摘要:
Techniques are provided for facilitating uniform access control to data managed by a database server that can emulate hierarchically organized systems, whether the data is accessed through hierarchical or relational access mechanisms. A database server that can emulate hierarchically organized systems uses separate relational or object-relational database tables to store the content of the resources that belong to a hierarchy (the “content structures”) and information that captures the hierarchy (the “hierarchy structures”). Both types of structures contain access control data that define consistent user access privileges. To determine access privileges for a user requesting access to data in the database, access control information is accessed in the hierarchy structures when the request is made through the hierarchical access mechanism, or accessed in the content structures when the request is made through a relational access mechanism. Access control is consistent between the hierarchical or relational access mechanisms because access through either is governed by user access data that reflects the same privileges.
摘要:
A method and system are provided for maintaining an XML index in response to piece-wise modifications on indexed XML documents. The database server that manages the XML index determines which nodes are involved in the piece-wise modifications, and updates the XML index based on only those nodes. Index entries for nodes not involved in the piece-wise modifications remain unchanged.
摘要:
A method, mechanism, and computer program product for storing, accessing, and managing XML data is disclosed. The approach supports efficient evaluation of XPath queries and also improves the performance of data/fragment extraction. The approach can be applied to schema-less documents. The approach is applicable to all database systems and other servers which support storing and managing XML content. In addition, the approach can be applied to store, manage, and retrieve other types of unstructured or semi-structured data in a database system.
摘要:
A method and system for the in-place evolution of XML schemas is disclosed. To automatically evolve an existing XML schema, a schema evolver receives both an existing XML schema and an XML document as input. The XML document indicates changes to be made to the existing XML schema. Based on the existing XML schema and the XML document, the schema evolver evolves the existing XML schema into a new XML schema that incorporates the changes indicated in the XML document. According to one aspect, the schema evolver generates one or more SQL statements based on the new XML schema. The SQL statements, when executed by a database server, cause the database server to evolve database structures that were based on the formerly existing XML schema so that the database structures conform to the new XML schema. This is accomplished “in place,” without copying the data in the database structures.
摘要:
Described is a method and system for storing data into a database, where a determination is made if schema metadata that is used to load the data into the database already exists, and where the existing schema metadata is used to load the data into the database if the schema metadata already exists. If the appropriate schema metadata does not exist, then it is generated and cached so that a later load operation for the same schema type will not need to re-generate this information. In this way, the cost to generate the schema metadata is amortized over multiple load operations to load data of the same schema type. The approach is protocol neutral so that multiple different protocol-based loads can operate with the same schema metadata information and load structures.
摘要:
Access control rewrites generate rewritten queries that may be executed more efficiently using index evaluation to determine which rows satisfy one or more access control conditions.
摘要:
An XML document can be represented in a compact binary form that maintains all of the features of XML data in a useable form. In response to a request for a modification (e.g., insert, delete or update a node) to an XML document that is stored in the compact binary form, a certain representation of the requested modification is computed for application directly to the binary form of the document. Thus, the requested modification is applied directly to the persistently stored binary form without constructing an object tree or materializing the XML document into a corresponding textual form. Taking into account the nature of the binary form in which the document is encoded, the bytes that actually require change are identified, including identifying where in the binary representation the corresponding actual changes need to be made.
摘要:
A validation procedure employs metadata reuse using composite path signatures to make a metadata reuse determination. The procedure is performed as part of validating a set of data objects. Validating an initial subset of data objects generates N different sets of object-specific metadata, each set of which is associated with a different composite path signature. When subsequently validating another data object, a composite path signature is generated for the data object and compared with the composite path signatures of the N different sets of object-specific metadata. If a match is found, then the object-specific metadata of the matching composite path signature is reused for the data object. The object-specific metadata is remapped to an in-memory representation of the data object.
摘要:
The techniques presented herein are directed towards providing a user-directed keyword-based search on a large collection of XML documents, and displaying a summary of results to the user. Prior to receiving search requests from a user, an offline analysis of a large collection of XML documents is performed to construct an inverted index of keywords. For each keyword, the index stores a set of location indicators that identify all the instances of the keyword found in the collection of documents. Once the index is constructed, keyword searching can be done efficiently by a keyword lookup in the index. Various display strategies enable the user to see the specific portion of a large XML document containing the keyword and/or path frequency information allowing the user to easily refine the search to specific paths within the collection of documents.
摘要:
Highly relevant search results for unstructured queries are efficiently identified from normalized data. A server graphs relationships between each of the data objects. For each search term, the server identifies a candidate set of data objects mapped to the term. The server calculates priority scores for the candidate data objects based at least in part on one or more of: a link analysis of the graph; or an analysis of metadata describing structural constraints upon the candidate data objects. Based on the graph, the server identifies one or more search result subgraphs, each comprising at least one data object from each of the candidate sets. The server looks for subgraphs in an order that is based on the priority scores for the candidate data objects. The server may terminate its search early, in part because prioritizing the candidate data objects increases the likelihood of receiving relevant search results first.