| 摘要 |
A system that facilitates checking the consistency of a user-defined data type in relation to a database environment. The invention can employ a user-defined type (UDT) storage format whereby values can be self-describing, including the runtime type of the value. The invention can take the type definition that is persisted in the metadata catalogs as a streaming input and generate a type-specific state machine thereafter. At every point in the checking process, the type-specific state machine can be aware of the next data type that is to be encountered in the check. Whenever an embedded UDT is encountered, the current type-specific state machine can be suspended and saved. The embedded UDT can be checked before proceeding. In this way, the complex check can be effected using memory space proportional to the number of levels in the UDT as opposed to the number of bytes in the object.
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