search through all collections of a database in Mongodb (python) - mongodb

Question

How to search all the collections of a database-name: test for a word having length say 6
The sample data in collections is like:
{
"_id": {
"$oid": "5e0983863bcf0dab51f2872b"
},
"word": "never",
"wordset_id": "a42b50e85e",
"meanings": [{
"id": "1f1bca9d9f",
"def": "not ever",
"speech_part": "adverb",
"synonyms": ["ne'er"]
}, {
"id": "d35f973ed0",
"def": "not at all",
"speech_part": "adverb"
}]
}
How can I query for all words with length of 6 across all collections of test?
I have tried this way but it is giving only first collection results:
#app.......
def fn():
collections=db.collection_names()
for collection in collections:
data = db[collection].aggregate([
{
"$match": {
"$expr": {"$eq": [{"$strLenCP": "$word"}, n]}
}
}
])
return render_template('lettersearch.html',data=data)
when I am printing data I get all cursors as:
<pymongo.command_cursor.CommandCursor object at 0x00000258F4F5B470>
<pymongo.command_cursor.CommandCursor object at 0x00000258F4F76BA8>
<pymongo.command_cursor.CommandCursor object at 0x00000258F4F6E5F8>
<pymongo.command_cursor.CommandCursor object at 0x00000258F4F8A6A0>
<pymongo.command_cursor.CommandCursor object at 0x00000258F4F8E048>
How to iterate over these objects and render in template as data?

Answer 1

How to search all the collections of a database
You can achieve this in two steps:
Retrieve all collections in the database - db.getCollectionNames()
For each collection run the query below
Query:
db.collection.aggregate([
{
$match: {
$expr: {
$eq: [
{
$strLenCP: "$word"
},
6
]
}
}
}
]);

Answer 2

For each collection use $strLenCP with this aggregation:
db.collection.aggregate([
{
$match: {
$expr: {$eq: [{$strLenCP: "$word"}, 6]}
}
}
])