A computer implemented method performs constrained searching of an index of a database. The information of the database is stored as a plurality of records. A unique location is assigned to each indexable portion of information of the database. Index entries are written to a memory where each index entry includes a word entry representing a unique indexable portion of information, and one or more location entries for each occurrence of the unique indexable portion information. The index entries are sorted according to a collating order of the word entries, and sequentially according to the location entries of each index entry. A query is parsed to generate a first term and a second term related by an AND logical operator, the AND operator requires that a first index entry corresponding to the first term and a second index entry corresponding to the second term both have locations in the same record to satisfy a query. The location entries of the first and second index entries are searched subject to one or more constraints which must be satisfied. The constraints are expressed as C(a).ltoreq.C(b)+K, where C(a) means a current location of the first index entry, C(b) means a current location of the second index entry, and K is a predetermined constant.
This application is a continuation of application Ser. No. 09/054,439 filed on Apr. 3, 1998, now abandoned, which is a continuation of application Ser. No. 08/694,912, filed on Aug. 9, 1996 (issued on Apr. 28, 1998 as U.S. Pat. No. 5,745,890).
This invention introduces a new concept called virtual construct intervals (VCI), where each predicate interval is decomposed into one or more of these construct intervals. These VCIs strictly cover the predicate interval. Namely, every attribute value covered by the predicate interval is also covered by at least one of the decomposed VCIs, and vice versa. Each construct interval has a unique ID or interval coordinate and a set of endpoints. A construct interval is considered activated when a predicate interval using it in its decomposition is added to the system. The predicate ID is then inserted into the ID lists associated with the decomposed VCIs. To facilitate fast search, a bitmap vector is used to indicate the activation of VCIs that cover an event value. The challenge is to find an appropriate set of construct intervals to make predicate decomposition simple and, more importantly, to build efficient bitmap indexes. Because each construct interval covers only a small range of attribute values, the invention also uses bitmap clipping to cut unnecessary bitmap storage. To facilitate bitmap clipping, the invention introduce the covering segment concept. Bit positions outside a covering segment are pruned.
An index tuning wizard produces a fast and reasonable recommendation identifying database indexes to use given a specified workload. A query optimizer is used to determine the expected usefulness of potential indexes for the specified workload by taking cost of queries in the workload into account. A cost based pruning of indexes is then performed to provide an intermediate set of proposed indexes. Indexes having most benefit based on storage constraints are then selected. The optimizer is then used again, and further pruning is done on a benefits basis. An index is not recommended unless it has a significant impact on the workload.
A method and apparatus that detects mirrored host pairs using information about a large set of pages, including URLs. The identities of the detected mirrored hosts are then saved so that browsers, crawlers, proxy servers, or the like can correctly identify mirrored web sites. The described embodiments of the present invention look at the URLs of pages hosts to determine whether the hosts are potentially mirrored.
A method and system that detects mirrored host pairs using information about a large set of pages, including one or more of: URLs, IP addresses, and connectivity information. The identities of the detected mirrored hosts are then saved so that browsers, crawlers, proxy servers, or the like can correctly identify mirrored web sites. The described embodiments of the present invention use one or a combination of techniques to identify mirrors. A first group of techniques involves determining mirrors based on URLs and information about connectivity (i.e., hyperlinks) between pages. A second group of techniques looks at connectivity information at a higher granularity, considering all links from all pages on a host as one group and ignoring the target of each link beyond the host level.
A method is provided for tuning a database to recommend a set of physical design structures for the database that optimize database performance for a given workload given a total time bound that defines a maximum amount of time that can be spent tuning the database. A cumulative set of recommended structures is maintained and incrementally updated based on tuning that is performed in intervals over portions of the workload. The cumulative set of recommended structures is updated by tuning the database by examining a predetermined portion of the workload during a time slice that is a fraction of the total time bound. At the end of the time slice, a set of recommended structures has been enumerated that is based on the workload portions that have been examined thus far. The set of recommended structures is updated until all queries in the workload have been examined or until the time bound is reached.
