摘要:
Maintenance of materialized view for query optimization in a database. The architecture provides the first practical algorithms for incrementally maintaining views with multiple outer joins and aggregated outer-join views. Materialized views with any combination of inner joins, one-sided outer joins and full outer joins, plus an optional aggregation on top, can be processed by algorithm(s) that construct incremental maintenance expressions based on converting the view definition a join-disjunctive normal form and exploiting database constraints to reduce maintenance overhead. A system comprises a view creation component for creating a materialized view definition that includes outer-joins, a conversion component for converting an outer-join view expression into a normal form, and a maintenance component for updating the stored materialized view result associated with the materialized view definition.
摘要:
A materialized XML view matching system and method for processing of SQLXML queries using view matching of materialized XML views. The view matching process of the embodiments of the system and method use a multi-path tree (MPT) data structure. Embodiments of the materialized XML view matching system and method construct an MPT data structure for each input query and view expression. View matching is performed on the MPT data structures to generate a set of partial matches, which then are cleaned to generate a set of candidate matches. A valid match definition is generated by testing each candidate match for different forms of compliance. Using the valid match definition, a set of valid matches is identified and extracted. For each valid match, a substitute query expression is constructed that can serve as a replacement for the original query. These substitute queries can be used to evaluate the original query.
摘要:
This disclosure provides techniques for asynchronously maintaining database indexes or sub-indexes. For example, a database management server may receive a data manipulation statement to modify particular data stored in a database and determine whether an index associated with executing the statement is maintained asynchronously. When the index is maintained asynchronously, maintenance of the index to reflect changes made to the particular data by executing the data manipulation statement may be delayed until an index maintenance event. The index maintenance may be based on an isolation level of a transaction including a query that triggered the index maintenance.
摘要:
A system for optimizing queries against a database is described. The system comprises a memo structure that encodes a plurality of query expressions. The system also includes a signature mechanism that enables an assignment of the query expressions into equivalence classes. Methods of using such a system are additionally provided.
摘要:
A system and method that facilitates and effectuates estimating the result of performing a data analysis operation on a set of data. Employing an approximation of the data analysis operation on a statistically valid random sample view of the data allows for a statistically accurate estimate of the result to be obtained. Sequential sampling in the view enables the approximated operation to evaluate accuracy conditions at intervals during the scan of the sample view and obtain the estimated result without having to scan the entire sample view. Feedback regarding the accuracy of the estimated result can be captured when the data analysis operation is performed against the set of data. Process control techniques can be employed with the feedback to maintain the statistical validity of the sample view.
摘要:
Parameterized queries are optimized by a transformational optimizer. The optimizer produces a dynamic plan that embeds multiple plan options that may be selected to execute a particular query. Parameter distribution improves query execution efficiency and performance by exploring a sample parameter space representative of the parameter values actually used. The dynamic plans can be simplified while maintaining an acceptable level of optimality by reducing the number of plan options. The reduction is achieved by eliminating switch unions to alternatives that are close in cost. Both approaches of parameter space exploration and dynamic plan generation are deeply integrated into the query optimizer.
摘要:
A materialized XML view matching system and method for processing of SQLXML queries using view matching of materialized XML views. The view matching process of the embodiments of the system and method use a multi-path tree (MPT) data structure. Embodiments of the materialized XML view matching system and method construct an MPT data structure for each input query and view expression. View matching is performed on the MPT data structures to generate a set of partial matches, which then are cleaned to generate a set of candidate matches. A valid match definition is generated by testing each candidate match for different forms of compliance. Using the valid match definition, a set of valid matches is identified and extracted. For each valid match, a substitute query expression is constructed that can serve as a replacement for the original query. These substitute queries can be used to evaluate the original query.
摘要:
This disclosure provides techniques for asynchronously maintaining database indexes or sub-indexes. For example, a database management server may receive a data manipulation statement to modify particular data stored in a database and determine whether an index associated with executing the statement is maintained asynchronously. When the index is maintained asynchronously, maintenance of the index to reflect changes made to the particular data by executing the data manipulation statement may be delayed until an index maintenance event. The index maintenance may be based on an isolation level of a transaction including a query that triggered the index maintenance.
摘要:
Methods and systems for integrating use of materialized transient views into generation of an optimized query execution plan. Features and aspects hereof provide rapid identification of common expressions in a query as transient view candidates and then rapidly select among the transient view candidates for those transient views that most benefit the cost of execution of the query. The selected transient views are incorporated into a generated final, optimized query execution plan including operator to materialize the selected transient views for re-use in execution of the query.
摘要:
A system for optimizing queries against a database is disclosed. The system comprises a memo structure that encodes a plurality of query expressions. The system also includes a signature mechanism that enables an assignment of the query expressions into equivalence classes. Methods of using such a system are additionally provided.