erpnext-database（erpnext 数据库）

ERPNext Database Operations

Quick Overview

Frappe provides three abstraction levels for database operations:

RULE: Always use the highest abstraction level appropriate for your use case.

Decision Tree

What do you want to do?
│
├─ Create/modify/delete document?
│  └─ frappe.get_doc() + .insert()/.save()/.delete()
│
├─ Get single document?
│  ├─ Changes frequently? → frappe.get_doc()
│  └─ Changes rarely? → frappe.get_cached_doc()
│
├─ List of documents?
│  ├─ With user permissions? → frappe.db.get_list()
│  └─ Without permissions? → frappe.get_all()
│
├─ Single field value?
│  ├─ Regular DocType → frappe.db.get_value()
│  └─ Single DocType → frappe.db.get_single_value()
│
├─ Direct update without triggers?
│  └─ frappe.db.set_value() or doc.db_set()
│
└─ Complex query with JOINs?
   └─ frappe.qb (Query Builder) or frappe.db.sql()

Most Used Patterns

Get Document

# With ORM (triggers validations)
doc = frappe.get_doc('Sales Invoice', 'SINV-00001')

# Cached (faster for frequently accessed docs)
doc = frappe.get_cached_doc('Company', 'My Company')

List Query

# With user permissions
tasks = frappe.db.get_list('Task',
    filters={'status': 'Open'},
    fields=['name', 'subject'],
    order_by='creation desc',
    page_length=50
)

# Without permissions
all_tasks = frappe.get_all('Task', filters={'status': 'Open'})

Single Value

# Single field
status = frappe.db.get_value('Task', 'TASK001', 'status')

# Multiple fields
subject, status = frappe.db.get_value('Task', 'TASK001', ['subject', 'status'])

# As dict
data = frappe.db.get_value('Task', 'TASK001', ['subject', 'status'], as_dict=True)

Create Document

doc = frappe.get_doc({
    'doctype': 'Task',
    'subject': 'New Task',
    'status': 'Open'
})
doc.insert()

Update Document

# Via ORM (with validations)
doc = frappe.get_doc('Task', 'TASK001')
doc.status = 'Completed'
doc.save()

# Direct (without validations) - use carefully!
frappe.db.set_value('Task', 'TASK001', 'status', 'Completed')

Filter Operators

{'status': 'Open'}                          # =
{'status': ['!=', 'Cancelled']}             # !=
{'amount': ['>', 1000]}                     # >
{'amount': ['>=', 1000]}                    # >=
{'status': ['in', ['Open', 'Working']]}     # IN
{'date': ['between', ['2024-01-01', '2024-12-31']]}  # BETWEEN
{'subject': ['like', '%urgent%']}           # LIKE
{'description': ['is', 'set']}              # IS NOT NULL
{'description': ['is', 'not set']}          # IS NULL

Query Builder (frappe.qb)

Task = frappe.qb.DocType('Task')

results = (
    frappe.qb.from_(Task)
    .select(Task.name, Task.subject)
    .where(Task.status == 'Open')
    .orderby(Task.creation, order='desc')
    .limit(10)
).run(as_dict=True)

With JOIN

SI = frappe.qb.DocType('Sales Invoice')
Customer = frappe.qb.DocType('Customer')

results = (
    frappe.qb.from_(SI)
    .inner_join(Customer)
    .on(SI.customer == Customer.name)
    .select(SI.name, Customer.customer_name)
    .where(SI.docstatus == 1)
).run(as_dict=True)

Caching

Basics

# Set/Get
frappe.cache.set_value('key', 'value')
value = frappe.cache.get_value('key')

# With expiry
frappe.cache.set_value('key', 'value', expires_in_sec=3600)

# Delete
frappe.cache.delete_value('key')

@redis_cache Decorator

from frappe.utils.caching import redis_cache

@redis_cache(ttl=300)  # 5 minutes
def get_dashboard_data(user):
    return expensive_calculation(user)

# Invalidate cache
get_dashboard_data.clear_cache()

Transactions

Framework manages transactions automatically:

Manual (rarely needed)

frappe.db.savepoint('my_savepoint')
try:
    # operations
    frappe.db.commit()
except:
    frappe.db.rollback(save_point='my_savepoint')

Critical Rules

1. NEVER Use String Formatting in SQL

# ❌ SQL Injection risk!
frappe.db.sql(f"SELECT * FROM `tabUser` WHERE name = '{user_input}'")

# ✅ Parameterized
frappe.db.sql("SELECT * FROM `tabUser` WHERE name = %(name)s", {'name': user_input})

2. NEVER Commit in Controller Hooks

# ❌ WRONG
def validate(self):
    frappe.db.commit()  # Never do this!

# ✅ Framework handles commits

3. ALWAYS Paginate

# ✅ Always limit
docs = frappe.get_all('Sales Invoice', page_length=100)

4. Avoid N+1 Queries

# ❌ N+1 problem
for name in names:
    doc = frappe.get_doc('Customer', name)

# ✅ Batch fetch
docs = frappe.get_all('Customer', filters={'name': ['in', names]})

Version Differences

v16 Aggregate Syntax

# v14/v15
fields=['count(name) as count']

# v16
fields=[{'COUNT': 'name', 'as': 'count'}]

Reference Files

See the references/ folder for detailed documentation:

• methods-reference.md - All Database and Document API methods
• query-patterns.md - Filter operators and Query Builder syntax
• caching-patterns.md - Redis cache patterns and @redis_cache
• examples.md - Complete working examples
• anti-patterns.md - Common mistakes and how to avoid them

Quick Reference