使用 Solr 数据导入处理程序将多值字段从 mySQL 导入 Solr

We have the following two tables in our mySQL:

mysql> describe comment;
+--------------+--------------+------+-----+---------+-------+
| Field        | Type         | Null | Key | Default | Extra |
+--------------+--------------+------+-----+---------+-------+
| id           | int(11)      | YES  |     | NULL    |       |
| blogpost_id  | int(11)      | YES  |     | NULL    |       |
| comment_text | varchar(256) | YES  |     | NULL    |       |
+--------------+--------------+------+-----+---------+-------+

mysql> describe comment_tags;
+------------+-------------+------+-----+---------+-------+
| Field      | Type        | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| comment_id | int(11)     | YES  |     | NULL    |       |
| tag        | varchar(80) | YES  |     | NULL    |       |
+------------+-------------+------+-----+---------+-------+

每个评论可以有多个标签.我们可以使用数据导入处理程序将整个注释导入 Solr.但是，我不确定如何将每个评论的标签导入为每个评论文档定义 schema.xml 的多值字段.

<dataConfig>
    <!-- dataSource is just an example. Included just for completeness. -->
    <dataSource batchSize="500" type="JdbcDataSource" driver="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost/my-database" user="root" password="somethinglong1283"/>
<document>
    <entity name="comment" pk="id" query="SELECT * FROM comment">
        <field column="blogpost_id" name="blogpost_id"/>
        <field column="comment_text" name="comment_text" />
        <entity name="comment_tags" pk="comment_id" query="SELECT * FROM comment_tags WHERE comment_id='${comment.id}'">
            <field column="tag" name="tag" />
        </entity>
    </entity>
</document>