Schema Management

Complete reference for schema operations, conflict detection, and migrations in TypeBridge.

Overview

TypeBridge provides comprehensive schema management with automatic conflict detection to prevent accidental data loss during schema changes. The schema system ensures safe evolution of your database schema over time.

SchemaManager

The SchemaManager class handles schema registration, generation, and synchronization:

from type_bridge import SchemaManager, Database

# Connect to database
db = Database(address="localhost:1729", database="mydb")
db.connect()

# Create schema manager
schema_manager = SchemaManager(db)

SchemaManager Methods

class SchemaManager:
    def register(self, *models: type[Entity] | type[Relation]) -> None:
        """Register entity or relation types."""

    def generate_schema(self) -> str:
        """Generate TypeQL schema from registered models."""

    def sync_schema(self, force: bool = False) -> None:
        """Sync schema to database. Use force=True to recreate (⚠️ DATA LOSS)."""

    def collect_schema_info(self) -> SchemaInfo:
        """Collect current schema information."""

    def compare_schemas(self, old: SchemaInfo, new: SchemaInfo) -> SchemaDiff:
        """Compare two schemas and return differences."""

Basic Schema Operations

Register Models

Register entity and relation types before generating schema:

from type_bridge import Entity, Relation, TypeFlags, Role

class Person(Entity):
    flags = TypeFlags(name="person")
    name: Name = Flag(Key)
    age: Age | None = None

class Company(Entity):
    flags = TypeFlags(name="company")
    name: Name = Flag(Key)

class Employment(Relation):
    flags = TypeFlags(name="employment")
    employee: Role[Person] = Role("employee", Person)
    employer: Role[Company] = Role("employer", Company)
    position: Position

# Register all models
schema_manager.register(Person, Company, Employment)

Generate TypeQL Schema

Generate TypeQL schema from registered models:

# Generate schema string
typeql_schema = schema_manager.generate_schema()

print(typeql_schema)
# Output:
# define
#
# attribute name, value string;
# attribute age, value integer;
# attribute position, value string;
#
# entity person,
#     owns name @key,
#     owns age @card(0..1);
#
# entity company,
#     owns name @key;
#
# relation employment,
#     relates employee,
#     relates employer,
#     owns position @card(1..1);
#
# person plays employment:employee;
# company plays employment:employer;

Sync Schema to Database

Synchronize generated schema to TypeDB:

# First time - creates schema
schema_manager.sync_schema()  # ✅ Success

# Subsequent calls - validates compatibility
schema_manager.sync_schema()  # ✅ Success if compatible

Conflict Detection

SchemaManager automatically detects breaking changes and prevents data loss:

Detecting Conflicts

from type_bridge.schema import SchemaConflictError

# Initial schema creation
schema_manager.register(Person, Company, Employment)
schema_manager.sync_schema()  # ✅ Creates schema

# Modify your models (remove an attribute - BREAKING CHANGE)
class Person(Entity):
    flags = TypeFlags(name="person")
    name: Name = Flag(Key)
    # age attribute removed!

# Re-register and attempt to sync
schema_manager = SchemaManager(db)
schema_manager.register(Person, Company, Employment)

try:
    schema_manager.sync_schema()  # ❌ Raises SchemaConflictError
except SchemaConflictError as e:
    print("Schema conflict detected!")
    print(e.diff.summary())
    # Output:
    # Schema Differences:
    # Modified Entities:
    #   person:
    #     - Removed attributes: age

Force Recreate (DATA LOSS)

Use force=True to drop and recreate the database:

# ⚠️ WARNING: This drops the entire database and recreates it
# ALL DATA WILL BE LOST
schema_manager.sync_schema(force=True)

Use force mode only when: - You're in development and don't need existing data - You've backed up your data - You're intentionally resetting the database

Schema Comparison

Compare schemas to understand changes before applying them:

Collect Schema Information

from type_bridge.schema import SchemaInfo

# Collect current schema
old_schema = schema_manager.collect_schema_info()

# Modify your models
class Person(Entity):
    flags = TypeFlags(name="person")
    name: Name = Flag(Key)
    age: Age | None = None
    email: Email = Flag(Unique)  # ✅ New attribute added!

