摘要:
Various techniques are described hereafter for improving the efficiency of binary XML encoding and loading operations. In particular, techniques are described for incrementally encoding XML in response to amount-based requests. After encoding enough binary XML to satisfy an amount-based request, the encoder stops encoding the XML until a subsequent request is received. The incremental encoding may take place on the client-side or the server-side. Techniques are also described for reducing the character set conversion operations by having a parser convert tokens in text XML into one character set while converting non-token text in the text XML into another character set. Techniques are also described for generating self-contained binary XML documents, and for improving remap operations by providing a binary XML document on a chunk-by-chunk basis.
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.
摘要:
Techniques are provided for indexing XML documents using path subsetting. According to one embodiment, a PATH table created for storing one row for each indexed node of the XML documents using user-defined criteria. The user-defined criteria are used to determine which nodes of XML documents to included in The PATH TABLE. 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. Use of the user defined criteria is transparent to any query improves DML indexes overhead costs.
摘要:
A method and system of handling document operation requests on documents with large collections and constrained memory is disclosed. In some embodiments, when one or more collection elements of a document are required to be in memory for a document operation, each of the one or more required collection elements not already in the memory are loaded into a collection partition in the memory before the document operation is executed.
摘要:
A method and apparatus is provided for translating queries, such as path expressions and SQL/XML constructs, into SQL statements to be executed against an XML index, which improves processor time as opposed to applying path expressions directly to the original XML documents to extract the desired information. Simple path expressions, filter expressions, descendant axes, wildcards, logical expressions, relational expressions, literals, and other path expressions are all translated into SQL for efficient querying of an XML index. Similarly, rules for translating SQL/XML constructs into SQL are provided.
摘要:
Techniques are provided for indexing XML documents using abridged indexes. According to one embodiment, a value index is created for each node of an XML documents as specified by one or more criteria. The criteria are used to determine one or more paths of XML documents. For each path specified, a abridged index is created and maintained. When processing a query in a DBMS that utilizes abridged indexes the abridged indexes are used instead the XML index, provided the abridged index can satisfy the query. Use of the abridged indexes improves the efficiency of XPath queries performance.
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 system are provided for allowing users to register XML schemas in a database system. The database system determines, based on a registered XML schema, how to store within the database system XML documents that conform to the XML schema. This determination involves mapping constructs defined in the XML schema to constructs supported by the database system. Such constructs may include datatypes, hierarchical relationship between elements, constraints, inheritances, etc. Once the mapping has been determined, it is stored and used by the database system to determine how to store subsequently received XML documents that conform to the registered XML schema.
摘要:
Techniques for managing hierarchical data include managing a link table in a relational database. The hierarchical data includes data about a hierarchy of nodes related by multiple links. The link table includes first information, second information and link information, for each link. First information indicates a first node in the hierarchical data. Second information indicates a second node that is associated with the first node by the link. Link information indicates values for link attributes of the link between the first node and the second node, and does not indicate a value for any attribute of the first node alone or any attribute of the second node alone. The techniques support directing a single SQL statement to a path database object, constructed based on the link table, in order to obtain paths that satisfy a search on link attributes.
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.