api: write a connection schema getter

Write a helper function to load the actual schema for the user.

Previously we stored actual schema in a private `schemaResolver`
field and `Schema` field was used only to get a current schema.
But now because of the new function, we don't need to store the
`Schema` as a different field. So `Schema` was also removed.

To update the schema, one needs to use `GetSchema` + `SetSchema`
in pair. `SetSchema(Schema)` replacing the `OverrideSchema(*Schema)`.

`Spaces` and `SpacesById` fields of the `Schema` struct store spaces by value.
`Fields` and `FieldsById` fields of the `Space` struct store fields by value.
`Index` and `IndexById` fields of the `Space` struct store indexes by value.
`Fields` field of the `Index` struct store `IndexField` by value.

Closes #7

Author: DerekBum

Diff for: CHANGELOG.md

@@ -26,6 +26,7 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
 - Support `IPROTO_FEATURE_SPACE_AND_INDEX_NAMES` for Tarantool
   version >= 3.0.0-alpha1 (#338). It allows to use space and index names 
   in requests instead of their IDs.
+- `GetSchema` function to get the actual schema (#7)
 
 ### Changed
 
@@ -51,6 +52,9 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
   instead of `crud.OptUint` (#342)
 - Change all `Upsert` and `Update` requests to accept `*tarantool.Operations` 
   as `ops` parameters instead of `interface{}` (#348)
+- Change `OverrideSchema(*Schema)` to `SetSchema(Schema)` (#7)
+- Change values, stored by pointers in the `Schema`, `Space`, `Index` structs, 
+  to be stored by their values (#7)
 
 ### Deprecated
 
@@ -70,6 +74,7 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
 - UUID_extId (#158)
 - IPROTO constants (#158)
 - Code() method from the Request interface (#158)
+- `Schema` field from the `Connection` struct (#7)
 
 ### Fixed
 

Diff for: README.md

@@ -248,6 +248,13 @@ now does not attempt to reconnect and tries to establish a connection only once.
 Function might be canceled via context. Context accepted as first argument, 
 and user may cancel it in process.
 
+#### Connection schema
+
+* Removed `Schema` field from the `Connection` struct. Instead, new 
+`GetSchema(Connector)` function was added to get the actual connection 
+schema on demand.
+* `OverrideSchema(*Schema)` method replaced with the `SetSchema(Schema)`.
+
 #### Protocol changes
 
 * `iproto.Feature` type used instead of `ProtocolFeature`.
@@ -260,6 +267,10 @@ and user may cancel it in process.
 interface to get information if the usage of space and index names in requests 
 is supported.
 * `Schema` structure no longer implements `SchemaResolver` interface.
+* `Spaces` and `SpacesById` fields of the `Schema` struct store spaces by value.
+* `Fields` and `FieldsById` fields of the `Space` struct store fields by value.
+`Index` and `IndexById` fields of the `Space` struct store indexes by value.
+* `Fields` field of the `Index` struct store `IndexField` by value.
 
 ## Contributing
 

Diff for: connection.go

@@ -160,8 +160,6 @@ type Connection struct {
 	c     Conn
 	mutex sync.Mutex
 	cond  *sync.Cond
-	// Schema contains schema loaded on connection.
-	Schema *Schema
 	// schemaResolver contains a SchemaResolver implementation.
 	schemaResolver SchemaResolver
 	// requestId contains the last request ID for requests with nil context.
@@ -436,12 +434,14 @@ func Connect(ctx context.Context, addr string, opts Opts) (conn *Connection, err
 
 	// TODO: reload schema after reconnect.
 	if !conn.opts.SkipSchema {
-		if err = conn.loadSchema(); err != nil {
+		schema, err := GetSchema(conn)
+		if err != nil {
 			conn.mutex.Lock()
 			defer conn.mutex.Unlock()
 			conn.closeConnection(err, true)
 			return nil, err
 		}
+		conn.SetSchema(schema)
 	}
 
 	return conn, err
@@ -1302,15 +1302,21 @@ func (conn *Connection) ConfiguredTimeout() time.Duration {
 	return conn.opts.Timeout
 }
 
-// OverrideSchema sets Schema for the connection.
-func (conn *Connection) OverrideSchema(s *Schema) {
-	if s != nil {
-		conn.mutex.Lock()
-		defer conn.mutex.Unlock()
-		conn.lockShards()
-		defer conn.unlockShards()
+// SetSchema sets Schema for the connection.
+func (conn *Connection) SetSchema(s Schema) {
+	sCopy := s.copy()
+	spaceAndIndexNamesSupported :=
+		isFeatureInSlice(iproto.IPROTO_FEATURE_SPACE_AND_INDEX_NAMES,
+			conn.serverProtocolInfo.Features)
 
