Store schema name in pg-roll's internal schema representation (#67)

Change the representation of a schema in `pg-roll`s state store from:

```go
type Schema struct {
	// Tables is a map of virtual table name -> table mapping
	Tables map[string]Table `json:"tables"`
}
```

to:

```go
type Schema struct {
	// Name is the name of the schema
	Name string `json:"name"`
	// Tables is a map of virtual table name -> table mapping
	Tables map[string]Table `json:"tables"`
}
```

ie, store the schema's name.

This allows the signature of `Start` to be simplified, removing the
`schemaName` parameter; the name can be retrieved from the
`schema.Schema` struct that is already provided.

pkg/migrations/migrations.go

@@ -12,7 +12,7 @@ type Operation interface {
 	// Start will apply the required changes to enable supporting the new schema
 	// version in the database (through a view)
 	// update the given views to expose the new schema version
-	Start(ctx context.Context, conn *sql.DB, schemaName, stateSchema string, s *schema.Schema) error
+	Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error
 
 	// Complete will update the database schema to match the current version
 	// after calling Start.

pkg/migrations/op_add_column.go

@@ -18,7 +18,7 @@ type OpAddColumn struct {
 
 var _ Operation = (*OpAddColumn)(nil)
 
-func (o *OpAddColumn) Start(ctx context.Context, conn *sql.DB, schemaName, stateSchema string, s *schema.Schema) error {
+func (o *OpAddColumn) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	table := s.GetTable(o.Table)
 
 	if err := addColumn(ctx, conn, *o, table); err != nil {
@@ -36,7 +36,7 @@ func (o *OpAddColumn) Start(ctx context.Context, conn *sql.DB, schemaName, state
 			Name:           TriggerName(o.Table, o.Column.Name),
 			Direction:      TriggerDirectionUp,
 			Columns:        s.GetTable(o.Table).Columns,
-			SchemaName:     schemaName,
+			SchemaName:     s.Name,
 			TableName:      o.Table,
 			PhysicalColumn: TemporaryName(o.Column.Name),
 			StateSchema:    stateSchema,

pkg/migrations/op_create_index.go

@@ -18,7 +18,7 @@ type OpCreateIndex struct {
 
 var _ Operation = (*OpCreateIndex)(nil)
 
-func (o *OpCreateIndex) Start(ctx context.Context, conn *sql.DB, schemaName string, stateSchema string, s *schema.Schema) error {
+func (o *OpCreateIndex) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	// create index concurrently
 	_, err := conn.ExecContext(ctx, fmt.Sprintf("CREATE INDEX CONCURRENTLY IF NOT EXISTS %s ON %s (%s)",
 		pq.QuoteIdentifier(o.Name),

pkg/migrations/op_create_table.go

@@ -25,7 +25,7 @@ type Column struct {
 	Default    *string `json:"default"`
 }
 
-func (o *OpCreateTable) Start(ctx context.Context, conn *sql.DB, schemaName, stateSchema string, s *schema.Schema) error {
+func (o *OpCreateTable) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	tempName := TemporaryName(o.Name)
 	_, err := conn.ExecContext(ctx, fmt.Sprintf("CREATE TABLE %s (%s)",
 		pq.QuoteIdentifier(tempName),

pkg/migrations/op_drop_column.go

@@ -17,13 +17,13 @@ type OpDropColumn struct {
 
 var _ Operation = (*OpDropColumn)(nil)
 
-func (o *OpDropColumn) Start(ctx context.Context, conn *sql.DB, schemaName string, stateSchema string, s *schema.Schema) error {
+func (o *OpDropColumn) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	if o.Down != nil {
 		err := createTrigger(ctx, conn, triggerConfig{
 			Name:           TriggerName(o.Table, o.Column),
 			Direction:      TriggerDirectionDown,
 			Columns:        s.GetTable(o.Table).Columns,
-			SchemaName:     schemaName,
+			SchemaName:     s.Name,
 			TableName:      o.Table,
 			PhysicalColumn: o.Column,
 			StateSchema:    stateSchema,

pkg/migrations/op_drop_index.go

@@ -14,7 +14,7 @@ type OpDropIndex struct {
 
 var _ Operation = (*OpDropIndex)(nil)
 
-func (o *OpDropIndex) Start(ctx context.Context, conn *sql.DB, schemaName string, stateSchema string, s *schema.Schema) error {
+func (o *OpDropIndex) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	// no-op
 	return nil
 }

pkg/migrations/op_drop_table.go

@@ -15,7 +15,7 @@ type OpDropTable struct {
 
 var _ Operation = (*OpDropTable)(nil)
 