# Collect new schema
schema_manager = SchemaManager(db)
schema_manager.register(Person)
new_schema = schema_manager.collect_schema_info()

# Compare
diff = old_schema.compare(new_schema)

View Schema Differences

# Check if there are changes
if diff.has_changes():
    print(diff.summary())
    # Output:
    # Schema Differences:
    # Modified Entities:
    #   person:
    #     + Added attributes: email (unique)

# Check for breaking changes
if diff.has_breaking_changes():
    print("WARNING: Breaking changes detected!")
else:
    print("Safe to apply changes")

Schema Diff Details

The SchemaDiff class provides granular change tracking:

Top-Level Changes

# Added/removed types
print(f"Added entities: {diff.added_entities}")
print(f"Removed entities: {diff.removed_entities}")
print(f"Added relations: {diff.added_relations}")
print(f"Removed relations: {diff.removed_relations}")
print(f"Added attributes: {diff.added_attributes}")
print(f"Removed attributes: {diff.removed_attributes}")

Entity Changes

# Check entity modifications
for entity_type, changes in diff.modified_entities.items():
    print(f"\n{entity_type} changes:")
    print(f"  Added attributes: {changes.added_attributes}")
    print(f"  Removed attributes: {changes.removed_attributes}")

    # Check attribute flag changes (cardinality, key, unique)
    for attr_name, flag_change in changes.modified_attributes.items():
        print(f"  Modified {attr_name}:")
        print(f"    Old flags: {flag_change.old_flags}")
        print(f"    New flags: {flag_change.new_flags}")

Relation Changes

# Check relation modifications
for relation_type, changes in diff.modified_relations.items():
    print(f"\n{relation_type} changes:")
    print(f"  Added roles: {changes.added_roles}")
    print(f"  Removed roles: {changes.removed_roles}")
    print(f"  Added attributes: {changes.added_attributes}")
    print(f"  Removed attributes: {changes.removed_attributes}")

    # Check role changes
    for role_name, role_change in changes.modified_roles.items():
        print(f"  Modified role {role_name}:")
        print(f"    Old type: {role_change.old_type}")
        print(f"    New type: {role_change.new_type}")

SchemaDiff Structure

@dataclass
class SchemaDiff:
    # Top-level changes
    added_entities: set[str]
    removed_entities: set[str]
    added_relations: set[str]
    removed_relations: set[str]
    added_attributes: set[str]
    removed_attributes: set[str]

    # Detailed changes
    modified_entities: dict[str, EntityChanges]
    modified_relations: dict[str, RelationChanges]

    def has_changes(self) -> bool:
        """Check if there are any changes."""

    def has_breaking_changes(self) -> bool:
        """Check if there are breaking changes (removals, type changes)."""

    def summary(self) -> str:
        """Get human-readable summary of changes."""

@dataclass
class EntityChanges:
    added_attributes: set[str]
    removed_attributes: set[str]
    modified_attributes: dict[str, FlagChange]

@dataclass
class RelationChanges:
    added_roles: set[str]
    removed_roles: set[str]
    added_attributes: set[str]
    removed_attributes: set[str]
    modified_roles: dict[str, RoleChange]
    modified_attributes: dict[str, FlagChange]

Schema Validation Rules

TypeBridge enforces validation rules during schema generation to prevent TypeDB errors:

Duplicate Attribute Type Detection

Each semantic field must use a distinct attribute type:

from type_bridge.schema import SchemaValidationError

# ❌ WRONG: Duplicate attribute types
class TimeStamp(DateTime):
    pass

class Issue(Entity):
    key: IssueKey = Flag(Key)
    created: TimeStamp   # Error: duplicate attribute type
    modified: TimeStamp  # TypeDB sees only one ownership

# Raises SchemaValidationError during generate_schema():
# "TimeStamp used in fields: 'created', 'modified'"

# ✅ CORRECT: Distinct attribute types
class CreatedStamp(DateTime):
    pass

class ModifiedStamp(DateTime):
    pass

class Issue(Entity):
    key: IssueKey = Flag(Key)
    created: CreatedStamp   # ✅ Distinct type
    modified: ModifiedStamp # ✅ Distinct type

Why this matters: TypeDB stores attribute types, not field names. Using the same type for multiple fields causes cardinality conflicts because TypeDB sees a single ownership relationship.

Reserved Word Validation

TypeBridge validates that type names don't use TypeDB/TypeQL reserved words:

# ❌ WRONG: Using reserved words
class Type(Entity):  # Error: 'type' is reserved
    pass

class Match(Entity):  # Error: 'match' is reserved
    pass

# ✅ CORRECT: Use different names
class ContentType(Entity):
    pass

class MatchResult(Entity):
    pass

Migration Manager

For complex schema migrations, use MigrationManager:

from type_bridge.schema import MigrationManager

migration_manager = MigrationManager(db)

Add Migrations

# Add individual migration
migration_manager.add_migration(
    name="add_email_to_person",
    schema="define person owns email;"
)

# Add complex migration
migration_manager.add_migration(
    name="add_company_entity",
    schema="""
    define
    entity company,
        owns name @key,
        owns industry;

    attribute industry, value string;
    """
)

