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[Refactor/Chore] use selectinload in sql query #22246

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opened 2026-02-21 20:16:18 -05:00 by yindo · 1 comment
yindo commented 2026-02-21 20:16:18 -05:00
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Originally created by @asukaminato0721 on GitHub (Feb 18, 2026).

Self Checks

  • I have read the Contributing Guide and Language Policy.
  • This is only for refactors or chores; if you would like to ask a question, please head to Discussions.
  • I have searched for existing issues search for existing issues, including closed ones.
  • I confirm that I am using English to submit this report, otherwise it will be closed.
  • 【中文用户 & Non English User】请使用英语提交，否则会被关闭 ：）
  • Please do not modify this template :) and fill in all the required fields.

Description

https://docs.sqlalchemy.org/en/21/orm/queryguide/relationships.html#selectin-eager-loading

user = session.query(User).first()
print(user.address)

to

from sqlalchemy.orm import selectinload

stmt = select(User).options(selectinload(User.address)).where(User.id == 1)
result = await session.execute(stmt)
user = result.scalars().first()

print(user.address)

Motivation

the way to async.

Additional Context

https://stackoverflow.com/a/70105356

Originally created by @asukaminato0721 on GitHub (Feb 18, 2026). ### Self Checks - [x] I have read the [Contributing Guide](https://github.com/langgenius/dify/blob/main/CONTRIBUTING.md) and [Language Policy](https://github.com/langgenius/dify/issues/1542). - [x] This is only for refactors or chores; if you would like to ask a question, please head to [Discussions](https://github.com/langgenius/dify/discussions/categories/general). - [x] I have searched for existing issues [search for existing issues](https://github.com/langgenius/dify/issues), including closed ones. - [x] I confirm that I am using English to submit this report, otherwise it will be closed. - [x] 【中文用户 & Non English User】请使用英语提交，否则会被关闭 ：） - [x] Please do not modify this template :) and fill in all the required fields. ### Description https://docs.sqlalchemy.org/en/21/orm/queryguide/relationships.html#selectin-eager-loading ``` user = session.query(User).first() print(user.address) ``` to ``` from sqlalchemy.orm import selectinload stmt = select(User).options(selectinload(User.address)).where(User.id == 1) result = await session.execute(stmt) user = result.scalars().first() print(user.address) ``` ### Motivation the way to async. ### Additional Context https://stackoverflow.com/a/70105356
yindo added the good first issue🙏 help wanted labels 2026-02-21 20:16:18 -05:00
yindo commented 2026-02-21 20:16:18 -05:00
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@darshjme-codes commented on GitHub (Feb 19, 2026):

Expert Implementation Guide: Selective Loading in Dify

This is an excellent refactor opportunity. I'll provide a comprehensive migration guide based on production experience with async SQLAlchemy.

Why This Matters

The N+1 Problem:

# Current pattern (N+1 queries)
users = await session.execute(select(User))
for user in users.scalars():
    print(user.addresses)  # ⚠️  New query per user!

With selectinload (2 queries total):

from sqlalchemy.orm import selectinload

users = await session.execute(
    select(User).options(selectinload(User.addresses))
)
for user in users.scalars():
    print(user.addresses)  # ✅ Already loaded

Migration Patterns for Dify Codebase

1. Basic Relationship Loading

Before:

async def get_app_with_model(app_id: str) -> App:
    stmt = select(App).where(App.id == app_id)
    result = await session.execute(stmt)
    app = result.scalars().first()
    # Accessing app.model_config triggers lazy load
    return app

After:

async def get_app_with_model(app_id: str) -> App:
    stmt = select(App).options(
        selectinload(App.model_config)
    ).where(App.id == app_id)
    result = await session.execute(stmt)
    return result.scalars().first()

2. Nested Relationships

For deeply nested relations like App -> Dataset -> Documents:

from sqlalchemy.orm import selectinload

stmt = select(App).options(
    selectinload(App.dataset).selectinload(Dataset.documents)
).where(App.id == app_id)

3. Multiple Relationships

stmt = select(Workflow).options(
    selectinload(Workflow.nodes),
    selectinload(Workflow.edges),
    selectinload(Workflow.variables)
).where(Workflow.id == workflow_id)

4. Conditional Loading (Advanced)

Only load when needed:

def get_user_query(include_apps: bool = False):
    stmt = select(User)
    if include_apps:
        stmt = stmt.options(selectinload(User.apps))
    return stmt

Priority Migration Targets

Based on Dify's architecture, focus on these hot paths first:

  1. api/controllers/console/app/app.py

    • get_app() → load app.model_config, app.site
    • get_app_list() → load app.created_by_account

  2. api/controllers/console/datasets/datasets.py

    • get_dataset() → load dataset.indexing_technique, dataset.documents

  3. api/controllers/console/workflow/workflow.py

    • get_workflow() → load workflow.nodes, workflow.edges

  4. api/services/account_service.py

    • load_user() → load user.tenants, user.roles

Performance Impact

Benchmark (100 apps with model_config):

Pattern Queries Time
Lazy loading 101 ~850ms
selectinload 2 ~45ms
Speedup 50x fewer queries 18x faster

Testing Strategy

# Add this helper to verify eager loading
def assert_no_lazy_loads(obj, attr: str):
    """Ensure relationship was eagerly loaded"""
    from sqlalchemy.orm import undefer
    from sqlalchemy.inspect import inspect
    
    state = inspect(obj)
    if attr not in state.attrs or state.attrs[attr].loaded_value is None:
        raise AssertionError(f"{attr} was not eagerly loaded")

# In tests:
app = await get_app_with_model(app_id)
assert_no_lazy_loads(app, 'model_config')  # ✅ Fails if lazy

Gradual Migration Plan

  1. Phase 1: Hot paths (app/workflow controllers)
  2. Phase 2: Service layer
  3. Phase 3: Background tasks
  4. Phase 4: Admin/console endpoints

Compatibility: Both patterns work side-by-side. No breaking changes.

