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DDL Generation

DDL generation is implemented by AltibaseDDLCompiler and coordinated with dialect table events.

CREATE TABLE generation

get_column_specification() composes each column definition.

  • Non-autoincrement columns:
  • use AltibaseTypeCompiler output
  • include DEFAULT ... when server default exists
  • include NOT NULL when column is not nullable
  • Autoincrement integer primary key columns (without explicit server default):
  • force type INTEGER
  • generate DEFAULT <table>_<column>_SEQ.NEXTVAL

Example generated shape:

CREATE TABLE users (
    id INTEGER DEFAULT users_id_SEQ.NEXTVAL NOT NULL,
    name VARCHAR(100) NOT NULL
)

Comments

The compiler supports table and column comments:

  • visit_set_table_comment
  • visit_drop_table_comment
  • visit_set_column_comment
  • post_create_table (inline extra statement after CREATE TABLE)

Rendered forms:

COMMENT ON TABLE users IS 'table comment'
COMMENT ON COLUMN users.id IS 'identifier'
COMMENT ON TABLE users IS ''

Implicit sequence lifecycle

Autoincrement sequence management is done by table event listeners in dialect.py:

  • before_create: create implicit sequence
  • after_drop: drop implicit sequence (errors ignored)

mermaid flowchart TD A[MetaData.create_all] --> B[before_create listener] B --> C[CREATE SEQUENCE table_col_SEQ] C --> D[AltibaseDDLCompiler CREATE TABLE] D --> E[column DEFAULT table_col_SEQ.NEXTVAL] F[MetaData.drop_all] --> G[after_drop listener] G --> H[DROP SEQUENCE table_col_SEQ]

Event-driven sequence creation

If DDL is generated and executed outside SQLAlchemy table events, you must create/drop sequences yourself.

Example

from sqlalchemy import Column, Integer, MetaData, String, Table, create_engine

engine = create_engine("altibase://sys:password@localhost:20300/mydb")
m = MetaData()

users = Table(
    "users",
    m,
    Column("id", Integer, primary_key=True, autoincrement=True),
    Column("name", String(100), nullable=False, comment="user name"),
    comment="application users",
)

m.create_all(engine)

Alembic Migration Support

This dialect ships with an Alembic DDLImpl registered via alembic.ddl entry point. After installing sqlalchemy-pyaltibase, Alembic migrations work automatically.

Key behavior: transactional_ddl = False — Altibase auto-commits DDL statements, so Alembic will not wrap migrations in a transaction.

# alembic.ini
sqlalchemy.url = altibase://sys:password@localhost:20300/mydb

alembic upgrade head

Install Alembic extra

pip install "sqlalchemy-pyaltibase[alembic]" to pull in Alembic as a dependency.