.rs
+++ /dev/null
@@ -1,149 +0,0 @@
-use serde::{Deserialize, Serialize};
-use std::collections::BTreeMap;
-
-use garage_util::data::*;
-
-use garage_table::crdt::*;
-
-/// An object
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct Object {
-	/// The bucket in which the object is stored, used as partition key
-	pub bucket: String,
-
-	/// The key at which the object is stored in its bucket, used as sorting key
-	pub key: String,
-
-	/// The list of currenty stored versions of the object
-	versions: Vec<ObjectVersion>,
-}
-
-impl Object {
-	/// Get a list of currently stored versions of `Object`
-	pub fn versions(&self) -> &[ObjectVersion] {
-		&self.versions[..]
-	}
-}
-
-/// Informations about a version of an object
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct ObjectVersion {
-	/// Id of the version
-	pub uuid: Uuid,
-	/// Timestamp of when the object was created
-	pub timestamp: u64,
-	/// State of the version
-	pub state: ObjectVersionState,
-}
-
-/// State of an object version
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub enum ObjectVersionState {
-	/// The version is being received
-	Uploading(ObjectVersionHeaders),
-	/// The version is fully received
-	Complete(ObjectVersionData),
-	/// The version uploaded containded errors or the upload was explicitly aborted
-	Aborted,
-}
-
-impl Crdt for ObjectVersionState {
-	fn merge(&mut self, other: &Self) {
-		use ObjectVersionState::*;
-		match other {
-			Aborted => {
-				*self = Aborted;
-			}
-			Complete(b) => match self {
-				Aborted => {}
-				Complete(a) => {
-					a.merge(b);
-				}
-				Uploading(_) => {
-					*self = Complete(b.clone());
-				}
-			},
-			Uploading(_) => {}
-		}
-	}
-}
-
-/// Data stored in object version
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub enum ObjectVersionData {
-	/// The object was deleted, this Version is a tombstone to mark it as such
-	DeleteMarker,
-	/// The object is short, it's stored inlined
-	Inline(ObjectVersionMeta, #[serde(with = "serde_bytes")] Vec<u8>),
-	/// The object is not short, Hash of first block is stored here, next segments hashes are
-	/// stored in the version table
-	FirstBlock(ObjectVersionMeta, Hash),
-}
-
-impl AutoCrdt for ObjectVersionData {
-	const WARN_IF_DIFFERENT: bool = true;
-}
-
-/// Metadata about the object version
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub struct ObjectVersionMeta {
-	/// Headers to send to the client
-	pub headers: ObjectVersionHeaders,
-	/// Size of the object
-	pub size: u64,
-	/// etag of the object
-	pub etag: String,
-}
-
-/// Additional headers for an object
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub struct ObjectVersionHeaders {
-	/// Content type of the object
-	pub content_type: String,
-	/// Any other http headers to send
-	pub other: BTreeMap<String, String>,
-}
-
-impl ObjectVersion {
-	fn cmp_key(&self) -> (u64, Uuid) {
-		(self.timestamp, self.uuid)
-	}
-
-	/// Is the object version completely received
-	pub fn is_complete(&self) -> bool {
-		matches!(self.state, ObjectVersionState::Complete(_))
-	}
-}
-
-impl Crdt for Object {
-	fn merge(&mut self, other: &Self) {
-		// Merge versions from other into here
-		for other_v in other.versions.iter() {
-			match self