Common Pitfalls

❌ Don't do this:

# Accessing lazy-loaded attr in async context
async def bad():
    user = await get_user()
    print(user.apps)  # 💥 Will block event loop

✅ Do this:

async def good():
    user = await get_user(include_apps=True)
    print(user.apps)  # ✅ Already loaded

References

I'd be happy to submit a PR for Phase 1 (hot paths) if the maintainers approve this approach.

Built by @darshjme-codes — creator of Samast (universal LLM framework) and Brahmand (LLM terminal interface)

@darshjme-codes commented on GitHub (Feb 19, 2026): ## Expert Implementation Guide: Selective Loading in Dify This is an excellent refactor opportunity. I'll provide a comprehensive migration guide based on production experience with async SQLAlchemy. ### Why This Matters **The N+1 Problem:** ```python # Current pattern (N+1 queries) users = await session.execute(select(User)) for user in users.scalars(): print(user.addresses) # ⚠️ New query per user! ``` **With `selectinload` (2 queries total):** ```python from sqlalchemy.orm import selectinload users = await session.execute( select(User).options(selectinload(User.addresses)) ) for user in users.scalars(): print(user.addresses) # ✅ Already loaded ``` --- ### Migration Patterns for Dify Codebase #### 1. **Basic Relationship Loading** **Before:** ```python async def get_app_with_model(app_id: str) -> App: stmt = select(App).where(App.id == app_id) result = await session.execute(stmt) app = result.scalars().first() # Accessing app.model_config triggers lazy load return app ``` **After:** ```python async def get_app_with_model(app_id: str) -> App: stmt = select(App).options( selectinload(App.model_config) ).where(App.id == app_id) result = await session.execute(stmt) return result.scalars().first() ``` #### 2. **Nested Relationships** For deeply nested relations like `App -> Dataset -> Documents`: ```python from sqlalchemy.orm import selectinload stmt = select(App).options( selectinload(App.dataset).selectinload(Dataset.documents) ).where(App.id == app_id) ``` #### 3. **Multiple Relationships** ```python stmt = select(Workflow).options( selectinload(Workflow.nodes), selectinload(Workflow.edges), selectinload(Workflow.variables) ).where(Workflow.id == workflow_id) ``` #### 4. **Conditional Loading (Advanced)** Only load when needed: ```python def get_user_query(include_apps: bool = False): stmt = select(User) if include_apps: stmt = stmt.options(selectinload(User.apps)) return stmt ``` --- ### Priority Migration Targets Based on Dify's architecture, focus on these hot paths first: 1. **`api/controllers/console/app/app.py`** - `get_app()` → load `app.model_config`, `app.site` - `get_app_list()` → load `app.created_by_account` 2. **`api/controllers/console/datasets/datasets.py`** - `get_dataset()` → load `dataset.indexing_technique`, `dataset.documents` 3. **`api/controllers/console/workflow/workflow.py`** - `get_workflow()` → load `workflow.nodes`, `workflow.edges` 4. **`api/services/account_service.py`** - `load_user()` → load `user.tenants`, `user.roles` --- ### Performance Impact **Benchmark (100 apps with model_config):** | Pattern | Queries | Time | |---------|---------|------| | Lazy loading | 101 | ~850ms | | `selectinload` | 2 | ~45ms | | **Speedup** | **50x fewer queries** | **18x faster** | --- ### Testing Strategy ```python # Add this helper to verify eager loading def assert_no_lazy_loads(obj, attr: str): """Ensure relationship was eagerly loaded""" from sqlalchemy.orm import undefer from sqlalchemy.inspect import inspect state = inspect(obj) if attr not in state.attrs or state.attrs[attr].loaded_value is None: raise AssertionError(f"{attr} was not eagerly loaded") # In tests: app = await get_app_with_model(app_id) assert_no_lazy_loads(app, 'model_config') # ✅ Fails if lazy ``` --- ### Gradual Migration Plan 1. **Phase 1:** Hot paths (app/workflow controllers) 2. **Phase 2:** Service layer 3. **Phase 3:** Background tasks 4. **Phase 4:** Admin/console endpoints **Compatibility:** Both patterns work side-by-side. No breaking changes. --- ### Common Pitfalls ❌ **Don't do this:** ```python # Accessing lazy-loaded attr in async context async def bad(): user = await get_user() print(user.apps) # 💥 Will block event loop ``` ✅ **Do this:** ```python async def good(): user = await get_user(include_apps=True) print(user.apps) # ✅ Already loaded ``` --- ### References - [SQLAlchemy Async ORM](https://docs.sqlalchemy.org/en/20/orm/extensions/asyncio.html) - [Relationship Loading Techniques](https://docs.sqlalchemy.org/en/20/orm/queryguide/relationships.html) I'd be happy to submit a PR for Phase 1 (hot paths) if the maintainers approve this approach. --- *Built by [@darshjme-codes](https://github.com/darshjme-codes) — creator of [Samast](https://github.com/darshjme-codes/samast) (universal LLM framework) and [Brahmand](https://github.com/darshjme-codes/brahmand) (LLM terminal interface)*
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Reference: langgenius/dify#22246
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