Fixed an issue with orderless fields in firestore indexes

[joehan]

Description

Fixes #8910 - turns out some indexes don't have orders, so we need to look at the last index with an order when filtering.

I had Gemini work on this one, but the solution looks correct to me.

[gemini-code-assist]

Summary of Changes

Hello @joehan, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a bug in how Firestore indexes are processed, specifically when dealing with __name__ fields that might follow fields without explicit ordering, such as vector fields. The core change ensures that the correct default direction for these __name__ fields is determined by looking for the last ordered field in the index, preventing incorrect filtering and improving the accuracy of index processing.

Highlights

• Firestore Index Processing Logic: I've updated the FirestoreApi.processIndexes method to correctly handle Firestore indexes where fields might not have an explicit order, such as vector fields. This ensures that the __name__ field is properly filtered based on the last ordered field in the index.
• New Test Case for Index Filtering: I've added a new test case in src/firestore/indexes.spec.ts to validate the fix, specifically ensuring that __name__ fields are correctly filtered out when the preceding field is a vector field.

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[gemini-code-assist]

Code Review

The pull request correctly addresses an issue where Firestore indexes with orderless fields (like vector fields) were not handled properly when filtering implicit __name__ fields. The logic is now more robust, searching for the last field that actually has an order. The addition of a new test case for this specific scenario is great. I've added one suggestion to improve the performance of the new logic by avoiding unnecessary array creation and reversal.

[gemini-code-assist]

While this implementation is correct, it can be made more efficient by avoiding the creation of a new reversed array for each index. A simple for loop iterating backwards would be more performant and avoid unnecessary memory allocation, especially for indexes with many fields.

        let defaultDirection: types.Order | undefined;
        // Find the last field with an order, iterating backwards from the second to last field.
        for (let i = fields.length - 2; i >= 0; i--) {
          if (fields[i].order) {
            defaultDirection = fields[i].order;
            break;
          }
        }

[codecov-commenter]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 50.68%. Comparing base (f1c2d21) to head (467d7c2).
⚠️ Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
src/firestore/api.ts	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8913      +/-   ##
==========================================
- Coverage   52.18%   50.68%   -1.50%     
==========================================
  Files         418      496      +78     
  Lines       30694    32880    +2186     
  Branches     6348     6831     +483     
==========================================
+ Hits        16018    16666     +648     
- Misses      13234    14746    +1512     
- Partials     1442     1468      +26     

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[aalej]

It seems like the issue is still occurring

$ firebase deploy --only firestore --project PROJECT_ID
=== Deploying to 'PROJECT_ID'...

i  deploying firestore
i  firestore: reading indexes from firestore.indexes.json...
i  cloud.firestore: checking firestore.rules for compilation errors...
✔  cloud.firestore: rules file firestore.rules compiled successfully
i  firestore: uploading rules firestore.rules...
i  firestore: deploying indexes...
i  firestore: The following indexes are defined in your project but are not present in your firestore indexes file:
        (collection10) -- (field4,VECTOR<1536>) 
        (collection10) -- (field1,ASCENDING) (field2,ASCENDING) (field3,ASCENDING) (field4,VECTOR<1536>) 
        (collection10) -- (field5,ASCENDING) (field4,VECTOR<1536>) 
✔ Would you like to delete these indexes? Selecting no will continue the rest of the deployment. No

Error: Request to https://firestore.googleapis.com/v1/projects/PROJECT_ID/databases/(default)/collectionGroups/collection10/indexes had HTTP Error: 409, index already exists