-		conn.Schema = s
+	conn.mutex.Lock()
+	defer conn.mutex.Unlock()
+	conn.lockShards()
+	defer conn.unlockShards()
+
+	conn.schemaResolver = &loadedSchemaResolver{
+		Schema:                      sCopy,
+		SpaceAndIndexNamesSupported: spaceAndIndexNamesSupported,
 	}
 }
 

Diff for: example_test.go

@@ -1063,7 +1063,10 @@ func ExampleSchema() {
 	conn := exampleConnect(opts)
 	defer conn.Close()
 
-	schema := conn.Schema
+	schema, err := tarantool.GetSchema(conn)
+	if err != nil {
+		fmt.Printf("unexpected error: %s\n", err.Error())
+	}
 	if schema.SpacesById == nil {
 		fmt.Println("schema.SpacesById is nil")
 	}
@@ -1080,13 +1083,30 @@ func ExampleSchema() {
 	// Space 2 ID 616 schematest
 }
 
+// Example demonstrates how to update the connection schema.
+func ExampleConnection_SetSchema() {
+	conn := exampleConnect(opts)
+	defer conn.Close()
+
+	// Get the actual schema.
+	schema, err := tarantool.GetSchema(conn)
+	if err != nil {
+		fmt.Printf("unexpected error: %s\n", err.Error())
+	}
+	// Update the current schema to match the actual one.
+	conn.SetSchema(schema)
+}
+
 // Example demonstrates how to retrieve information with space schema.
 func ExampleSpace() {
 	conn := exampleConnect(opts)
 	defer conn.Close()
 
 	// Save Schema to a local variable to avoid races
-	schema := conn.Schema
+	schema, err := tarantool.GetSchema(conn)
+	if err != nil {
+		fmt.Printf("unexpected error: %s\n", err.Error())
+	}
 	if schema.SpacesById == nil {
 		fmt.Println("schema.SpacesById is nil")
 	}
@@ -1120,7 +1140,7 @@ func ExampleSpace() {
 	// Space 1 ID 617 test memtx
 	// Space 1 ID 0 false
 	// Index 0 primary
-	// &{0 unsigned} &{2 string}
+	// {0 unsigned} {2 string}
 	// SpaceField 1 name0 unsigned
 	// SpaceField 2 name3 unsigned
 }

Diff for: schema.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 
-	"github.com/tarantool/go-iproto"
 	"github.com/vmihailenco/msgpack/v5"
 	"github.com/vmihailenco/msgpack/v5/msgpcode"
 )
@@ -58,9 +57,22 @@ type SchemaResolver interface {
 type Schema struct {
 	Version uint
 	// Spaces is map from space names to spaces.
-	Spaces map[string]*Space
+	Spaces map[string]Space
 	// SpacesById is map from space numbers to spaces.
-	SpacesById map[uint32]*Space
+	SpacesById map[uint32]Space
+}
+
+func (schema *Schema) copy() Schema {
+	schemaCopy := *schema
+	schemaCopy.Spaces = make(map[string]Space, len(schema.Spaces))
+	for name, space := range schema.Spaces {
+		schemaCopy.Spaces[name] = space.copy()
+	}
+	schemaCopy.SpacesById = make(map[uint32]Space, len(schema.SpacesById))
+	for id, space := range schema.SpacesById {
+		schemaCopy.SpacesById[id] = space.copy()
+	}
+	return schemaCopy
 }
 
 // Space contains information about Tarantool's space.
@@ -72,12 +84,33 @@ type Space struct {
 	Temporary bool // Is this space temporary?
 	// Field configuration is not mandatory and not checked by Tarantool.
 	FieldsCount uint32
-	Fields      map[string]*Field
-	FieldsById  map[uint32]*Field
+	Fields      map[string]Field
+	FieldsById  map[uint32]Field
 	// Indexes is map from index names to indexes.
-	Indexes map[string]*Index
+	Indexes map[string]Index
 	// IndexesById is map from index numbers to indexes.
-	IndexesById map[uint32]*Index
+	IndexesById map[uint32]Index
+}
+
+func (space *Space) copy() Space {
+	spaceCopy := *space
+	spaceCopy.Fields = make(map[string]Field, len(space.Fields))
+	for name, field := range space.Fields {
+		spaceCopy.Fields[name] = field
+	}
+	spaceCopy.FieldsById = make(map[uint32]Field, len(space.FieldsById))
+	for id, field := range space.FieldsById {
+		spaceCopy.FieldsById[id] = field
+	}
+	spaceCopy.Indexes = make(map[string]Index, len(space.Indexes))
+	for name, index := range space.Indexes {
+		spaceCopy.Indexes[name] = index.copy()
+	}
+	spaceCopy.IndexesById = make(map[uint32]Index, len(space.IndexesById))
+	for id, index := range space.IndexesById {
+		spaceCopy.IndexesById[id] = index.copy()
+	}
+	return spaceCopy
 }
 
