摘要:
A method and system for providing convergence of data copies in asynchronous data replication in a database system, includes: labeling rows of a plurality of table copies with a monotonic number, a copy identification, and propagation controls; asynchronously capturing at least one labeled change to any row of any of the plurality of table copies from a database recovery log; determining that the captured change is to be communicated to others of the plurality of table copies; communicating the captured change to the others of the plurality of table copies; and applying the communicated change to the others of the plurality of table copies, where the plurality of table copies converge to a same state. In applying the communicated changes, conflicting changes are identified and resolved. In this manner, convergence of data copies in asynchronous data replication is provided, and processing and storage costs are significantly reduced.
摘要:
An extensible identification system for nodes in a hierarchy is described wherein each node is assigned a concatenation of decimal based values. The values assigned uniquely identify the node, provides an order for the node, and identifies its parent, child, and sibling relationships with other nodes Furthermore, the IDs assigned can be encoded to be byte comparable. Furthermore, the ID's assigned to nodes need not be modified when changes (adding/deleting a child node or a subtree of nodes) are made in the hierarchy. Additionally, in the event of such a change, the order and relationships between the parent, child, and sibling nodes are retained.
摘要:
A method for using pre-computed information stored in auxiliary structures to speed up processing of expensive queries on hierarchical documents such as XML documents being queried using XPath. The invention defines a taxonomy of such structures such as indexes and materialized views for storing pre-computed XPath results (PXRs), determines what portion of the query can be evaluated by the structures, and computes the compensation for the results generated by the structures. The invention detects all structures applicable to the query and rewrites the query to use such structures, speeding up the performance of the queries. The invention identifies the matching structures by detecting containment mappings between XPath expressions in the query and the structure. The invention also includes a new representation for XPath expressions that is rich enough to express all features of XPath.
摘要:
Provided are techniques for processing a query. The query is received, and the query is formed by one or more paths, where each path includes one or more steps. A hierarchical document is received that includes one or more document nodes. While processing the query and traversing the hierarchical document to find document nodes described by at least one of the one or more steps of the query, a match graph is constructed that includes one or more match nodes. Each of the match nodes identifies a step instance and is associated with step instances that are ancestors and descendants of the identified step instance. Also, each of the match nodes is associated with a level. In addition, the match graph includes zero or more edges between the match nodes indicating relationships between the match nodes. The match nodes in the match graph are traversed from lower levels to higher levels to construct results for the query.
摘要:
A system, method, and computer program product to improve XML query processing efficiency with virtual cursors. Structural joins are a fundamental operation in XML query processing, and substantial work exists on index-based algorithms for executing them. Two well-known index features—path indices and ancestor information—are combined in a novel way to replace at least some of the physical index cursors in a structural join with virtual cursors. The position of a virtual cursor is derived from the path and ancestor information of a physical cursor. Virtual cursors can be easily incorporated into existing structural join algorithms. By eliminating index I/O and the processing cost of handling physical inverted lists, virtual cursors can improve the performance of holistic path queries by an order of magnitude or more.
摘要:
A direct drive, single stage, centrifugal compressor air blower assembly for increasing air pressure and air flow for industrial process air applications. The blower assembly consists of a scroll-shaped, single stage, centrifugal compressor air blower housing having an air inlet and an air outlet. The centrifugal air compressor housing contains an impeller that is mounted on an end of a drive shaft of a high speed asynchronous AC induction motor shaft. The drive shaft extends from the asynchronous AC induction motor into the centrifugal compressor blower housing. The compressor blower housing is rotatably attached to the motor housing which enables the direction of the air flow to be changed without repositioning the motor. A Variable Frequency Drive (VFD) is used to control motor RPM and hence blower output. The VFD and asynchronous AC induction motor combination provides 5 to 50 horsepower over an operating RPM range of 10,000 to 30,000 RPM.
摘要:
Aircraft trailing edge devices, including devices with non-parallel motion paths, and associated methods are disclosed. A device in accordance with one embodiment includes a wing and an inboard trailing edge device coupled to the wing and movable relative to the wing between a first stowed position and a first deployed position along a first motion path. An outboard trailing edge device can be coupled to the wing outboard of the inboard trailing edge device, and can be movable relative to the wing along a second motion path that is non-parallel to the first motion path. An intermediate trailing edge device can be coupled between the inboard and outboard trailing edge devices and can be movable along a third motion path that is non-parallel to both the first and second motion paths. Each of the trailing edge devices can open a gap relative to the wing when moved to their respective deployed positions.
摘要:
An XML query compilation processor (20) includes an execution compiler (42) that transforms an XML query into an executable XML query plan (22). A query rewrite processor (34) performs query transformations on the XML query. Said query transformations include transforming an expression input (60) received by an expression (62) conditional upon a set of items defined by an output (64) of the expression (62) being independent of grouping of items in the expression input (60).
摘要:
Trailing edge devices configured to carry out multiple functions, and associated methods of use and manufacture are disclosed. An external fluid flow body (e.g., an airfoil) configured in accordance with an embodiment of the invention includes a first portion and a second portion, at least a part of the second portion being positioned aft of the first portion, with the second portion being movable relative to the first portion between a neutral position, a plurality of upward positions, and a plurality of downward positions. A guide structure can be coupled between the first and second portions, and an actuator can be operatively coupled between the first and second portions to move the second portion relative to the first portion. In one embodiment, a flexible surface can track the motion of the second portion and can expose a gap at some positions. In another embodiment, a controller can be coupled to the actuator and can be configured to direct the actuator to move the second portion to a high lift setting, a high drag setting, a roll setting, and a trim setting. In yet another embodiment, trailing edge devices on an airfoil can have scaled, mechanically similar guide structures.
摘要:
Disclosed is an evaluation technique for text search with black-box scoring functions, where it is unnecessary for the evaluation engine to maintain details of the scoring function. Included is a description of a system for dealing with blackbox searching, proofs of correctness, as well experimental evidence showing that the performance of the technique is comparable in efficiency to those techniques used in custom-built engines.