feat: support default isolation level for connection

conn.go

@@ -114,6 +114,13 @@ type SpannerConn interface {
 	// mode and for read-only transaction.
 	SetReadOnlyStaleness(staleness spanner.TimestampBound) error
 
+	// IsolationLevel returns the current default isolation level that is
+	// used for read/write transactions on this connection.
+	IsolationLevel() sql.IsolationLevel
+	// SetIsolationLevel sets the default isolation level to use for read/write
+	// transactions on this connection.
+	SetIsolationLevel(level sql.IsolationLevel) error
+
 	// TransactionTag returns the transaction tag that will be applied to the next
 	// read/write transaction on this connection. The transaction tag that is set
 	// on the connection is cleared when a read/write transaction is started.
@@ -235,6 +242,10 @@ type conn struct {
 	autocommitDMLMode AutocommitDMLMode
 	// readOnlyStaleness is used for queries in autocommit mode and for read-only transactions.
 	readOnlyStaleness spanner.TimestampBound
+	// isolationLevel determines the default isolation level that is used for read/write
+	// transactions on this connection. This default is ignored if the BeginTx function is
+	// called with an isolation level other than sql.LevelDefault.
+	isolationLevel sql.IsolationLevel
 
 	// execOptions are applied to the next statement or transaction that is executed
 	// on this connection. It can also be set by passing it in as an argument to
@@ -309,6 +320,15 @@ func (c *conn) setReadOnlyStaleness(staleness spanner.TimestampBound) (driver.Re
 	return driver.ResultNoRows, nil
 }
 
+func (c *conn) IsolationLevel() sql.IsolationLevel {
+	return c.isolationLevel
+}
+
+func (c *conn) SetIsolationLevel(level sql.IsolationLevel) error {
+	c.isolationLevel = level
+	return nil
+}
+
 func (c *conn) MaxCommitDelay() time.Duration {
 	return *c.execOptions.TransactionOptions.CommitOptions.MaxCommitDelay
 }
@@ -633,6 +653,7 @@ func (c *conn) ResetSession(_ context.Context) error {
 	c.autoBatchDmlUpdateCount = c.connector.connectorConfig.AutoBatchDmlUpdateCount
 	c.autoBatchDmlUpdateCountVerification = !c.connector.connectorConfig.DisableAutoBatchDmlUpdateCountVerification
 	c.retryAborts = c.connector.retryAbortsInternally
+	c.isolationLevel = c.connector.connectorConfig.IsolationLevel
 	// TODO: Reset the following fields to the connector default
 	c.autocommitDMLMode = Transactional
 	c.readOnlyStaleness = spanner.TimestampBound{}
@@ -888,10 +909,20 @@ func (c *conn) getTransactionOptions() ReadWriteTransactionOptions {
 	defer func() {
 		c.execOptions.TransactionOptions.TransactionTag = ""
 	}()
-	return ReadWriteTransactionOptions{
+	txOpts := ReadWriteTransactionOptions{
 		TransactionOptions:     c.execOptions.TransactionOptions,
 		DisableInternalRetries: !c.retryAborts,
 	}
+	// Only use the default isolation level from the connection if the ExecOptions
+	// did not contain a more specific isolation level.
+	if txOpts.TransactionOptions.IsolationLevel == spannerpb.TransactionOptions_ISOLATION_LEVEL_UNSPECIFIED {
+		// This should never really return an error, but we check just to be absolutely sure.
+		level, err := toProtoIsolationLevel(c.isolationLevel)
+		if err == nil {
+			txOpts.TransactionOptions.IsolationLevel = level
+		}
+	}
+	return txOpts
 }
 
 func (c *conn) withTempReadOnlyTransactionOptions(options *ReadOnlyTransactionOptions) {

conn_with_mockserver_test.go

@@ -17,9 +17,11 @@ package spannerdriver
 import (
 	"context"
 	"database/sql"
+	"fmt"
 	"reflect"
 	"testing"
 
