Skip the second reranking for knowledge retrieval when there is only one dataset selected

[jzymx50]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

Currently when using knowledge retrieval node in a workflow, the multi-way retrieval is implemented even there is only one dataset, making an unneccessary second reranking. This would slow down the execution of workflow.

Suggestion: Skip the multi-way retrieval if there is only one dataset selected. Tips can be also added on frontend settings popup window.

2. Additional context or comments

No response

3. Can you help us with this feature?

• [x] I am interested in contributing to this feature.