摘要:
A method and apparatus for merging synopses to determine a database statistic, e.g., a number of distinct values (NDV), is disclosed. The merging can be used to determine an initial database statistic or to perform incremental statistics maintenance. For example, each synopsis can pertain to a different partition, such that merging the synopses generates a global statistic. When performing incremental maintenance, only those synopses whose partitions have changed need to be updated. Each synopsis contains domain values that summarize the statistic. However, the synopses may initially contain domain values that are not compatible with each other. Prior to merging the synopses the domain values in each synopsis is made compatible with the domain values in the other synopses. The adjustment is made such that each synopsis represents the same range of domain values, in one embodiment. After “compatible synopses” are formed, the synopses are merged by taking the union of the compatible synopses.
摘要:
Techniques for proactively and reactively running diagnostic functions. These diagnostic functions help to improve diagnostics of conditions detected in a monitored system and to limit/quarantine the damages caused by the detected conditions. In one embodiment, a health monitor infrastructure is provided that is configured to perform one or more health checks in a monitored system for diagnosing and/or gathering information related to the system. The one or more health checks may be invoked pro-actively on a scheduled basis, reactively in response to a condition detected in the system, or may even be invoked manually by a user such as a system administrator.
摘要:
A method and apparatus for approximating a database statistic, such as the number of distinct values (NDV) is provided. To approximate the NDV for a portion of a table, a synopsis of distinct values is constructed. Each value in the portion is mapped to a domain of values. The mapping function is implemented with a uniform hash function, in one embodiment. If the resultant domain value does not exist in the synopsis, the domain value is added to the synopsis. If the synopsis reaches its capacity, a portion of the domain values are discarded from the synopsis. The statistic is approximated based on the number (N) of domain values in the synopsis and the portion of the domain that is represented in the synopsis relative to the size of the domain.
摘要:
One or more usage models are provided for a database. Each usage model includes a set of rules that are used to analyze database performance. A usage model in one or more usage models is determined. Database information is determined based on the usage model. The database information is then analyzed based on rules associated with the usage model. One or more performance problems are determined based on the analysis.
摘要:
A unified database/text retrieval system converts exact database type queries into text inclusion type queries suitable for text retrieval systems through the use of pseudo keywords. Boolean combination of the text inclusion type query elements may be readily manipulated for optimization and applied to a unified index for rapid search results. Absolute relevance values and relevance multiplier values may be added to the query elements to provide a relevance-based sorting not only of text but also of exact match type search results. Relevance values may be deduced automatically from a variety of sources.