community: fix issue with nested field extraction in MongodbLoader (#22801)
**Description:**
This PR addresses an issue in the `MongodbLoader` where nested fields
were not being correctly extracted. The loader now correctly handles
nested fields specified in the `field_names` parameter.
**Issue:**
Fixes an issue where attempting to extract nested fields from MongoDB
documents resulted in `KeyError`.
**Dependencies:**
No new dependencies are required for this change.
**Twitter handle:**
(Optional, your Twitter handle if you'd like a mention when the PR is
announced)
### Changes
1. **Field Name Parsing**:
- Added logic to parse nested field names and safely extract their
values from the MongoDB documents.
2. **Projection Construction**:
- Updated the projection dictionary to include nested fields correctly.
3. **Field Extraction**:
- Updated the `aload` method to handle nested field extraction using a
recursive approach to traverse the nested dictionaries.
### Example Usage
Updated usage example to demonstrate how to specify nested fields in the
`field_names` parameter:
```python
loader = MongodbLoader(
connection_string=MONGO_URI,
db_name=MONGO_DB,
collection_name=MONGO_COLLECTION,
filter_criteria={"data.job.company.industry_name": "IT", "data.job.detail": { "$exists": True }},
field_names=[
"data.job.detail.id",
"data.job.detail.position",
"data.job.detail.intro",
"data.job.detail.main_tasks",
"data.job.detail.requirements",
"data.job.detail.preferred_points",
"data.job.detail.benefits",
],
)
docs = loader.load()
print(len(docs))
for doc in docs:
print(doc.page_content)
```
### Testing
Tested with a MongoDB collection containing nested documents to ensure
that the nested fields are correctly extracted and concatenated into a
single page_content string.
### Note
This change ensures backward compatibility for non-nested fields and
improves functionality for nested field extraction.
### Output Sample
```python
print(docs[:3])
```
```shell
# output sample:
[
Document(
# Here in this example, page_content is the combined text from the fields below
# "position", "intro", "main_tasks", "requirements", "preferred_points", "benefits"
page_content='all combined contents from the requested fields in the document',
metadata={'database': 'Your Database name', 'collection': 'Your Collection name'}
),
...
]
```
---------
Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>
langchain
2b87e330 - community: fix issue with nested field extraction in MongodbLoader (#22801)
