Solr DIH: documents are not nested - solr

Question

I'm trying to import some data as nested documents.
I've tried to simplify my problem as much as possible.
Here my parent query:
SELECT 1 AS id,
'xxx' AS col1,
'yyy' AS col2
UNION
SELECT 2 AS id,
'xxx' AS col1,
'yyy' AS col2
UNION
SELECT 3 AS id,
'xxx' AS col1,
'yyy' AS col2
You can see data here:
1 | xxx | yyy
2 | xxx | yyy
3 | xxx | yyy
My child query is:
SELECT 1 AS id,
1 AS rel_id,
'aaa' AS col1,
'bbb' AS col2
UNION
SELECT 2 AS id,
1 AS rel_id,
'aaa' AS col1,
'bbb' AS col2
UNION
SELECT 3 AS id,
2 AS rel_id,
'aaa' AS col1,
'bbb' AS col2
UNION
SELECT 4 AS id,
3 AS rel_id,
'aaa' AS col1,
'bbb' AS col2
Data is:
1 | 1 | aaa | bbb
2 | 1 | aaa | bbb
3 | 2 | aaa | bbb
4 | 3 | aaa | bbb
I'm trying to nest using this DIH configuration:
<entity
name="item"
query="select 1 as id, 'xxx' as col1, 'yyy' as col2 union select 2 as id, 'xxx' as col1, 'yyy' as col2 union select 3 as id, 'xxx' as col1, 'yyy' as col2">
<field column="id" name="id"/>
<field column="col1" name="column1_s" />
<field column="col2" name="column2_s" />
<entity
name="autor"
child="true"
query="select 1 as id, 1 as rel_id, 'aaa' as col1, 'bbb' as col2 union select 2 as id, 1 as rel_id, 'aaa' as col1, 'bbb' as col2 union select 3 as id, 2 as rel_id, 'aaa' as col1, 'bbb' as col2 union select 4 as id, 3 as rel_id, 'aaa' as col1, 'bbb' as col2"
cacheKey="rel_id" cacheLookup="item.id" cacheImpl="SortedMapBackedCache">
<field column="node_type" template="autor"/>
<field column="alt_code" name="id" template="${autor.id}-${autor.rel_id}"/>
<field column="col1" name="column1_s" />
<field column="col2" name="column2_s" />
</entity>
</entity>
However, they are not nested:
$ curl "http://localhost:8983/solr/arxius/select?q=*%3A*"
{
"responseHeader": {
"status": 0,
"QTime": 0,
"params": {
"q": "*:*"
}
},
"response": {
"numFound": 7,
"start": 0,
"numFoundExact": true,
"docs": [
{
"id": "1",
"column2_s": "bbb",
"column1_s": "aaa",
"_version_": 1682901366056419300
},
{
"id": "2",
"column2_s": "bbb",
"column1_s": "aaa",
"_version_": 1682901366056419300
},
{
"id": "1",
"column2_s": "yyy",
"column1_s": "xxx",
"_version_": 1682901366056419300
},
{
"id": "3",
"column2_s": "bbb",
"column1_s": "aaa",
"_version_": 1682901366058516500
},
{
"id": "2",
"column2_s": "yyy",
"column1_s": "xxx",
"_version_": 1682901366058516500
},
{
"id": "4",
"column2_s": "bbb",
"column1_s": "aaa",
"_version_": 1682901366058516500
},
{
"id": "3",
"column2_s": "yyy",
"column1_s": "xxx",
"_version_": 1682901366058516500
}
]
}
}
As you can see, documents are not nested.
I've been struggling a lot over that issue.
I've tried to strightforward the problem.
I hope I've explained so well.
Please, any ideas?