-				.versions
-				.binary_search_by(|v| v.cmp_key().cmp(&other_v.cmp_key()))
-			{
-				Ok(i) => {
-					self.versions[i].state.merge(&other_v.state);
-				}
-				Err(i) => {
-					self.versions.insert(i, other_v.clone());
-				}
-			}
-		}
-
-		// Remove versions which are obsolete, i.e. those that come
-		// before the last version which .is_complete().
-		let last_complete = self
-			.versions
-			.iter()
-			.enumerate()
-			.rev()
-			.find(|(_, v)| v.is_complete())
-			.map(|(vi, _)| vi);
-
-		if let Some(last_vi) = last_complete {
-			self.versions = self.versions.drain(last_vi..).collect::<Vec<_>>();
-		}
-	}
-}
diff --git a/src/model/prev/v051/version_table.rs b/src/model/prev/v051/version_table.rs
deleted file mode 100644
index c11c62d5..00000000
--- a/src/model/prev/v051/version_table.rs
+++ /dev/null
@@ -1,79 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use garage_util::data::*;
-
-use garage_table::crdt::*;
-use garage_table::*;
-
-/// A version of an object
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct Version {
-	/// UUID of the version, used as partition key
-	pub uuid: Uuid,
-
-	// Actual data: the blocks for this version
-	// In the case of a multipart upload, also store the etags
-	// of individual parts and check them when doing CompleteMultipartUpload
-	/// Is this version deleted
-	pub deleted: crdt::Bool,
-	/// list of blocks of data composing the version
-	pub blocks: crdt::Map<VersionBlockKey, VersionBlock>,
-	/// Etag of each part in case of a multipart upload, empty otherwise
-	pub parts_etags: crdt::Map<u64, String>,
-
-	// Back link to bucket+key so that we can figure if
-	// this was deleted later on
-	/// Bucket in which the related object is stored
-	pub bucket: String,
-	/// Key in which the related object is stored
-	pub key: String,
-}
-
-#[derive(PartialEq, Eq, Clone, Copy, Debug, Serialize, Deserialize)]
-pub struct VersionBlockKey {
-	/// Number of the part
-	pub part_number: u64,
-	/// Offset of this sub-segment in its part
-	pub offset: u64,
-}
-
-impl Ord for VersionBlockKey {
-	fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-		self.part_number
-			.cmp(&other.part_number)
-			.then(self.offset.cmp(&other.offset))
-	}
-}
-
-impl PartialOrd for VersionBlockKey {
-	fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-		Some(self.cmp(other))
-	}
-}
-
-/// Informations about a single block
-#[derive(PartialEq, Eq, Ord, PartialOrd, Clone, Copy, Debug, Serialize, Deserialize)]
-pub struct VersionBlock {
-	/// Blake2 sum of the block
-	pub hash: Hash,
-	/// Size of the block
-	pub size: u64,
-}
-
-impl AutoCrdt for VersionBlock {
-	const WARN_IF_DIFFERENT: bool = true;
-}
-
-impl Crdt for Version {
-	fn merge(&mut self, other: &Self) {
-		self.deleted.merge(&other.deleted);
-
-		if self.deleted.get() {
-			self.blocks.clear();
-			self.parts_etags.clear();
-		} else {
-			self.blocks.merge(&other.blocks);
-			self.parts_etags.merge(&other.parts_etags);
-		}
-	}
-}
diff --git a/src/model/s3/block_ref_table.rs b/src/model/s3/block_ref_table.rs
index c7017409..7b023d87 100644
--- a/src/model/s3/block_ref_table.rs
+++ b/src/model/s3/block_ref_table.rs
@@ -1,4 +1,3 @@
-use serde::{Deserialize, Serialize};
 use std::sync::Arc;
 
