Add Spanner dialect to pkg/storage/unified/sql/sqltemplate package. (#102121)

pkg/storage/unified/sql/sqltemplate/dialect.go

@@ -24,6 +24,8 @@ func DialectForDriver(driverName string) Dialect {
 		return PostgreSQL
 	case "sqlite", "sqlite3":
 		return SQLite
+	case "spanner":
+		return Spanner
 	default:
 		return nil
 	}

pkg/storage/unified/sql/sqltemplate/dialect_spanner.go

@@ -0,0 +1,32 @@
+package sqltemplate
+
+// Spanner is an implementation of Dialect for the Google Spanner database.
+var Spanner = spanner{}
+
+var _ Dialect = Spanner
+
+type spanner struct{}
+
+func (s spanner) DialectName() string {
+	return "spanner"
+}
+
+func (s spanner) Ident(a string) (string, error) {
+	return backtickIdent{}.Ident(a)
+}
+
+func (s spanner) ArgPlaceholder(argNum int) string {
+	return argFmtSQL92.ArgPlaceholder(argNum)
+}
+
+func (s spanner) SelectFor(a ...string) (string, error) {
+	return rowLockingClauseSpanner.SelectFor(a...)
+}
+
+func (spanner) CurrentEpoch() string {
+	return "UNIX_MICROS(CURRENT_TIMESTAMP())"
+}
+
+var rowLockingClauseSpanner = rowLockingClauseMap{
+	SelectForUpdate: SelectForUpdate,
+}