feat: Allow setting of default schema version (#1888)

## Relevant issue(s)

Resolves #1884

## Description

Allows setting of default schema version, allowing rapid switching
between (application) api/database versions. It also allows them to
define and apply schema updates eagerly, and then make the switch at a
later date.

api/http/handlerfuncs.go

@@ -271,7 +271,10 @@ func patchSchemaHandler(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	err = db.PatchSchema(req.Context(), string(patch))
+	// Hardcode setDefault to true here, as that preserves the existing behaviour.
+	// This function will be ripped out very shortly and I don't think it is worth
+	// spending time/thought here.  The new http api handles this correctly.
+	err = db.PatchSchema(req.Context(), string(patch), true)
 	if err != nil {
 		handleErr(req.Context(), rw, err, http.StatusInternalServerError)
 		return

client/db.go

@@ -96,7 +96,8 @@ type Store interface {
 	AddSchema(context.Context, string) ([]CollectionDescription, error)
 
 	// PatchSchema takes the given JSON patch string and applies it to the set of CollectionDescriptions
-	// present in the database.
+	// present in the database. If true is provided, the new schema versions will be made default, otherwise
+	// [SetDefaultSchemaVersion] should be called to set them so.
 	//
 	// It will also update the GQL types used by the query system. It will error and not apply any of the
 	// requested, valid updates should the net result of the patch result in an invalid state.  The
@@ -109,7 +110,16 @@ type Store interface {
 	//
 	// Field [FieldKind] values may be provided in either their raw integer form, or as string as per
 	// [FieldKindStringToEnumMapping].
-	PatchSchema(context.Context, string) error
+	PatchSchema(context.Context, string, bool) error
+
+	// SetDefaultSchemaVersion sets the default schema version to the ID provided.  It will be applied to all
+	// collections using the schema.
+	//
+	// This will affect all operations interacting with the schema where a schema version is not explicitly
+	// provided.  This includes GQL queries and Collection operations.
+	//
+	// It will return an error if the provided schema version ID does not exist.
+	SetDefaultSchemaVersion(context.Context, string) error
 
 	// SetMigration sets the migration for the given source-destination schema version IDs. Is equivilent to
 	// calling `LensRegistry().SetMigration(ctx, cfg)`.

db/collection.go

@@ -234,6 +234,7 @@ func (db *db) updateCollection(
 	existingDescriptionsByName map[string]client.CollectionDescription,
 	proposedDescriptionsByName map[string]client.CollectionDescription,
 	desc client.CollectionDescription,
+	setAsDefaultVersion bool,
 ) (client.Collection, error) {
 	hasChanged, err := db.validateUpdateCollection(ctx, txn, existingDescriptionsByName, proposedDescriptionsByName, desc)
 	if err != nil {
@@ -300,24 +301,19 @@ func (db *db) updateCollection(
 		return nil, err
 	}
 
-	collectionSchemaKey := core.NewCollectionSchemaKey(desc.Schema.SchemaID)
-	err = txn.Systemstore().Put(ctx, collectionSchemaKey.ToDS(), []byte(schemaVersionID))
-	if err != nil {
-		return nil, err
-	}
-
-	collectionKey := core.NewCollectionKey(desc.Name)
-	err = txn.Systemstore().Put(ctx, collectionKey.ToDS(), []byte(schemaVersionID))
-	if err != nil {
-		return nil, err
-	}
-
 	schemaVersionHistoryKey := core.NewSchemaHistoryKey(desc.Schema.SchemaID, previousSchemaVersionID)
 	err = txn.Systemstore().Put(ctx, schemaVersionHistoryKey.ToDS(), []byte(schemaVersionID))
 	if err != nil {
 		return nil, err
 	}
 
+	if setAsDefaultVersion {
+		err = db.setDefaultSchemaVersionExplicit(ctx, txn, desc.Name, desc.Schema.SchemaID, schemaVersionID)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	return db.getCollectionByName(ctx, txn, desc.Name)
 }
 
@@ -591,6 +587,47 @@ func validateUpdateCollectionIndexes(
 	return false, nil
 }
 