-func (o *OpDropTable) Start(ctx context.Context, conn *sql.DB, schemaName, stateSchema string, s *schema.Schema) error {
+func (o *OpDropTable) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	s.RemoveTable(o.Name)
 	return nil
 }

pkg/migrations/op_rename_column.go

@@ -17,7 +17,7 @@ type OpRenameColumn struct {
 
 var _ Operation = (*OpRenameColumn)(nil)
 
-func (o *OpRenameColumn) Start(ctx context.Context, conn *sql.DB, schemaName string, stateSchema string, s *schema.Schema) error {
+func (o *OpRenameColumn) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	table := s.GetTable(o.Table)
 	table.RenameColumn(o.From, o.To)
 	return nil

pkg/migrations/op_rename_table.go

@@ -16,7 +16,7 @@ type OpRenameTable struct {
 	To   string `json:"to"`
 }
 
-func (o *OpRenameTable) Start(ctx context.Context, conn *sql.DB, schemaName, stateSchema string, s *schema.Schema) error {
+func (o *OpRenameTable) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	return s.RenameTable(o.From, o.To)
 }
 

pkg/migrations/op_set_notnull.go

@@ -17,7 +17,7 @@ type OpSetNotNull struct {
 
 var _ Operation = (*OpSetNotNull)(nil)
 
-func (o *OpSetNotNull) Start(ctx context.Context, conn *sql.DB, schemaName string, stateSchema string, s *schema.Schema) error {
+func (o *OpSetNotNull) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	table := s.GetTable(o.Table)
 	column := table.GetColumn(o.Column)
 
@@ -36,7 +36,7 @@ func (o *OpSetNotNull) Start(ctx context.Context, conn *sql.DB, schemaName strin
 		Name:           TriggerName(o.Table, o.Column),
 		Direction:      TriggerDirectionUp,
 		Columns:        table.Columns,
-		SchemaName:     schemaName,
+		SchemaName:     s.Name,
 		TableName:      o.Table,
 		PhysicalColumn: TemporaryName(o.Column),
 		StateSchema:    stateSchema,
@@ -60,7 +60,7 @@ func (o *OpSetNotNull) Start(ctx context.Context, conn *sql.DB, schemaName strin
 		Name:           TriggerName(o.Table, TemporaryName(o.Column)),
 		Direction:      TriggerDirectionDown,
 		Columns:        table.Columns,
-		SchemaName:     schemaName,
+		SchemaName:     s.Name,
 		TableName:      o.Table,
 		PhysicalColumn: o.Column,
 		StateSchema:    stateSchema,

pkg/migrations/op_set_unique.go

@@ -18,7 +18,7 @@ type OpSetUnique struct {
 
 var _ Operation = (*OpSetUnique)(nil)
 
-func (o *OpSetUnique) Start(ctx context.Context, conn *sql.DB, schemaName string, stateSchema string, s *schema.Schema) error {
+func (o *OpSetUnique) Start(ctx context.Context, conn *sql.DB, stateSchema string, s *schema.Schema) error {
 	// create unique index concurrently
 	_, err := conn.ExecContext(ctx, fmt.Sprintf("CREATE UNIQUE INDEX CONCURRENTLY IF NOT EXISTS %s ON %s (%s)",
 		pq.QuoteIdentifier(o.Name),

pkg/roll/execute.go

@@ -38,7 +38,7 @@ func (m *Roll) Start(ctx context.Context, migration *migrations.Migration) error
 
 	// execute operations
 	for _, op := range migration.Operations {
-		err := op.Start(ctx, m.pgConn, m.schema, m.state.Schema(), newSchema)
+		err := op.Start(ctx, m.pgConn, m.state.Schema(), newSchema)
 		if err != nil {
 			return fmt.Errorf("unable to execute start operation: %w", err)
 		}

pkg/schema/schema.go

@@ -15,6 +15,8 @@ func New() *Schema {
 }
 
 type Schema struct {
+	// Name is the name of the schema
+	Name string `json:"name"`
 	// Tables is a map of virtual table name -> table mapping
 	Tables map[string]Table `json:"tables"`
 }

pkg/state/state.go

@@ -73,6 +73,7 @@ DECLARE
 	tables jsonb;
 BEGIN
 	SELECT json_build_object(
+		'name', schemaname,
 		'tables', (
 			SELECT json_object_agg(t.relname, jsonb_build_object(
 				'name', t.relname,