摘要:
Techniques and systems are provided for efficiently managing hierarchical relational data stored in object-relational database system by extending the syntax of the database language supported by the database system (e.g. SQL) to incorporate several new “hierarchical” operators. These operators are evaluated based on the hierarchical relationship defined for hierarchical relational data. The operators maybe incorporated in SQL queries along with relational operators.
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 database server determines, on an element-level of granularity, what form of VARRAY storage to map collections of elements defined by a XML schema. A collection element may be mapped to an in-line VARRAY or an out-of-line VARRAY. The determination may based on a variety of factors, including the database type mapped to the collection element, database limitations that limit the form storage for certain database types, and annotations (“mapping annotations”) embedded within that XML schema that specifying a database type for database representation of a collection element or a form of VARRAY storage.
摘要:
A method and apparatus for efficiently maintaining XML index structures in a database system is provided. Instead of immediately synchronizing the XML index structures for every change submitted to the database, the changes are stored in a PENDING table. The XML index structures are periodically synchronized, based on certain criteria or at a user's discretion. Between synchronizations, the XML index structures may be in stale mode or current mode. If in stale mode, a request to access indexed information will use the XML index structures to find the desired indexed information without checking the PENDING table. If in current mode, a request to access indexed information will search the XML index structures and also check the PENDING table to determine 1) whether the indexed information has been updated or deleted, and 2) whether information relevant to the request has been inserted or updated.
摘要:
A method and system are provided for extracting a valid, self-contained fragment for a node in a XML document stored in a database management system. An XML index is used to identify a location in which XML fragment data corresponding to the node is located. Ancestors of the node are identified and examined for any information needed for the proper interpretation of the fragment. If an ancestor node contains such needed information, this information is patched into the XML fragment to ensure that the fragment is a valid, self-contained XML fragment.
摘要:
Techniques are provided for indexing XML documents. According to one embodiment, a PATH table created for storing one row for each indexed node of the XML documents. The PATH table row for a node includes (1) information for locating the XML document that contains the node, (2) information that identifies the path of the node, and (3) information that identifies the position of the node within the hierarchical structure of the XML document that contains the node. If the node is associated with the value, then the PATH table row for the node may also include the value. Use of the PATH table to answer XPath queries is facilitated by secondary indexes.
摘要:
A method and system are provided for determining whether a given path is an indexed path of XML documents stored in a database management system. A finite state machine is built using the path subsetting rules specified by a user. The finite state machine is traversed using the given path. If any accepting states are reached during the traversal of the finite state machine, the given path is determined to matching the path subsetting rules.
摘要:
To improve performance of performing XML operations on an XML document in by a client tier, the client generates an index that indexes the nodes of an XML document. The index may be generated, for example, by and during parsing of the XML document. The index contains similar structures to those maintained by a database server to perform XML operations on collections of XML documents. In lieu of parsing XML document to generate an index, the client may generate indexes based on data retrieved from the indexes at the database server.
摘要:
A method and apparatus for efficiently maintaining XML index structures in a database system is provided. Instead of immediately synchronizing the XML index structures for every change submitted to the database, the changes are stored in a PENDING table. The XML index structures are periodically synchronized, based on certain criteria or at a user's discretion. Between synchronizations, the XML index structures may be in stale mode or current mode. If in stale mode, a request to access indexed information will use the XML index structures to find the desired indexed information without checking the PENDING table. If in current mode, a request to access indexed information will search the XML index structures and also check the PENDING table to determine 1) whether the indexed information has been updated or deleted, and 2) whether information relevant to the request has been inserted or updated.
摘要:
Cost-based optimizer functionality for an XML database repository provides means for optimizing the execution of database queries that access XML resources in the database repository. Statistics about XML resources that are stored in the database repository are gathered, stored and utilized by a query optimizer to compute computational costs associated with each of multiple methods of accessing particular XML resources requested in a database query. Hence, the optimizer is able to select the most efficient query execution plan based on the costs of possible access paths. In one embodiment, specific statistics about the hierarchical structure of XML resources stored in the XML database repository are gathered, stored in a relational table in the database management system, and used to compute the selectivity of query predicates and the index cost associated with traversing one or more indexes to access requested XML resources.