+func (db *db) setDefaultSchemaVersion(
+	ctx context.Context,
+	txn datastore.Txn,
+	schemaVersionID string,
+) error {
+	col, err := db.getCollectionByVersionID(ctx, txn, schemaVersionID)
+	if err != nil {
+		return err
+	}
+
+	desc := col.Description()
+	err = db.setDefaultSchemaVersionExplicit(ctx, txn, desc.Name, desc.Schema.SchemaID, schemaVersionID)
+	if err != nil {
+		return err
+	}
+
+	cols, err := db.getCollectionDescriptions(ctx, txn)
+	if err != nil {
+		return err
+	}
+
+	return db.parser.SetSchema(ctx, txn, cols)
+}
+
+func (db *db) setDefaultSchemaVersionExplicit(
+	ctx context.Context,
+	txn datastore.Txn,
+	collectionName string,
+	schemaID string,
+	schemaVersionID string,
+) error {
+	collectionSchemaKey := core.NewCollectionSchemaKey(schemaID)
+	err := txn.Systemstore().Put(ctx, collectionSchemaKey.ToDS(), []byte(schemaVersionID))
+	if err != nil {
+		return err
+	}
+
+	collectionKey := core.NewCollectionKey(collectionName)
+	return txn.Systemstore().Put(ctx, collectionKey.ToDS(), []byte(schemaVersionID))
+}
+
 // getCollectionByVersionId returns the [*collection] at the given [schemaVersionId] version.
 //
 // Will return an error if the given key is empty, or not found.

db/schema.go

@@ -103,7 +103,7 @@ func (db *db) getCollectionDescriptions(
 // The collections (including the schema version ID) will only be updated if any changes have actually
 // been made, if the net result of the patch matches the current persisted description then no changes
 // will be applied.
-func (db *db) patchSchema(ctx context.Context, txn datastore.Txn, patchString string) error {
+func (db *db) patchSchema(ctx context.Context, txn datastore.Txn, patchString string, setAsDefaultVersion bool) error {
 	patch, err := jsonpatch.DecodePatch([]byte(patchString))
 	if err != nil {
 		return err
@@ -144,10 +144,11 @@ func (db *db) patchSchema(ctx context.Context, txn datastore.Txn, patchString st
 	}
 
 	for i, desc := range newDescriptions {
-		col, err := db.updateCollection(ctx, txn, collectionsByName, newDescriptionsByName, desc)
+		col, err := db.updateCollection(ctx, txn, collectionsByName, newDescriptionsByName, desc, setAsDefaultVersion)
 		if err != nil {
 			return err
 		}
+
 		newDescriptions[i] = col.Description()
 	}
 

db/txn_db.go

@@ -250,14 +250,14 @@ func (db *explicitTxnDB) AddSchema(ctx context.Context, schemaString string) ([]
 // The collections (including the schema version ID) will only be updated if any changes have actually
 // been made, if the net result of the patch matches the current persisted description then no changes
 // will be applied.
-func (db *implicitTxnDB) PatchSchema(ctx context.Context, patchString string) error {
+func (db *implicitTxnDB) PatchSchema(ctx context.Context, patchString string, setAsDefaultVersion bool) error {
 	txn, err := db.NewTxn(ctx, false)
 	if err != nil {
 		return err
 	}
 	defer txn.Discard(ctx)
 
-	err = db.patchSchema(ctx, txn, patchString)
+	err = db.patchSchema(ctx, txn, patchString, setAsDefaultVersion)
 	if err != nil {
 		return err
 	}
@@ -276,8 +276,27 @@ func (db *implicitTxnDB) PatchSchema(ctx context.Context, patchString string) er
 // The collections (including the schema version ID) will only be updated if any changes have actually
 // been made, if the net result of the patch matches the current persisted description then no changes
 // will be applied.
-func (db *explicitTxnDB) PatchSchema(ctx context.Context, patchString string) error {
-	return db.patchSchema(ctx, db.txn, patchString)
+func (db *explicitTxnDB) PatchSchema(ctx context.Context, patchString string, setAsDefaultVersion bool) error {
+	return db.patchSchema(ctx, db.txn, patchString, setAsDefaultVersion)
+}
+
+func (db *implicitTxnDB) SetDefaultSchemaVersion(ctx context.Context, schemaVersionID string) error {
+	txn, err := db.NewTxn(ctx, false)
+	if err != nil {
+		return err
+	}
+	defer txn.Discard(ctx)
+
+	err = db.setDefaultSchemaVersion(ctx, txn, schemaVersionID)
+	if err != nil {
+		return err
+	}
+
+	return txn.Commit(ctx)
+}
+
+func (db *explicitTxnDB) SetDefaultSchemaVersion(ctx context.Context, schemaVersionID string) error {
+	return db.setDefaultSchemaVersion(ctx, db.txn, schemaVersionID)
 }
 
 func (db *implicitTxnDB) SetMigration(ctx context.Context, cfg client.LensConfig) error {

http/client.go

@@ -212,10 +212,31 @@ func (c *Client) AddSchema(ctx context.Context, schema string) ([]client.Collect
 	return cols, nil
 }
 