# Add migration with data transformation
migration_manager.add_migration(
    name="split_name_field",
    schema="""
    define
    person owns first-name,
        owns last-name;

    attribute first-name, value string;
    attribute last-name, value string;
    """,
    data_script="""
    # TypeQL to transform data
    match
    $p isa person, has name $n;
    # ... split logic
    """
)

Apply Migrations

# Apply all pending migrations in order
migration_manager.apply_migrations()

# Apply specific migration
migration_manager.apply_migration("add_email_to_person")

# Check migration status
status = migration_manager.get_migration_status()
print(f"Applied: {status.applied}")
print(f"Pending: {status.pending}")

Complete Schema Workflow

from type_bridge import (
    Database, SchemaManager,
    Entity, Relation, TypeFlags, Role,
    String, Integer, Date,
    Flag, Key, Unique, Card
)
from type_bridge.schema import SchemaConflictError

# 1. Define models
class UserID(String):
    pass

class Username(String):
    pass

class Email(String):
    pass

class User(Entity):
    flags = TypeFlags(name="user")
    user_id: UserID = Flag(Key)
    username: Username
    email: Email = Flag(Unique)

# 2. Connect to database
db = Database(address="localhost:1729", database="mydb")
db.connect()

# 3. Create schema manager
schema_manager = SchemaManager(db)

# 4. Register models
schema_manager.register(User)

# 5. Generate and view schema
typeql = schema_manager.generate_schema()
print("Generated schema:")
print(typeql)

# 6. Sync to database
try:
    schema_manager.sync_schema()
    print("✅ Schema synchronized successfully")
except SchemaConflictError as e:
    print("❌ Schema conflict detected:")
    print(e.diff.summary())
    print("\nUse force=True to recreate (⚠️ DATA LOSS)")

# 7. Later: Modify models
class User(Entity):
    flags = TypeFlags(name="user")
    user_id: UserID = Flag(Key)
    username: Username
    email: Email = Flag(Unique)
    created_at: CreatedAt  # ✅ New attribute - safe change

# 8. Compare schemas
old_schema = schema_manager.collect_schema_info()
schema_manager = SchemaManager(db)
schema_manager.register(User)
new_schema = schema_manager.collect_schema_info()

diff = old_schema.compare(new_schema)
if diff.has_changes():
    print("Schema changes detected:")
    print(diff.summary())

    if diff.has_breaking_changes():
        print("⚠️ Breaking changes - review carefully")
    else:
        print("✅ Safe to apply")

# 9. Apply changes
schema_manager.sync_schema()  # Applies safe changes

Best Practices

1. Always Check for Conflicts

# ✅ GOOD: Handle conflicts
try:
    schema_manager.sync_schema()
except SchemaConflictError as e:
    print(e.diff.summary())
    # Decide whether to force or modify schema

# ❌ POOR: Ignore conflicts
schema_manager.sync_schema(force=True)  # ⚠️ DATA LOSS

2. Use Distinct Attribute Types

# ✅ GOOD: Each field has distinct type
class CreatedAt(DateTime):
    pass

class UpdatedAt(DateTime):
    pass

class Record(Entity):
    created_at: CreatedAt
    updated_at: UpdatedAt

# ❌ WRONG: Duplicate attribute types
class Timestamp(DateTime):
    pass

class Record(Entity):
    created_at: Timestamp  # Error!
    updated_at: Timestamp

3. Review Changes Before Applying

# ✅ GOOD: Review changes
diff = old_schema.compare(new_schema)
print(diff.summary())

if diff.has_breaking_changes():
    confirm = input("Breaking changes detected. Continue? (yes/no): ")
    if confirm.lower() == "yes":
        schema_manager.sync_schema(force=True)
else:
    schema_manager.sync_schema()

# ❌ POOR: Blindly apply
schema_manager.sync_schema(force=True)

4. Use Migrations for Complex Changes

# ✅ GOOD: Use migrations for multi-step changes
migration_manager.add_migration(
    name="refactor_user_fields",
    schema="""...""",
    data_script="""..."""
)
migration_manager.apply_migrations()

# ❌ POOR: Force recreate loses data
schema_manager.sync_schema(force=True)

5. Version Control Your Schemas

# ✅ GOOD: Keep schema history
# models/v1/user.py
class User(Entity):
    user_id: UserID = Flag(Key)

# models/v2/user.py
class User(Entity):
    user_id: UserID = Flag(Key)
    email: Email = Flag(Unique)  # Added in v2

See Also

• Entities - Entity definition
• Relations - Relation definition
• Attributes - Attribute types
• Validation - Schema validation rules