FilterError in WeaviateDocumentStore

[vedantnaik19]

Describe the bug
A FilterError is raised when running a pipeline that includes a CacheChecker component and WeaviateDocumentStore.

raise FilterError(msg)
haystack.errors.FilterError: 'operator' key missing in {'file_path': 'filename.txt'}

To Reproduce
Steps to reproduce the behavior:

1. Set up WeaviateDocumentStore (in this case running locally at localhost:8080).
2. Create a pipeline with CacheChecker and WeaviateDocumentStore:

from haystack import Pipeline
from haystack.components.converters import TextFileToDocument
from haystack.components.writers import DocumentWriter
from haystack.components.caching import CacheChecker
from haystack_integrations.document_stores.weaviate import WeaviateDocumentStore

pipeline = Pipeline()
document_store = WeaviateDocumentStore(url="http:https://localhost:8080")
pipeline.add_component(instance=CacheChecker(document_store, cache_field="file_path"), name="cache_checker")
pipeline.add_component("converter", TextFileToDocument())
pipeline.add_component("writer", DocumentWriter(document_store))
pipeline.connect("cache_checker.misses", "converter.sources")
pipeline.connect("converter", "writer")
res = pipeline.run({"cache_checker": {"items": ["code_1.txt"]}})
print(res)

3. Run the script

Environment:

• OS: macOS 14.5, Apple M2 Pro
• Haystack version: 2.2.1
• Integration version: weaviate-haystack==2.1.0