+	"cloud.google.com/go/spanner"
 	"cloud.google.com/go/spanner/apiv1/spannerpb"
 	"github.com/googleapis/go-sql-spanner/testutil"
 )
@@ -115,3 +117,125 @@ func TestBeginTxWithInvalidIsolationLevel(t *testing.T) {
 		}
 	}
 }
+
+func TestDefaultIsolationLevel(t *testing.T) {
+	t.Parallel()
+
+	for _, level := range []sql.IsolationLevel{
+		sql.LevelDefault,
+		sql.LevelSnapshot,
+		sql.LevelRepeatableRead,
+		sql.LevelSerializable,
+	} {
+		db, server, teardown := setupTestDBConnectionWithParams(t, fmt.Sprintf("isolationLevel=%v", level))
+		defer teardown()
+		ctx := context.Background()
+
+		conn, err := db.Conn(ctx)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := conn.Raw(func(driverConn interface{}) error {
+			spannerConn, ok := driverConn.(SpannerConn)
+			if !ok {
+				return fmt.Errorf("expected spanner conn, got %T", driverConn)
+			}
+			if spannerConn.IsolationLevel() != level {
+				return fmt.Errorf("expected isolation level %v, got %v", level, spannerConn.IsolationLevel())
+			}
+			return nil
+		}); err != nil {
+			t.Fatal(err)
+		}
+
+		originalLevel := level
+		for _, disableRetryAborts := range []bool{true, false} {
+			if disableRetryAborts {
+				level = WithDisableRetryAborts(originalLevel)
+			} else {
+				level = originalLevel
+			}
+			// Note: No isolation level is passed in here, so it will use the default.
+			tx, _ := db.BeginTx(ctx, &sql.TxOptions{})
+			_, _ = tx.ExecContext(ctx, testutil.UpdateBarSetFoo)
+			_ = tx.Rollback()
+
+			requests := drainRequestsFromServer(server.TestSpanner)
+			beginRequests := requestsOfType(requests, reflect.TypeOf(&spannerpb.BeginTransactionRequest{}))
+			if g, w := len(beginRequests), 1; g != w {
+				t.Fatalf("begin requests count mismatch\n Got: %v\nWant: %v", g, w)
+			}
+			request := beginRequests[0].(*spannerpb.BeginTransactionRequest)
+			wantIsolationLevel, _ := toProtoIsolationLevel(originalLevel)
+			if g, w := request.Options.GetIsolationLevel(), wantIsolationLevel; g != w {
+				t.Fatalf("begin isolation level mismatch\n Got: %v\nWant: %v", g, w)
+			}
+		}
+	}
+}
+
+func TestSetIsolationLevel(t *testing.T) {
+	t.Parallel()
+
+	db, _, teardown := setupTestDBConnection(t)
+	defer teardown()
+	ctx := context.Background()
+
+	// Repeat twice to ensure that the state is reset after closing the connection.
+	for i := 0; i < 2; i++ {
+		conn, err := db.Conn(ctx)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var level sql.IsolationLevel
+		_ = conn.Raw(func(driverConn interface{}) error {
+			level = driverConn.(SpannerConn).IsolationLevel()
+			return nil
+		})
+		if g, w := level, sql.LevelDefault; g != w {
+			t.Fatalf("isolation level mismatch\n Got: %v\nWant: %v", g, w)
+		}
+		_ = conn.Raw(func(driverConn interface{}) error {
+			return driverConn.(SpannerConn).SetIsolationLevel(sql.LevelSnapshot)
+		})
+		_ = conn.Raw(func(driverConn interface{}) error {
+			level = driverConn.(SpannerConn).IsolationLevel()
+			return nil
+		})
+		if g, w := level, sql.LevelSnapshot; g != w {
+			t.Fatalf("isolation level mismatch\n Got: %v\nWant: %v", g, w)
+		}
+		conn.Close()
+	}
+}
+
+func TestIsolationLevelAutoCommit(t *testing.T) {
+	t.Parallel()
+
+	db, server, teardown := setupTestDBConnection(t)
+	defer teardown()
+	ctx := context.Background()
+
+	for _, level := range []sql.IsolationLevel{
+		sql.LevelDefault,
+		sql.LevelSnapshot,
+		sql.LevelRepeatableRead,
+		sql.LevelSerializable,
+	} {
+		spannerLevel, _ := toProtoIsolationLevel(level)
+		_, _ = db.ExecContext(ctx, testutil.UpdateBarSetFoo, ExecOptions{TransactionOptions: spanner.TransactionOptions{
+			IsolationLevel: spannerLevel,
+		}})
+
+		requests := drainRequestsFromServer(server.TestSpanner)
+		executeRequests := requestsOfType(requests, reflect.TypeOf(&spannerpb.ExecuteSqlRequest{}))
+		if g, w := len(executeRequests), 1; g != w {
+			t.Fatalf("execute requests count mismatch\n Got: %v\nWant: %v", g, w)
+		}
+		request := executeRequests[0].(*spannerpb.ExecuteSqlRequest)
+		wantIsolationLevel, _ := toProtoIsolationLevel(level)
+		if g, w := request.Transaction.GetBegin().GetIsolationLevel(), wantIsolationLevel; g != w {
+			t.Fatalf("begin isolation level mismatch\n Got: %v\nWant: %v", g, w)
+		}
+	}
+}

driver.go

@@ -231,6 +231,9 @@ type ConnectorConfig struct {
 	AutoBatchDmlUpdateCount                    int64
 	DisableAutoBatchDmlUpdateCountVerification bool
 
+	// IsolationLevel is the default isolation level for read/write transactions.
+	IsolationLevel sql.IsolationLevel
+
 	// DecodeToNativeArrays determines whether arrays that have a Go native
 	// type should be decoded to those types rather than the corresponding
 	// spanner.NullTypeName type.
@@ -472,6 +475,11 @@ func createConnector(d *Driver, connectorConfig ConnectorConfig) (*connector, er
 			connectorConfig.AutoConfigEmulator = val
 		}
 	}
+	if strval, ok := connectorConfig.Params[strings.ToLower("IsolationLevel")]; ok {
+		if val, err := parseIsolationLevel(strval); err == nil {
+			connectorConfig.IsolationLevel = val
+		}
+	}
 