 use garage_db as db;
@@ -10,19 +9,29 @@ use garage_table::*;
 
 use garage_block::manager::*;
 
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct BlockRef {
-	/// Hash (blake2 sum) of the block, used as partition key
-	pub block: Hash,
+mod v08 {
+	use garage_util::crdt;
+	use garage_util::data::{Hash, Uuid};
+	use serde::{Deserialize, Serialize};
 
-	/// Id of the Version for the object containing this block, used as sorting key
-	pub version: Uuid,
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct BlockRef {
+		/// Hash (blake2 sum) of the block, used as partition key
+		pub block: Hash,
 
-	// Keep track of deleted status
-	/// Is the Version that contains this block deleted
-	pub deleted: crdt::Bool,
+		/// Id of the Version for the object containing this block, used as sorting key
+		pub version: Uuid,
+
+		// Keep track of deleted status
+		/// Is the Version that contains this block deleted
+		pub deleted: crdt::Bool,
+	}
+
+	impl garage_util::migrate::InitialFormat for BlockRef {}
 }
 
+pub use v08::*;
+
 impl Entry<Hash, Uuid> for BlockRef {
 	fn partition_key(&self) -> &Hash {
 		&self.block
diff --git a/src/model/s3/object_table.rs b/src/model/s3/object_table.rs
index 1b2f0014..518acc95 100644
--- a/src/model/s3/object_table.rs
+++ b/src/model/s3/object_table.rs
@@ -1,5 +1,4 @@
 use serde::{Deserialize, Serialize};
-use std::collections::BTreeMap;
 use std::sync::Arc;
 
 use garage_db as db;
@@ -13,25 +12,126 @@ use garage_table::*;
 use crate::index_counter::*;
 use crate::s3::version_table::*;
 
-use crate::prev::v051::object_table as old;
-
 pub const OBJECTS: &str = "objects";
 pub const UNFINISHED_UPLOADS: &str = "unfinished_uploads";
 pub const BYTES: &str = "bytes";
 
-/// An object
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct Object {
-	/// The bucket in which the object is stored, used as partition key
-	pub bucket_id: Uuid,
+mod v05 {
+	use garage_util::data::{Hash, Uuid};
+	use serde::{Deserialize, Serialize};
+	use std::collections::BTreeMap;
+
+	/// An object
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct Object {
+		/// The bucket in which the object is stored, used as partition key
+		pub bucket: String,
+
+		/// The key at which the object is stored in its bucket, used as sorting key
+		pub key: String,
+
+		/// The list of currenty stored versions of the object
+		pub(super) versions: Vec<ObjectVersion>,
+	}
+
+	/// Informations about a version of an object
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct ObjectVersion {
+		/// Id of the version
+		pub uuid: Uuid,
+		/// Timestamp of when the object was created
+		pub timestamp: u64,
+		/// State of the version
+		pub state: ObjectVersionState,
+	}
+
+	/// State of an object version
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub enum ObjectVersionState {
+		/// The version is being received
+		Uploading(ObjectVersionHeaders),
+		/// The version is fully received
+		Complete(ObjectVersionData),
+		/// The version uploaded containded errors or the upload was explicitly aborted
+		Aborted,
+	}
+
+	/// Data stored in object version
+	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
+	pub enum ObjectVersionData {
+		/// The object was deleted, this Version is a tombstone to mark it as such
+		DeleteMarker,
+		/// The object is short, it's stored inlined
+		Inline(ObjectVersionMeta, #[serde(with = "serde_bytes")] Vec<u8>),
+		/// The object is not short, Hash of first block is stored here, next segments hashes are
+		/// stored in the version table
+		FirstBlock(ObjectVersionMeta, Hash),
+	}
+
+	/// Metadata about the object version
+	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
+	pub struct ObjectVersionMeta {
+		/// Headers to send to the client
+		pub headers: ObjectVersionHeaders,
+		/// Size of the object
+		pub size: u64,
+		/// etag of the object
+		pub etag: String,
+	}
+
+	/// Additional headers for an object
+	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
+	pub struct ObjectVersionHeaders {
+		/// Content type of the object
+		pub content_type: String,
+		/// Any other http headers to send
+		pub other: BTreeMap<String, String>,
+	}
+
+	impl garage_util::migrate::InitialFormat for Object {}
+}
+
+mod v08 {
+	use garage_util::data::Uuid;
+	use serde::{Deserialize, Serialize};
+
+	use super::v05;
 
-	/// The key at which the object is stored in its bucket, used as sorting key
-	pub key: String,
+	pub use v05::{
+		ObjectVersion, ObjectVersionData, ObjectVersionHeaders, ObjectVersionMeta,
+		ObjectVersionState,
+	};
+
+	/// An object
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct Object {
+		/// The bucket in which the object is stored, used as partition key
+		pub bucket_id: Uuid,
+
+		/// The key at which the object is stored in its bucket, used as sorting key
+		pub key: String,
+
+		/// The list of currenty stored versions of the object
+		pub(super) versions: Vec<ObjectVersion>,
+	}
 
-	/// The list of currenty stored versions of the object
-	versions: Vec<ObjectVersion>,
+	impl garage_util::migrate::Migrate for Object {
+		type Previous = v05::Object;
+
+		fn migrate(old: v05::Object) -> Object {
+			use garage_util::data::blake2sum;
+
+			Object {
+				bucket_id: blake2sum(old.bucket.as_bytes()),
+				key: old.key,
+				versions: old.versions,
+			}
+		}
+	}
 }
 
