[This topic is pre-release documentation and is subject to change in future releases. Blank topics are included as placeholders.]
Assembly: Db4objects.Db4o (in Db4objects.Db4o.dll)
for implementation of callback evaluations.
Namespace: Db4objects.Db4o.Query
Assembly: Db4objects.Db4o (in Db4objects.Db4o.dll)
Syntax
Visual Basic (Declaration) |
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Public Interface IEvaluation |
C# |
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public interface IEvaluation |
Visual C++ |
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public interface class IEvaluation |
Remarks
for implementation of callback evaluations.
To constrain a Db4objects.Db4o.Query.IQuery node with your own callback
, construct an object that implements the
interface and register it by passing it
to
Db4objects.Db4o.Query.IQuery.Constrain
.
Evaluations are called as the last step during query execution, after all other constraints have been applied. Evaluations in higher level Db4objects.Db4o.Query.IQuery nodes in the query graph are called first.
Java client/server only:
db4o first attempts to use Java Serialization to allow to pass final variables to the server. Please make sure that all variables that are used within the evaluate() method are Serializable. This may include the class an anonymous Evaluation object is created in. If db4o is not successful at using Serialization, the Evaluation is transported to the server in a db4o MemoryFile. In this case final variables can not be restored.
To constrain a Db4objects.Db4o.Query.IQuery node with your own callback
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Evaluation |
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Evaluation |
Evaluations are called as the last step during query execution, after all other constraints have been applied. Evaluations in higher level Db4objects.Db4o.Query.IQuery nodes in the query graph are called first.
Java client/server only:
db4o first attempts to use Java Serialization to allow to pass final variables to the server. Please make sure that all variables that are used within the evaluate() method are Serializable. This may include the class an anonymous Evaluation object is created in. If db4o is not successful at using Serialization, the Evaluation is transported to the server in a db4o MemoryFile. In this case final variables can not be restored.