# Package org.apache.cayenne.merge

- Interface Summary
  Interface | Description
  --- | ---
  MergerContext | An object passed as an argument to `MergerToken.execute(MergerContext)`s that a `MergerToken` can do its work.
  MergerToken |
  ModelMergeDelegate | A interface used to tell about modifications performed on the model by `MergerToken` with `MergeDirection.TO_MODEL`
  ValueForNullProvider |

- Class Summary
  Class | Description
  --- | ---
  AbstractToDbToken | Common abstract superclass for all `MergerToken`s going from the model to the database.
  AbstractToModelToken | Common abstract superclass for all `MergerToken`s going from the database to the model.
  AddColumnToDb |
  AddColumnToModel | A `MergerToken` to add a `DbAttribute` to a `DbEntity`.
  AddRelationshipToDb |
  AddRelationshipToModel |
  CreateTableToDb |
  CreateTableToModel | A `MergerToken` to add a `DbEntity` to a `DataMap`
  DbMerger | Traverse a `DataNode` and a `DataMap` and create a group of `MergerToken`s to alter the `DataNode` data store to match the `DataMap`.
  DefaultValueForNullProvider |
  DropColumnToDb |
  DropColumnToModel | A `MergerToken` to remove a `DbAttribute` from a `DbEntity`.
  DropRelationshipToDb |
  DropRelationshipToModel |
  DropTableToDb |
  DropTableToModel | A `MergerToken` to remove a `DbEntity` from a `DataMap`.
  ExecutingMergerContext |
  MergerFactory | All `MergerToken`s should be created from a `MergerFactory` obtained from `DbAdapter.mergerFactory()` so that the `DbAdapter` are able to provide `MergerToken` subclasses.
  SetAllowNullToDb | A `MergerToken` to add a "allow null" clause to a column.
  SetAllowNullToModel | A `MergerToken` to set the mandatory field of a `DbAttribute` to false
  SetColumnTypeToDb | An `MergerToken` to use to set type, length and precision.
  SetColumnTypeToModel | A `MergerToken` that modifies one original `DbAttribute` to match another new `DbAttribute`s type, maxLength and precision.
  SetNotNullToDb | A `MergerToken` to add a "not null" clause to a column.
  SetNotNullToModel | A `MergerToken` to set the mandatory field of a `DbAttribute` to true
  SetPrimaryKeyToDb |
  SetPrimaryKeyToModel |
  SetValueForNullToDb |

- Enum Summary
  Enum | Description
  --- | ---
  MergeDirection | Represent a merge direction that can be one of two.

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