 func (space *Space) DecodeMsgpack(d *msgpack.Decoder) error {
@@ -135,17 +168,17 @@ func (space *Space) DecodeMsgpack(d *msgpack.Decoder) error {
 			return errors.New("unexpected schema format (space flags)")
 		}
 	}
-	space.FieldsById = make(map[uint32]*Field)
-	space.Fields = make(map[string]*Field)
-	space.IndexesById = make(map[uint32]*Index)
-	space.Indexes = make(map[string]*Index)
+	space.FieldsById = make(map[uint32]Field)
+	space.Fields = make(map[string]Field)
+	space.IndexesById = make(map[uint32]Index)
+	space.Indexes = make(map[string]Index)
 	if arrayLen >= vspaceSpFormatFieldNum {
 		fieldCount, err := d.DecodeArrayLen()
 		if err != nil {
 			return err
 		}
 		for i := 0; i < fieldCount; i++ {
-			field := &Field{}
+			field := Field{}
 			if err := field.DecodeMsgpack(d); err != nil {
 				return err
 			}
@@ -206,7 +239,14 @@ type Index struct {
 	Name    string
 	Type    string
 	Unique  bool
-	Fields  []*IndexField
+	Fields  []IndexField
+}
+
+func (index *Index) copy() Index {
+	indexCopy := *index
+	indexCopy.Fields = make([]IndexField, len(index.Fields))
+	copy(indexCopy.Fields, index.Fields)
+	return indexCopy
 }
 
 func (index *Index) DecodeMsgpack(d *msgpack.Decoder) error {
@@ -261,9 +301,9 @@ func (index *Index) DecodeMsgpack(d *msgpack.Decoder) error {
 		if err != nil {
 			return err
 		}
-		index.Fields = make([]*IndexField, fieldCount)
+		index.Fields = make([]IndexField, fieldCount)
 		for i := 0; i < int(fieldCount); i++ {
-			index.Fields[i] = new(IndexField)
+			index.Fields[i] = IndexField{}
 			if index.Fields[i].Id, err = d.DecodeUint32(); err != nil {
 				return err
 			}
@@ -340,51 +380,40 @@ func (indexField *IndexField) DecodeMsgpack(d *msgpack.Decoder) error {
 	return errors.New("unexpected schema format (index fields)")
 }
 
-func (conn *Connection) loadSchema() (err error) {
-	schema := new(Schema)
-	schema.SpacesById = make(map[uint32]*Space)
-	schema.Spaces = make(map[string]*Space)
+// GetSchema returns the actual schema for the connection.
+func GetSchema(conn Connector) (Schema, error) {
+	schema := Schema{}
+	schema.SpacesById = make(map[uint32]Space)
+	schema.Spaces = make(map[string]Space)
 
 	// Reload spaces.
-	var spaces []*Space
-	err = conn.SelectTyped(vspaceSpId, 0, 0, maxSchemas, IterAll, []interface{}{}, &spaces)
+	var spaces []Space
+	err := conn.SelectTyped(vspaceSpId, 0, 0, maxSchemas, IterAll, []interface{}{}, &spaces)
 	if err != nil {
-		return err
+		return Schema{}, err
 	}
 	for _, space := range spaces {
 		schema.SpacesById[space.Id] = space
 		schema.Spaces[space.Name] = space
 	}
 
 	// Reload indexes.
-	var indexes []*Index
+	var indexes []Index
 	err = conn.SelectTyped(vindexSpId, 0, 0, maxSchemas, IterAll, []interface{}{}, &indexes)
 	if err != nil {
-		return err
+		return Schema{}, err
 	}
 	for _, index := range indexes {
 		spaceId := index.SpaceId
 		if _, ok := schema.SpacesById[spaceId]; ok {
 			schema.SpacesById[spaceId].IndexesById[index.Id] = index
 			schema.SpacesById[spaceId].Indexes[index.Name] = index
 		} else {
-			return errors.New("concurrent schema update")
+			return Schema{}, errors.New("concurrent schema update")
 		}
 	}
 
-	spaceAndIndexNamesSupported :=
-		isFeatureInSlice(iproto.IPROTO_FEATURE_SPACE_AND_INDEX_NAMES,
-			conn.serverProtocolInfo.Features)
-
-	conn.lockShards()
-	conn.Schema = schema
-	conn.schemaResolver = &loadedSchemaResolver{
-		Schema:                      schema,
-		SpaceAndIndexNamesSupported: spaceAndIndexNamesSupported,
-	}
-	conn.unlockShards()
-
-	return nil
+	return schema, nil
 }
 
 // resolveSpaceNumber tries to resolve a space number.
@@ -462,7 +491,7 @@ func resolveIndexNumber(i interface{}) (uint32, error) {
 }
 
 type loadedSchemaResolver struct {
-	Schema *Schema
+	Schema Schema
 	// SpaceAndIndexNamesSupported shows if a current Tarantool version supports
 	// iproto.IPROTO_FEATURE_SPACE_AND_INDEX_NAMES.
 	SpaceAndIndexNamesSupported bool