chore: import upstream snapshot with attribution

core/schema.go

@@ -0,0 +1,49 @@
+// Copyright 2024 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package core
+
+import (
+	"github.com/dolthub/dolt/go/libraries/doltcore/sqle/resolve"
+	"github.com/dolthub/go-mysql-server/sql"
+)
+
+// GetCurrentSchema returns the current schema used by the context. Defaults to "public" if the context does not specify
+// a schema.
+func GetCurrentSchema(ctx *sql.Context) (string, error) {
+	_, root, err := GetRootFromContext(ctx)
+	if err != nil {
+		return "", nil
+	}
+
+	return resolve.FirstExistingSchemaOnSearchPath(ctx, root)
+}
+
+// GetSchemaName returns the schema name if there is any exist.
+// If the given schema is not empty, it's returned.
+// If it is empty, uses given database to get schema name if it's DatabaseSchema.
+// If it's not of DatabaseSchema type or the schema name of it is empty,
+// it tries retrieving the current schema used by the context.
+// Defaults to "public" if the context does not specify a schema.
+func GetSchemaName(ctx *sql.Context, db sql.Database, schemaName string) (string, error) {
+	if schemaName == "" {
+		if schema, isSch := db.(sql.DatabaseSchema); isSch {
+			schemaName = schema.SchemaName()
+		}
+		if schemaName == "" {
+			return GetCurrentSchema(ctx)
+		}
+	}
+	return schemaName, nil
+}