摘要:
A database system may utilize XML schema information to increase the efficiency of an XPath streaming evaluation. The database system may access XML schema or translation information during the evaluation of an element, attribute, or value in an XML data source. Based on the XML schema or translation information, the database system may determine matches to an XPath expression without decoding any binary-encoded data in the XML data source. Also, based on the XML schema information, the database may selectively skip or evaluate portions of the XML data source depending on whether those portions are defined in the XML schema so as to possibly contain a match to one or more unmatched steps in the XPath expression. XML schema information may be compiled into a compiled representation of the XPath expression for additional efficiencies.
摘要:
A modular repository is described, where operational features may be implemented without the need to scan every resource included in the modular repository. A modular repository includes a dedicated set of database objects containing all information needed to access the resources in the repository. For example, the database objects of a modular repository may include those user identifier mappings and ACL mappings, etc., to which metadata in the modular repository refers. A database system may also include a mechanism through which a modular repository may be mounted under a subdirectory of a common directory in the database system. The resources of a modular repository that are mounted under the common directory may be accessed through the common directory. Further, a client may query the resources of any modular repository mounted under the common directory by making the federated repository, represented by the common directory, the context of the query.
摘要:
Techniques are described herein for efficient and scalable processing of complex sets of XML schemas. The techniques described herein provide for reducing duplication of schema elements in volatile memory by building an XML schema in-memory model that stores repeating schema elements in in-memory data structures that are separate from in-memory data structures that store the parent schema elements which logically include or otherwise refer to the repeating schema elements. The techniques described herein also provide for faster generation of an in-memory model of an XML schema by pre-loading, in data structures on persistent storage, of schema elements from dependent XML schemas that are referenced and/or incorporated by the XML schema. The techniques described herein also provide for efficient processing of inter-dependent XML schemas by tracking all unresolved schema elements from dependent XML schemas and freeing the portions of volatile memory, which are used to process schema elements from the dependent XML schemas, as soon as the dependent schema elements being processed are stored in data structures on persistent storage.
摘要:
The approaches described herein provide an efficient way to process certain kinds of queries that retrieve XML data stored in an object-relational database. An XML query may include a predicate condition that joins two row sources. One or both of the row sources required for predicate evaluation may be path-based; that is, consume and produce rows of XMLType data. Such a path-based row source may be modified to use the predicate condition to filter the rows it generates so that only rows satisfying the predicate condition need to be further processed. A small cache structure introduced into the path-based row source may be used to optimize the evaluation of the predicate row. Once populated with row data, the cache structure may be reorganized to optimize the performance of predicate evaluation.
摘要:
Techniques are provided for incrementally maintaining an XML index built to access XML data that is encoded in binary XML form. Rather than delete and reinsert index entries of all the nodes of a modified XML document, only the index entries of the affected nodes are modified. Consequently, the order key values stored in the index may become inconsistent with the current hierarchical locations of the nodes to which the order key values correspond. Techniques are described for resolving the inconsistencies, and for addressing additional problems that result when the XML index is path-subsetted.
摘要:
A database system may utilize XML schema information to increase the efficiency of an XPath streaming evaluation. The database system may access XML schema or translation information during the evaluation of an element, attribute, or value in an XML data source. Based on the XML schema or translation information, the database system may determine matches to an XPath expression without decoding any binary-encoded data in the XML data source. Also, based on the XML schema information, the database may selectively skip or evaluate portions of the XML data source depending on whether those portions are defined in the XML schema so as to possibly contain a match to one or more unmatched steps in the XPath expression. XML schema information may be compiled into a compiled representation of the XPath expression for additional efficiencies.
摘要:
Techniques are provided for ensuring lexical fidelity when an XML document is stored in a binary format. Operations, on the XML data, that would cause the loss of lexical fidelity between the original XML document and the binary-encoded version of the XML document are not performed. Such operations include the removal of unnecessary whitespace characters, certain data type conversions, CRLF normalization, the “collapsing” of two-tag empty elements into a single tag empty element, and the replacing of entity references or numeric character references with another value. An XML schema, to which the XML document conforms, may indicate that the XML document is to be stored in a lexical fidelity mode. Additionally, or alternatively, the database statement that (when executed) causes the XML document to be stored in a binary format may so indicate.
摘要:
Techniques for implementing fast loading of binary XML into a binary XML database repository are provided. A client application reduces the processing burden on the repository by doing pre-processing of the binary XML data prior to loading.
摘要:
A method and apparatus for validating XML documents in a streaming fashion is provided. A streaming validator validates an XML document by comparing the contents of the XML document to an XML schema. Tokens are generated for each element or attribute of the XML schema and for each element or attribute of the XML document using the same generator token function. The elements and attributes of the XML document and XML schema are compared using tokens rather than string comparisons to perform the validation more efficiently.
摘要:
A method and system for evolving XML-schema-based data to conform to an evolved XML schema is disclosed. Based on an existing XML schema and an instance document that is based on the existing XML schema, an XML-schema-independent form of the instance document is generated. Based on a set of specified transformations and the XML-schema-independent form of the instance document, an evolved instance document is generated. The evolved instance document conforms to an evolved XML schema that incorporates changes to the existing XML schema. Techniques described herein are flexible enough to accommodate a wide variety of evolutions to XML schemas.