摘要:
Partially materialized views in the field of database systems are described herein. A method of partially materializing a view computed from one or more source tables comprises generating a view definition including a query expression and at least one control predicate referencing at least one control table. The query expression specifies the maximal content of the view, that is, the complete set of records that could be materialized. One or more control predicates and the contents of one or more control tables restrict what records are actually materialized and stored in the view. This allows the content of the partially materialized view to be adjusted simply by updating one or more control tables.
摘要:
A transformation-based optimizer generates rewritings by applying local algebraic transformation rules on subexpressions of a query. Application of a transformation rule produces substitute expressions, logically equivalent to the original expression. View matching, that is, computing a subexpression from materialized views, is one such transformation rule. The view matching rule applies a view matching technique that determines whether the original query can be computed from one or more of the existing materialized views and, if so, generates substitute expressions. An index structure of materialized views is provided that quickly narrows the search to a set of candidate views on which the view matching techniques can be applied. The index structure, also called a filter tree, speeds up the search for applicable materialized views.
摘要:
Currency and consistency requirements are specified as part of a query against a database that may contain replicated data that is updated asynchronously and therefore may not be completely up to date. The database system constructs query execution plans that include an input selection operator that verifies the currency of a replica and selects a subplan using the replica for execution only when the replica meets the query's currency constraints. It checks possible query execution plans at construction time against the query's consistency constraints and any plans that may produce a result not meeting the consistency constraints are rejected. In this way, the query result is guaranteed to satisfy the query's currency and consistency requirements.
摘要:
A transformation-based optimizer generates rewritings by applying local algebraic transformation rules on subexpressions of a query. Application of a transformation rule produces substitute expressions, logically equivalent to the original expression. View matching, that is, computing a subexpression from materialized views, is one such transformation rule. The view matching rule applies a view matching technique that determines whether the original query can be computed from one or more of the existing materialized views and, if so, generates substitute expressions. An index structure of materialized views is provided that quickly narrows the search to a set of candidate views on which the view matching techniques can be applied. The index structure, also called a filter tree, speeds up the search for applicable materialized views.
摘要:
A transformation-based optimizer generates rewritings by applying local algebraic transformation rules on subexpressions of a query. Application of a transformation rule produces substitute expressions, logically equivalent to the original expression. View matching, that is, computing a subexpression from materialized views, is one such transformation rule. The view matching rule applies a view matching technique that determines whether the original query can be computed from one or more of the existing materialized views and, if so, generates substitute expressions. An index structure of materialized views is provided that quickly narrows the search to a set of candidate views on which the view matching techniques can be applied. The index structure, also called a filter tree, speeds up the search for applicable materialized views.
摘要:
Methods, systems, and computer-readable media are disclosed for time-based event processing using punctuation events. A particular method includes receiving a first event object comprising a first validity start time and a first validity end time, where the first validity end time is initially undefined. A punctuation object is received after the first event object. The punctuation event object has a punctuation timestamp indicating a time subsequent to the first validity start time. The punctuation event object indicates that event objects to be received at the computer system after the punctuation event object have validity start times later than the time indicated by the punctuation timestamp. The method includes setting the first validity end time to a value later than or equal to the time indicated by the punctuation timestamp.
摘要:
A controllable drug delivery device for delivering a liquid injectable drug, the device comprising a drug reservoir (22), a drug administration device (28), a displacement-generating battery (20), and a current-depletion circuit (85), wherein displacement generated by the battery as current is depleted from the battery by the current depletion circuit displaces a wall of the drug reservoir thereby causing the reservoir to expel liquid injectable drug contained therein via the drug administration device, and wherein the drug delivery device further includes a controller (78) that is responsive to a measured parameter indicative of displacement generated by the battery for applying a variable load (80) across the battery in order to provide a substantially constant-current depletion of the battery and thereby cause the drug delivery device to deliver a substantially constant drug delivery rate.
摘要:
A “Query Optimizer” provides a cost estimation metric referred to as “Maximum Accumulated Overload” (MAO). MAO is approximately equivalent to maximum system latency in a data stream management system (DSMS). Consequently, MAO is directly relevant for use in optimizing latencies in real-time streaming applications running multiple continuous queries (CQs) over high data-rate event sources. In various embodiments, the Query Optimizer computes MAO given knowledge of original operator statistics, including “operator selectivity” and “cycles/event” in combination with an expected event arrival workload. Beyond use in query optimization to minimize worst-case latency, MAO is useful for addressing problems including admission control, system provisioning, user latency reporting, operator placements (in a multi-node environment), etc. In addition, MAO, as a surrogate for worst-case latency, is generally applicable beyond streaming systems, to any queue-based workflow system with control over the scheduling strategy.
摘要:
The invention provides a solid phase hydrogen-generating system utilizing a solid chemical hydride fuel selected from the group consisting of sodium borohydride, lithium borohydride, magnesium hydride and calcium hydride, wherein the fuel is encapsulated in a plurality of removable capsules, the capsules being pumpable and having a major axis of up to 40 mm.
摘要:
A method, system and product for delivering a postal mailpiece to a recipient address. A registration based mail-addressing protocol is utilized that allows a postal recipient to create and maintain a proxy address, which is dynamically associated with the recipient's postal address and is more simple than the postal address. The sender of a postal mailpiece addresses the mailpiece with the simplified proxy address instead of the burdensome recipient postal address. The method, system and product allows recipients to create and manage proxy addresses, detects a proxy address on a mailpiece and takes the appropriate measures to deliver the postal mailpiece to a physical address corresponding recipient postal address.