docs: add sample for PDML (#53)

examples/partitioned-dml/main.go

@@ -0,0 +1,85 @@
+// Copyright 2021 Google LLC
+//
+// 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
+//
+//     https://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 main
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"cloud.google.com/go/spanner"
+	_ "github.com/cloudspannerecosystem/go-sql-spanner"
+	spannerdriver "github.com/cloudspannerecosystem/go-sql-spanner"
+	"github.com/cloudspannerecosystem/go-sql-spanner/examples"
+)
+
+var createTableStatement = "CREATE TABLE Singers (SingerId INT64, Name STRING(MAX)) PRIMARY KEY (SingerId)"
+
+// Example for executing a Partitioned DML transaction on a Google Cloud Spanner database.
+// See https://cloud.google.com/spanner/docs/dml-partitioned for more information on Partitioned DML.
+//
+// Execute the sample with the command `go run main.go` from this directory.
+func partitionedDml(projectId, instanceId, databaseId string) error {
+	ctx := context.Background()
+	db, err := sql.Open("spanner", fmt.Sprintf("projects/%s/instances/%s/databases/%s", projectId, instanceId, databaseId))
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	// First insert a couple of test records that we will delete using Partitioned DML.
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		return fmt.Errorf("failed to get a connection: %v", err)
+	}
+	if err := conn.Raw(func(driverConn interface{}) error {
+		_, err := driverConn.(spannerdriver.SpannerConn).Apply(ctx, []*spanner.Mutation{
+			spanner.InsertOrUpdateMap("Singers", map[string]interface{}{"SingerId": 1, "Name": "Singer 1"}),
+			spanner.InsertOrUpdateMap("Singers", map[string]interface{}{"SingerId": 2, "Name": "Singer 2"}),
+			spanner.InsertOrUpdateMap("Singers", map[string]interface{}{"SingerId": 3, "Name": "Singer 3"}),
+			spanner.InsertOrUpdateMap("Singers", map[string]interface{}{"SingerId": 4, "Name": "Singer 4"}),
+		})
+		return err
+	}); err != nil {
+		return fmt.Errorf("failed to insert test records: %v", err)
+	}
+
+	// Now delete all records in the Singers table using Partitioned DML.
+	if _, err := conn.ExecContext(ctx, "SET AUTOCOMMIT_DML_MODE='PARTITIONED_NON_ATOMIC'"); err != nil {
+		return fmt.Errorf("failed to change DML mode to Partitioned_Non_Atomic: %v", err)
+	}
+	res, err := conn.ExecContext(ctx, "DELETE FROM Singers WHERE TRUE")
+	if err != nil {
+		return fmt.Errorf("failed to execute DELETE statement: %v", err)
+	}
+	affected, err := res.RowsAffected()
+	if err != nil {
+		return fmt.Errorf("failed to get affected rows: %v", err)
+	}
+
+	// Partitioned DML returns the minimum number of records that were affected.
+	fmt.Printf("Deleted %v records using Partitioned DML\n", affected)
+
+	// Closing the connection will return it to the connection pool. The DML mode will automatically be reset to the
+	// default TRANSACTIONAL mode when the connection is returned to the pool, so we do not need to change it back
+	// manually.
+	_ = conn.Close()
+
+	return nil
+}
+
+func main() {
+	examples.RunSampleOnEmulator(partitionedDml, createTableStatement)
+}