摘要:
A method and apparatus for optimizing XML queries over heterogeneous XML tables is provided. A query that targets a container (e.g. table or collection) that contains a plurality of XML documents is received, wherein at least two XML documents in the plurality do not conform to the same schema. Based on the received query, a plurality of execution plans is generated. Each execution plan is associated with a different XML schema. An execution plan is used to execute the query relative to those XML documents that conform to the XML schema associated with the execution plan.
摘要:
Techniques for determining whether an XML query may be written are provided. In one scenario, an XML query includes an expandable path, which is a path expression that includes a wildcard character (*) or a descendant axis (//). An XML schema is used to generate multiple expanded paths (each of which is a simple path expression) from the expandable path. The XML schema is used to compare each expanded path to another expanded path and to determine whether the nodes identified by the respective expanded paths are guaranteed to occur in a particular order in XML documents that conform to the XML schema. In another scenario, an XML query includes an order operator that takes two paths as input. Similarly, an XML schema is used to compare the two paths and to determine whether the nodes identified by the two paths are guaranteed to occur in a particular order in XML documents that conform to the XML schema.
摘要:
Techniques for processing reference-based SQL/XML operators are provided. Instead of extracting copies of one or more nodes from XML data, a reference-based operator returns a reference to a node. Such a reference is used to determine, for example, whether the corresponding node comes logical before, after, or is the same as another node. An SQL/XML query that includes a reference-based operator may be the original query, or may be generated (e.g., rewritten) from a non-SQL/XML query, such as an XQuery query. One or more physical rewrites may be performed on the SQL/XML query, depending on how the XML data is stored and/or whether an XML index exists for the XML data.
摘要:
Instances of complex types are logically replicated. In general, the logical replication of complex types involves converting a complex type instance from its storage format into a logical representation written in a markup language, like XML. The logical representation is then propagated to a destination (or destinations), which converts the logical representation to a storage format used at the destination for that complex type.
摘要:
A method and apparatus for optimizing XML queries over heterogeneous XML tables is provided. A query that targets a container (e.g. table or collection) that contains a plurality of XML documents is received, wherein at least two XML documents in the plurality do not conform to the same schema. Based on the received query, a plurality of execution plans is generated. Each execution plan is associated with a different XML schema. An execution plan is used to execute the query relative to those XML documents that conform to the XML schema associated with the execution plan.
摘要:
Efficiently replicating XML data among databases includes techniques for (a) replicating XML data involved with an insert operation; (b) replicating XML data involved with an update operation; (c) leveraging existing relational replication techniques for XML data stored in shredded form using object-relational constructs; and (d) replicating XQuery Data Model sequences. Each technique reduces the amount of information that would otherwise need to be transmitted over a network for XML data replication purposes.
摘要:
A method for representing XML information is provided. A serialized image of XML information is generated. The serialized image comprises a collection of one or more serialized data values, where each particular serialized data value in the collection includes data associated with a particular serialized data value type of a plurality of serialized data value types. The serialized image may also comprise a first field that includes a first value, which indicates that the serialized image includes the collection of one or more serialized data values. In some embodiments, the method is performed at a database system that supports a native XML data type, wherein the XML information is one or more instances of the native XML data type.
摘要:
A method and apparatus for optimizing XML queries over heterogeneous XML tables is provided. A query that targets a container (e.g. table or collection) that contains a plurality of XML documents is received, wherein at least two XML documents in the plurality do not conform to the same schema. Based on the received query, a plurality of execution plans is generated. Each execution plan is associated with a different XML schema. An execution plan is used to execute the query relative to those XML documents that conform to the XML schema associated with the execution plan.
摘要:
A method and apparatus for processing queries is provided. A query is received at a mid-tier node of a multi-tier system. The mid-tier node includes a mid-tier cache that is configured to cache relational tables from one or more databases managed by a database server in a database tier of the multi-tier system. At the mid-tier node, a determination is made whether the received query includes an operator for requesting data of an XML datatype from the database server, where the XML datatype is supported as a native datatype by the database server. If a determination is made that the query includes such operator, then one or more portions of one or more relational tables are retrieved from the database server and stored in the mid-tier cache. The one or more relational tables store, in the one or more portions, index information associated with the requested data of the XML datatype. The received query is rewritten into a relational query against at least the one or more portions of the one or more relational tables that are stored in the mid-tier cache.
摘要:
XQuery queries that include functions that operate on dynamically typed XML data are rewritten into compilable SQL constructs. XML data that is dynamically typed is XML data for which a specific XML data type cannot be determined at compile time and in fact may vary. In general, XQuery queries are rewritten into SQL queries that use SQL constructs in lieu of XQuery constructs. The SQL constructs include an “SQL polymorphic function” that is defined or recognized by a database system as valid syntax for an SQL query. The rewritten query applies the XML data to the SQL polymorphic function, but the XML data has been typed as XMLType, a data type recognized by SQL standards.