 	// Check if it is Spanner gorm that is creating the connection.
 	// If so, we should set a different user-agent header than the
@@ -1058,6 +1066,28 @@ func checkIsValidType(v driver.Value) bool {
 	return true
 }
 
+func parseIsolationLevel(val string) (sql.IsolationLevel, error) {
+	switch strings.Replace(strings.ToLower(strings.TrimSpace(val)), " ", "_", 1) {
+	case "default":
+		return sql.LevelDefault, nil
+	case "read_uncommitted":
+		return sql.LevelReadUncommitted, nil
+	case "read_committed":
+		return sql.LevelReadCommitted, nil
+	case "write_committed":
+		return sql.LevelWriteCommitted, nil
+	case "repeatable_read":
+		return sql.LevelRepeatableRead, nil
+	case "snapshot":
+		return sql.LevelSnapshot, nil
+	case "serializable":
+		return sql.LevelSerializable, nil
+	case "linearizable":
+		return sql.LevelLinearizable, nil
+	}
+	return sql.LevelDefault, spanner.ToSpannerError(status.Errorf(codes.InvalidArgument, "invalid or unsupported isolation level: %v", val))
+}
+
 func toProtoIsolationLevel(level sql.IsolationLevel) (spannerpb.TransactionOptions_IsolationLevel, error) {
 	switch level {
 	case sql.LevelSerializable:

driver_test.go

@@ -160,6 +160,21 @@ func TestExtractDnsParts(t *testing.T) {
 				DisableNativeMetrics: true,
 			},
 		},
+		{
+			input: "projects/p/instances/i/databases/d?isolationLevel=repeatable_read;",
+			wantConnectorConfig: ConnectorConfig{
+				Project:  "p",
+				Instance: "i",
+				Database: "d",
+				Params: map[string]string{
+					"isolationlevel": "repeatable_read",
+				},
+			},
+			wantSpannerConfig: spanner.ClientConfig{
+				SessionPoolConfig: spanner.DefaultSessionPoolConfig,
+				UserAgent:         userAgent,
+			},
+		},
 		{
 			input: "spanner.googleapis.com/projects/p/instances/i/databases/d?minSessions=200;maxSessions=1000;numChannels=10;disableRouteToLeader=true;enableEndToEndTracing=true;disableNativeMetrics=true;rpcPriority=Medium;optimizerVersion=1;optimizerStatisticsPackage=latest;databaseRole=child",
 			wantConnectorConfig: ConnectorConfig{
@@ -291,6 +306,77 @@ func TestToProtoIsolationLevel(t *testing.T) {
 	}
 }
 
+func TestParseIsolationLevel(t *testing.T) {
+	tests := []struct {
+		input   string
+		want    sql.IsolationLevel
+		wantErr bool
+	}{
+		{
+			input: "default",
+			want:  sql.LevelDefault,
+		},
+		{
+			input: " DEFAULT   ",
+			want:  sql.LevelDefault,
+		},
+		{
+			input: "read uncommitted",
+			want:  sql.LevelReadUncommitted,
+		},
+		{
+			input: "  read_uncommitted\n",
+			want:  sql.LevelReadUncommitted,
+		},
+		{
+			input: "read committed",
+			want:  sql.LevelReadCommitted,
+		},
+		{
+			input: "write committed",
+			want:  sql.LevelWriteCommitted,
+		},
+		{
+			input: "repeatable read",
+			want:  sql.LevelRepeatableRead,
+		},
+		{
+			input: "snapshot",
+			want:  sql.LevelSnapshot,
+		},
+		{
+			input: "serializable",
+			want:  sql.LevelSerializable,
+		},
+		{
+			input: "linearizable",
+			want:  sql.LevelLinearizable,
+		},
+		{
+			input:   "read serializable",
+			wantErr: true,
+		},
+		{
+			input:   "",
+			wantErr: true,
+		},
+		{
+			input:   "read-committed",
+			wantErr: true,
+		},
+	}
+	for _, tc := range tests {
+		level, err := parseIsolationLevel(tc.input)
+		if tc.wantErr && err == nil {
+			t.Errorf("parseIsolationLevel(%q): expected error", tc.input)
+		} else if !tc.wantErr && err != nil {
+			t.Errorf("parseIsolationLevel(%q): unexpected error: %v", tc.input, err)
+		} else if level != tc.want {
+			t.Errorf("parseIsolationLevel(%q): got %v, want %v", tc.input, level, tc.want)
+		}
+	}
+}
+
 func ExampleCreateConnector() {
 	connectorConfig := ConnectorConfig{
 		Project:  "my-project",