-func (c *Client) PatchSchema(ctx context.Context, patch string) error {
+type patchSchemaRequest struct {
+	Patch               string
+	SetAsDefaultVersion bool
+}
+
+func (c *Client) PatchSchema(ctx context.Context, patch string, setAsDefaultVersion bool) error {
 	methodURL := c.http.baseURL.JoinPath("schema")
 
-	req, err := http.NewRequestWithContext(ctx, http.MethodPatch, methodURL.String(), strings.NewReader(patch))
+	body, err := json.Marshal(patchSchemaRequest{patch, setAsDefaultVersion})
+	if err != nil {
+		return err
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPatch, methodURL.String(), bytes.NewBuffer(body))
+	if err != nil {
+		return err
+	}
+	_, err = c.http.request(req)
+	return err
+}
+
+func (c *Client) SetDefaultSchemaVersion(ctx context.Context, schemaVersionID string) error {
+	methodURL := c.http.baseURL.JoinPath("schema", "default")
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, methodURL.String(), strings.NewReader(schemaVersionID))
 	if err != nil {
 		return err
 	}

http/handler_store.go

@@ -151,12 +151,30 @@ func (s *storeHandler) AddSchema(rw http.ResponseWriter, req *http.Request) {
 func (s *storeHandler) PatchSchema(rw http.ResponseWriter, req *http.Request) {
 	store := req.Context().Value(storeContextKey).(client.Store)
 
-	patch, err := io.ReadAll(req.Body)
+	var message patchSchemaRequest
+	err := requestJSON(req, &message)
 	if err != nil {
 		responseJSON(rw, http.StatusBadRequest, errorResponse{err})
 		return
 	}
-	err = store.PatchSchema(req.Context(), string(patch))
+
+	err = store.PatchSchema(req.Context(), message.Patch, message.SetAsDefaultVersion)
+	if err != nil {
+		responseJSON(rw, http.StatusBadRequest, errorResponse{err})
+		return
+	}
+	rw.WriteHeader(http.StatusOK)
+}
+
+func (s *storeHandler) SetDefaultSchemaVersion(rw http.ResponseWriter, req *http.Request) {
+	store := req.Context().Value(storeContextKey).(client.Store)
+
+	schemaVersionID, err := io.ReadAll(req.Body)
+	if err != nil {
+		responseJSON(rw, http.StatusBadRequest, errorResponse{err})
+		return
+	}
+	err = store.SetDefaultSchemaVersion(req.Context(), string(schemaVersionID))
 	if err != nil {
 		responseJSON(rw, http.StatusBadRequest, errorResponse{err})
 		return

http/server.go

@@ -54,6 +54,7 @@ func NewServer(db client.DB) *Server {
 		api.Route("/schema", func(schema chi.Router) {
 			schema.Post("/", store_handler.AddSchema)
 			schema.Patch("/", store_handler.PatchSchema)
+			schema.Post("/default", store_handler.SetDefaultSchemaVersion)
 		})
 		api.Route("/collections", func(collections chi.Router) {
 			collections.Get("/", store_handler.GetCollection)

http/wrapper.go

@@ -86,8 +86,12 @@ func (w *Wrapper) AddSchema(ctx context.Context, schema string) ([]client.Collec
 	return w.client.AddSchema(ctx, schema)
 }
 
-func (w *Wrapper) PatchSchema(ctx context.Context, patch string) error {
-	return w.client.PatchSchema(ctx, patch)
+func (w *Wrapper) PatchSchema(ctx context.Context, patch string, setAsDefaultVersion bool) error {
+	return w.client.PatchSchema(ctx, patch, setAsDefaultVersion)
+}
+
+func (w *Wrapper) SetDefaultSchemaVersion(ctx context.Context, schemaVersionID string) error {
+	return w.client.SetDefaultSchemaVersion(ctx, schemaVersionID)
 }
 
 func (w *Wrapper) SetMigration(ctx context.Context, config client.LensConfig) error {