fix: selecting search all doesnt work

[varunsharma27]

Description

• Please include a summary of the changes and the related issue.
• Fixes [BUG] Selecting 'Search All' doesn't work. #626
• Fixes [BUG] LightRAG file selection #561 adding new documents should update the existing index within the file collection instead of creating new one

Further info on the bug (#561):

Each time you upload files, will create a unique id, then create a folder by id, and store light rag data in this folder.

Drag & Drop each file separately to LightRag file collection causes them to be separated

1. Two separate indexes are created under ktem_app_data\user_data\files\lightrag\
2. Query will only search against one index at a time even if both files are selected. And "Search All" button doesn't work. It will complaint no documents are selected.
3. When selecting multiple files in the drop down, only the first one selected will be included in the search. The others will be ignored.

Drag & Drop both (all) files at the same time to be indexed

1. One index is created under ktem_app_data\user_data\files\lightrag\
2. Query will search both documents
3. Query will search both documents EVEN if I only selected one file in the drop down.

Solution

Adding new documents should update the existing index within the file collection instead of creating new one. Which is implemented in this PR.

Type of change

• New features (non-breaking change).
• Bug fix (non-breaking change).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).

Checklist

• I have performed a self-review of my code.
• I have added thorough tests if it is a core feature.
• There is a reference to the original bug report and related work.
• I have commented on my code, particularly in hard-to-understand areas.
• The feature is well documented.

[Silverls96]

assert (
            len(self.file_ids) <= 1
        ), "GraphRAG retriever only supports one file_id at a time"

        file_id = self.file_ids[0]

    I wonder is it because of this?

[varunsharma27]

@Silverls96 Thats interesting, this error is only present in the GraphRAG whereas LightRAG just picks the first file of the bunch.

I think it's because of lack of incremental graph updates in GraphRAG so the file collection can be disjoint in terms of graphs.

[Silverls96]

@varunsharma27 yeah. I think we need to have an option certain group "A" of files will update index when new files added or something alike. We don't always use the same index. It will be nice to have that.