1.5.0

Released: January 18, 2021

changed

• [changed] [environment] To accommodate SQLAlchemy 1.4 and 2.0, the migration model now no longer
  assumes that the SQLAlchemy Connection will autocommit an individual
  operation. This essentially means that for databases that use
  non-transactional DDL (pysqlite current driver behavior, MySQL), there is
  still a BEGIN/COMMIT block that will surround each individual migration.
  Databases that support transactional DDL should continue to have the
  same flow, either per migration or per-entire run, depending on the
  value of the Environment.configure.transaction_per_migration
  flag.

• [changed] [environment] A CommandError is raised if a sqlalchemy.engine.Engine is
  passed to the MigrationContext.configure() method instead of a
  sqlalchemy.engine.Connection object. Previously, this would be a
  warning only.

• [changed] Alembic 1.5.0 now supports Python 2.7 and Python 3.6 and above, as well
  as SQLAlchemy 1.3.0 and above. Support is removed for Python 3
  versions prior to 3.6 and SQLAlchemy versions prior to the 1.3 series.

  References: #748

feature

• [feature] [autogenerate] Added new hook EnvironmentContext.configure.include_name,
  which complements the
  EnvironmentContext.configure.include_object hook by providing
  a means of preventing objects of a certain name from being autogenerated
  before the SQLAlchemy reflection process takes place, and notably
  includes explicit support for passing each schema name when
  EnvironmentContext.configure.include_schemas is set to True.
  This is most important especially for enviroments that make use of
  EnvironmentContext.configure.include_schemas where schemas are
  actually databases (e.g. MySQL) in order to prevent reflection sweeps of
  the entire server.

  References: #650

• [feature] [versioning] The revision tree is now checked for cycles and loops between revision
  files when the revision environment is loaded up. Scenarios such as a
  revision pointing to itself, or a revision that can reach itself via a
  loop, are handled and will raise the CycleDetected exception when
  the environment is loaded (expressed from the Alembic commandline as a
  failure message and nonzero return code). Previously, these situations were
  silently ignored up front, and the behavior of revision traversal would
  either be silently incorrect, or would produce errors such as
  RangeNotAncestorError. Pull request courtesy Koichiro Den.

  References: #757

bug

• [bug] [operations] Modified the add_column() operation such that the Column object in
  use is shallow copied to a new instance if that Column is already
  attached to a table() or Table. This accommodates for the change
  made in SQLAlchemy issue #5618 which prohibits a Column from being
  associated with multiple table() objects. This resumes support for
  using a Column inside of an Alembic operation that already refers to a
  parent table() or Table as well as allows operation objects just
  autogenerated to work.

  References: #753

• [bug] [autogenerate] Added rendering for the Table.prefixes element to autogenerate so that
  the rendered Python code includes these directives. Pull request courtesy
  Rodrigo Ce Moretto.

  References: #721

• [bug] [batch] Added missing "create comment" feature for columns that are altered in
  batch migrations.

  References: #761

• [bug] [batch] Made an adjustment to the PostgreSQL dialect to allow it to work more
  effectively in batch mode, where a datatype like Boolean or non-native Enum
  that may have embedded rules to generate CHECK constraints will be more
  correctly handled in that these constraints usually will not have been
  generated on the PostgreSQL backend; previously it would inadvertently
  assume they existed unconditionally in a special PG-only "drop constraint"
  step.

  References: #773

usecase

• [usecase] [operations] Added support for rendering of "identity" elements on
  Column objects, supported in SQLAlchemy via
  the Identity element introduced in version 1.4.

  Adding columns with identity is supported on PostgreSQL,
  MSSQL and Oracle. Changing the identity options or removing
  it is supported only on PostgreSQL and Oracle.

  References: #730

• [usecase] [commands] Add __main__.py file to alembic package to support invocation
  with python -m alembic.

removed

• [removed] [autogenerate] The long deprecated
  EnvironmentContext.configure.include_symbol hook is removed.
  The EnvironmentContext.configure.include_object
  and EnvironmentContext.configure.include_name
  hooks both achieve the goals of this hook.

• [removed] [commands] Removed deprecated --head_only option to the alembic current
  command

• [removed] [operations] Removed legacy parameter names from operations, these have been emitting
  warnings since version 0.8. In the case that legacy version files have not
  yet been updated, these can be modified directly in order to maintain
  compatibility:

  -   `Operations.drop_constraint()` - "type" (use "type_") and "name"
      (use "constraint_name")
  
  -   `Operations.create_primary_key()` - "cols" (use "columns") and
      "name" (use "constraint_name")
  
  -   `Operations.create_unique_constraint()` - "name" (use
      "constraint_name"), "source" (use "table_name") and "local_cols" (use
      "columns")
  
  -   `Operations.batch_create_unique_constraint()` - "name" (use
      "constraint_name")
  
  -   `Operations.create_foreign_key()` - "name" (use "constraint_name"),
      "source" (use "source_table"), "referent" (use "referent_table")
  
  -   `Operations.batch_create_foreign_key()` - "name" (use
      "constraint_name"), "referent" (use "referent_table")
  
  -   `Operations.create_check_constraint()` - "name" (use
      "constraint_name"), "source" (use "table_name")
  
  -   `Operations.batch_create_check_constraint()` - "name" (use
      "constraint_name")
  
  -   `Operations.create_index()` - "name" (use "index_name")
  
  -   `Operations.drop_index()` - "name" (use "index_name"), "tablename"
      (use "table_name")
  
  -   `Operations.batch_drop_index()` - "name" (use "index_name"),
  
  -   `Operations.create_table()` - "name" (use "table_name")
  
  -   `Operations.drop_table()` - "name" (use "table_name")
  
  -   `Operations.alter_column()` - "name" (use "new_column_name")