Optimize FindChangeInfosBetweenServerSeqs to prevent unnecessary Query

kokodak commented 3 weeks ago

What this PR does / why we need it:

This PR modifies the FindChangeInfosBetweenServerSeqs method to avoid executing DB queries when the from > to. This change minimizes unnecessary database resource consumption, particularly in scenarios where the most recent document editor, User A, continues editing without any interference from other users (B, C, etc.).

In such cases, in PushPull, User A's Checkpoint.serverSeq always equal to the server's initialServerSeq (DocInfo.serverSeq), leading to a situation where from > to in the FindChangeInfosBetweenServerSeqs method. By preventing the execution of a query under these circumstances, we can reduce the load on database resources.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

[x] Added relevant tests or not required
[x] Didn't break anything

Summary by CodeRabbit

Bug Fixes
- Improved error handling in the database query methods to prevent execution with invalid input parameters, enhancing overall stability and robustness.
Tests
- Added new test cases to validate the behavior of the database operations, ensuring consistent server sequence values during user editing without interference and verifying correct retrieval of document snapshots.

coderabbitai[bot] commented 3 weeks ago

Walkthrough

The recent changes introduce guard clauses in the FindChangeInfosBetweenServerSeqs methods within the Client and DB structs, ensuring that the methods return early if the from parameter exceeds the to parameter. Additionally, new test cases have been added to validate the behavior of these methods, enhancing test coverage and ensuring consistency in server sequence values.

Changes

File Path	Change Summary
`server/backend/database/mongo/client.go`	Added a guard clause in `FindChangeInfosBetweenServerSeqs` to return early if `from` > `to`, enhancing error handling.
`server/backend/database/memory/database.go`	Added a guard clause in `FindChangeInfosBetweenServerSeqs` to return early if `from` > `to`, enhancing error handling.
`server/backend/database/memory/database_test.go`	Introduced a new test case `RunFindChangeInfosBetweenServerSeqsTest` to validate behavior in database operations.
`server/backend/database/mongo/client_test.go`	Added a test case in `TestClient` for `RunFindChangeInfosBetweenServerSeqsTest`, verifying functionality.
`server/backend/database/testcases/testcases.go`	Added a new test function `RunFindChangeInfosBetweenServerSeqsTest` to check server sequence consistency.
`test/sharding/mongo_client_test.go`	Introduced a test case in `TestClientWithShardedDB` for `RunFindChangeInfosBetweenServerSeqsTest`, enhancing coverage.

Poem

🐇 In the code where sequences flow,
A guard now stands to help us know.
With checks in place, we leap with glee,
Avoiding errors, as safe as can be!
Hooray for changes, let them unfold,
A tale of robustness, brave and bold! 🌟

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codecov[bot] commented 3 weeks ago

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 51.14%. Comparing base (3f4f5d3) to head (1f7dbd3). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #974 +/- ## ========================================== + Coverage 51.06% 51.14% +0.07% ========================================== Files 73 73 Lines 10782 10788 +6 ========================================== + Hits 5506 5517 +11 + Misses 4725 4722 -3 + Partials 551 549 -2 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

kokodak commented 2 weeks ago

I've written test code to cover what was mentioned in the PR text. But I'm worried that the test case for the database has too business-like terms in it.

Also, I'm not sure how to express in the test that the from > to condition caused an early return. How do you think it should be expressed?

If you have any suggestions, please feel free to let me know.

sejongk commented 1 week ago

@hackerwins Would you mind reviewing all the changes?

kokodak commented 1 week ago

Could you explain me how to reproduce this scenario? I want to ensure there isn't another underlying issue.

Reproducing at the user level is very simple: you simply continue editing the document by yourself, without concurrent editing by other users.

Here is an example scenario:

A. Open the CodeMirror example of the JS SDK in a single browser B. Type 'abc' in the browser C. Check the server for queries from the corresponding editing client

In the above scenario, unnecessary queries were still occurring.

yorkie-team / yorkie