+pub use v08::*;
+
 impl Object {
 	/// Initialize an Object struct from parts
 	pub fn new(bucket_id: Uuid, key: String, versions: Vec<ObjectVersion>) -> Self {
@@ -68,28 +168,6 @@ impl Object {
 	}
 }
 
-/// Informations about a version of an object
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct ObjectVersion {
-	/// Id of the version
-	pub uuid: Uuid,
-	/// Timestamp of when the object was created
-	pub timestamp: u64,
-	/// State of the version
-	pub state: ObjectVersionState,
-}
-
-/// State of an object version
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub enum ObjectVersionState {
-	/// The version is being received
-	Uploading(ObjectVersionHeaders),
-	/// The version is fully received
-	Complete(ObjectVersionData),
-	/// The version uploaded containded errors or the upload was explicitly aborted
-	Aborted,
-}
-
 impl Crdt for ObjectVersionState {
 	fn merge(&mut self, other: &Self) {
 		use ObjectVersionState::*;
@@ -111,42 +189,10 @@ impl Crdt for ObjectVersionState {
 	}
 }
 
-/// Data stored in object version
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub enum ObjectVersionData {
-	/// The object was deleted, this Version is a tombstone to mark it as such
-	DeleteMarker,
-	/// The object is short, it's stored inlined
-	Inline(ObjectVersionMeta, #[serde(with = "serde_bytes")] Vec<u8>),
-	/// The object is not short, Hash of first block is stored here, next segments hashes are
-	/// stored in the version table
-	FirstBlock(ObjectVersionMeta, Hash),
-}
-
 impl AutoCrdt for ObjectVersionData {
 	const WARN_IF_DIFFERENT: bool = true;
 }
 
-/// Metadata about the object version
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub struct ObjectVersionMeta {
-	/// Headers to send to the client
-	pub headers: ObjectVersionHeaders,
-	/// Size of the object
-	pub size: u64,
-	/// etag of the object
-	pub etag: String,
-}
-
-/// Additional headers for an object
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub struct ObjectVersionHeaders {
-	/// Content type of the object
-	pub content_type: String,
-	/// Any other http headers to send
-	pub other: BTreeMap<String, String>,
-}
-
 impl ObjectVersion {
 	fn cmp_key(&self) -> (u64, Uuid) {
 		(self.timestamp, self.uuid)
@@ -290,11 +336,6 @@ impl TableSchema for ObjectTable {
 			ObjectFilter::IsUploading => entry.versions.iter().any(|v| v.is_uploading()),
 		}
 	}
-
-	fn try_migrate(bytes: &[u8]) -> Option<Self::E> {
-		let old_obj = rmp_serde::decode::from_read_ref::<_, old::Object>(bytes).ok()?;
-		Some(migrate_object(old_obj))
-	}
 }
 
