dbutil: RewriteTable, generalize table.RewriteRows to copy from source table to destination table with row transformation

dbutil/rewrite.go

@@ -0,0 +1,37 @@
+// Copyright (C) 2017 ScyllaDB
+// Use of this source code is governed by a ALv2-style
+// license that can be found in the LICENSE file.
+
+package dbutil
+
+import (
+	"github.com/scylladb/gocqlx/v2"
+	"github.com/scylladb/gocqlx/v2/table"
+)
+
+// RewriteTable rewrites src table to dst table.
+// Rows can be transformed using the transform function.
+// Additional options can be passed to modify the insert query.
+func RewriteTable(session gocqlx.Session, dst, src *table.Table, transform func(map[string]interface{}), options ...func(q *gocqlx.Queryx)) error {
+	insert := dst.InsertQuery(session)
+	defer insert.Release()
+
+	// Apply query options
+	for _, o := range options {
+		o(insert)
+	}
+
+	// Iterate over all rows and reinsert them to dst table
+	iter := session.Query(src.SelectAll()).Iter()
+	m := make(map[string]interface{})
+	for iter.MapScan(m) {
+		if transform != nil {
+			transform(m)
+		}
+		if err := insert.BindMap(m).Exec(); err != nil {
+			return err
+		}
+		m = map[string]interface{}{}
+	}
+	return iter.Close()
+}