feat: add toBuilder() method to Statement

google-cloud-spanner/src/main/java/com/google/cloud/spanner/Statement.java

@@ -68,16 +68,24 @@ private Statement(String sql, ImmutableMap<String, Value> parameters, QueryOptio
 
   /** Builder for {@code Statement}. */
   public static final class Builder {
-    final Map<String, Value> parameters = new HashMap<>();
+    final Map<String, Value> parameters;
     private final StringBuilder sqlBuffer;
     private String currentBinding;
     private final ValueBinder<Builder> binder = new Binder();
     private QueryOptions queryOptions;
 
     private Builder(String sql) {
+      parameters = new HashMap<>();
       sqlBuffer = new StringBuilder(sql);
     }
 
+    private Builder(Statement statement) {
+      sqlBuffer = new StringBuilder(statement.sql);
+      parameters = new HashMap<>(statement.parameters);
+      queryOptions =
+          statement.queryOptions == null ? null : statement.queryOptions.toBuilder().build();
+    }
+
     /** Appends {@code sqlFragment} to the statement. */
     public Builder append(String sqlFragment) {
       sqlBuffer.append(checkNotNull(sqlFragment));
@@ -171,6 +179,10 @@ public Map<String, Value> getParameters() {
     return parameters;
   }
 
+  public Builder toBuilder() {
+    return new Builder(this);
+  }
+
   @Override
   public String toString() {
     return toString(new StringBuilder()).toString();