 impl CountedItem for Object {
@@ -339,64 +380,3 @@ impl CountedItem for Object {
 		]
 	}
 }
-
-// vvvvvvvv migration code, stupid stuff vvvvvvvvvvvv
-// (we just want to change bucket into bucket_id by hashing it)
-
-fn migrate_object(o: old::Object) -> Object {
-	let versions = o
-		.versions()
-		.iter()
-		.cloned()
-		.map(migrate_object_version)
-		.collect();
-	Object {
-		bucket_id: blake2sum(o.bucket.as_bytes()),
-		key: o.key,
-		versions,
-	}
-}
-
-fn migrate_object_version(v: old::ObjectVersion) -> ObjectVersion {
-	ObjectVersion {
-		uuid: Uuid::try_from(v.uuid.as_slice()).unwrap(),
-		timestamp: v.timestamp,
-		state: match v.state {
-			old::ObjectVersionState::Uploading(h) => {
-				ObjectVersionState::Uploading(migrate_object_version_headers(h))
-			}
-			old::ObjectVersionState::Complete(d) => {
-				ObjectVersionState::Complete(migrate_object_version_data(d))
-			}
-			old::ObjectVersionState::Aborted => ObjectVersionState::Aborted,
-		},
-	}
-}
-
-fn migrate_object_version_headers(h: old::ObjectVersionHeaders) -> ObjectVersionHeaders {
-	ObjectVersionHeaders {
-		content_type: h.content_type,
-		other: h.other,
-	}
-}
-
-fn migrate_object_version_data(d: old::ObjectVersionData) -> ObjectVersionData {
-	match d {
-		old::ObjectVersionData::DeleteMarker => ObjectVersionData::DeleteMarker,
-		old::ObjectVersionData::Inline(m, b) => {
-			ObjectVersionData::Inline(migrate_object_version_meta(m), b)
-		}
-		old::ObjectVersionData::FirstBlock(m, h) => ObjectVersionData::FirstBlock(
-			migrate_object_version_meta(m),
-			Hash::try_from(h.as_slice()).unwrap(),
-		),
-	}
-}
-
-fn migrate_object_version_meta(m: old::ObjectVersionMeta) -> ObjectVersionMeta {
-	ObjectVersionMeta {
-		headers: migrate_object_version_headers(m.headers),
-		size: m.size,
-		etag: m.etag,
-	}
-}
diff --git a/src/model/s3/version_table.rs b/src/model/s3/version_table.rs
index 0486512b..6edc83f4 100644
--- a/src/model/s3/version_table.rs
+++ b/src/model/s3/version_table.rs
@@ -1,4 +1,3 @@
-use serde::{Deserialize, Serialize};
 use std::sync::Arc;
 
 use garage_db as db;
@@ -11,32 +10,108 @@ use garage_table::*;
 
 use crate::s3::block_ref_table::*;
 
-use crate::prev::v051::version_table as old;
-
-/// A version of an object
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
-pub struct Version {
-	/// UUID of the version, used as partition key
-	pub uuid: Uuid,
-
-	// Actual data: the blocks for this version
-	// In the case of a multipart upload, also store the etags
-	// of individual parts and check them when doing CompleteMultipartUpload
-	/// Is this version deleted
-	pub deleted: crdt::Bool,
-	/// list of blocks of data composing the version
-	pub blocks: crdt::Map<VersionBlockKey, VersionBlock>,
-	/// Etag of each part in case of a multipart upload, empty otherwise
-	pub parts_etags: crdt::Map<u64, String>,
-
-	// Back link to bucket+key so that we can figure if
-	// this was deleted later on
-	/// Bucket in which the related object is stored
-	pub bucket_id: Uuid,
-	/// Key in which the related object is stored
-	pub key: String,
+mod v05 {
+	use garage_util::crdt;
+	use garage_util::data::{Hash, Uuid};
+	use serde::{Deserialize, Serialize};
+
+	/// A version of an object
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct Version {
+		/// UUID of the version, used as partition key
+		pub uuid: Uuid,
+
+		// Actual data: the blocks for this version
+		// In the case of a multipart upload, also store the etags
+		// of individual parts and check them when doing CompleteMultipartUpload
+		/// Is this version deleted
+		pub deleted: crdt::Bool,
+		/// list of blocks of data composing the version
+		pub blocks: crdt::Map<VersionBlockKey, VersionBlock>,
+		/// Etag of each part in case of a multipart upload, empty otherwise
+		pub parts_etags: crdt::Map<u64, String>,
+
+		// Back link to bucket+key so that we can figure if
+		// this was deleted later on
+		/// Bucket in which the related object is stored
+		pub bucket: String,
+		/// Key in which the related object is stored
+		pub key: String,
+	}
+
+	#[derive(PartialEq, Eq, Clone, Copy, Debug, Serialize, Deserialize)]
+	pub struct VersionBlockKey {
+		/// Number of the part
+		pub part_number: u64,
+		/// Offset of this sub-segment in its part
+		pub offset: u64,
+	}
+
+	/// Informations about a single block
+	#[derive(PartialEq, Eq, Ord, PartialOrd, Clone, Copy, Debug, Serialize, Deserialize)]
+	pub struct VersionBlock {
+		/// Blake2 sum of the block
+		pub hash: Hash,
+		/// Size of the block
+		pub size: u64,
+	}
+
+	impl garage_util::migrate::InitialFormat for Version {}
+}
+
+mod v08 {
+	use garage_util::crdt;
+	use garage_util::data::Uuid;
+	use serde::{Deserialize, Serialize};
+
+	use super::v05;
+
+	/// A version of an object
+	#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+	pub struct Version {
+		/// UUID of the version, used as partition key
+		pub uuid: Uuid,
+
+		// Actual data: the blocks for this version
+		// In the case of a multipart upload, also store the etags
+		// of individual parts and check them when doing CompleteMultipartUpload
+		/// Is this version deleted
+		pub deleted: crdt::Bool,
+		/// list of blocks of data composing the version
+		pub blocks: crdt::Map<VersionBlockKey, VersionBlock>,
+		/// Etag of each part in case of a multipart upload, empty otherwise
+		pub parts_etags: crdt::Map<u64, String>,
+
+		// Back link to bucket+key so that we can figure if
+		// this was deleted later on
+		/// Bucket in which the related object is stored
+		pub bucket_id: Uuid,
+		/// Key in which the related object is stored
+		pub key: String,
+	}
+
+	pub use v05::{VersionBlock, VersionBlockKey};
+
+	impl garage_util::migrate::Migrate for Version {
+		type Previous = v05::Version;
+
+		fn migrate(old: v05::Version) -> Version {
+			use garage_util::data::blake2sum;
+
+			Version {
+				uuid: old.uuid,
+				deleted: old.deleted,
+				blocks: old.blocks,
+				parts_etags: old.parts_etags,
+				bucket_id: blake2sum(old.bucket.as_bytes()),
+				key: old.key,
+			}
+		}
+	}
 }
 
