google-research/perch-hoplite

Investigate better threading in SQLIteUsearchImpl

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#127 opened on May 12, 2026

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good first issue

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Description

Currently, we make a thread_split copy of the DB for each thread. Phil points out that we might be able to use the thread-local cursor instead, and save a whole pile of overhead.

From Phil's modified SQLiteUsearchImpl:

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # Create a thread-local storage container
        self._thread_local = threading.local()


    def _get_cursor(self) -> sqlite3.Cursor:
        """
        Override: Returns a thread-local cursor. 
        If the current thread doesn't have one, it creates it.
        """
        if not hasattr(self._thread_local, 'cursor'):
            self._thread_local.cursor = self.db.cursor()
        return self._thread_local.cursor

Contributor guide

Research direction
Implement thread local cursor and benchmark against current thread split approach.
Tech stack
python
Domain
backenddatabase
Issue type
Performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
PythonThreadingSQLite
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60