+pub use v08::*;
+
 impl Version {
 	pub fn new(uuid: Uuid, bucket_id: Uuid, key: String, deleted: bool) -> Self {
 		Self {
@@ -64,14 +139,6 @@ impl Version {
 	}
 }
 
-#[derive(PartialEq, Eq, Clone, Copy, Debug, Serialize, Deserialize)]
-pub struct VersionBlockKey {
-	/// Number of the part
-	pub part_number: u64,
-	/// Offset of this sub-segment in its part
-	pub offset: u64,
-}
-
 impl Ord for VersionBlockKey {
 	fn cmp(&self, other: &Self) -> std::cmp::Ordering {
 		self.part_number
@@ -86,15 +153,6 @@ impl PartialOrd for VersionBlockKey {
 	}
 }
 
-/// Informations about a single block
-#[derive(PartialEq, Eq, Ord, PartialOrd, Clone, Copy, Debug, Serialize, Deserialize)]
-pub struct VersionBlock {
-	/// Blake2 sum of the block
-	pub hash: Hash,
-	/// Size of the block
-	pub size: u64,
-}
-
 impl AutoCrdt for VersionBlock {
 	const WARN_IF_DIFFERENT: bool = true;
 }
@@ -166,42 +224,4 @@ impl TableSchema for VersionTable {
 	fn matches_filter(entry: &Self::E, filter: &Self::Filter) -> bool {
 		filter.apply(entry.deleted.get())
 	}
-
-	fn try_migrate(bytes: &[u8]) -> Option<Self::E> {
-		let old = rmp_serde::decode::from_read_ref::<_, old::Version>(bytes).ok()?;
-
-		let blocks = old
-			.blocks
-			.items()
-			.iter()
-			.map(|(k, v)| {
-				(
-					VersionBlockKey {
-						part_number: k.part_number,
-						offset: k.offset,
-					},
-					VersionBlock {
-						hash: Hash::try_from(v.hash.as_slice()).unwrap(),
-						size: v.size,
-					},
-				)
-			})
-			.collect::<crdt::Map<_, _>>();
-
-		let parts_etags = old
-			.parts_etags
-			.items()
-			.iter()
-			.map(|(k, v)| (*k, v.clone()))
-			.collect::<crdt::Map<_, _>>();
-
-		Some(Version {
-			uuid: Hash::try_from(old.uuid.as_slice()).unwrap(),
-			deleted: crdt::Bool::new(old.deleted.get()),
-			blocks,
-			parts_etags,
-			bucket_id: blake2sum(old.bucket.as_bytes()),
-			key: old.key,
-		})
-	}
 }