Abstract: Conditional functionality is provided for database merge operations. A merge operation, for merging data from a source to a destination, involves performing a default operation for each source record. Default operations associated with a MERGE statement include UPDATE and INSERT operations. Which default operation is performed depends on whether any destination record corresponds to a given source record. In an embodiment, whether a specified condition is satisfied is determined. If the condition is satisfied, then the default operation that is appropriate for a given source record is performed. If the condition is not satisfied, then the given source record is processed without performing the appropriate default operation. In one aspect, the UPDATE clause of the MERGE statement is extended to include a conditional DELETE clause.

Abstract: According to one aspect, an index that is built on a table having a plurality of rows comprises an index entry that contains a key value for a sub-part of a row and that includes data for locating a row and data for locating, within the row, a value associated with the sub-part of the row. In one embodiment, the sub-part of the row is an array, with each member of the array represented in the row.

Abstract: Methods are provided for efficiently evaluating database queries including a rollup operator and a distinct aggregate function. Using a sequence of sorts, duplicate record elimination performed on previous sorts at lower, or finer, levels of the rollup operator is taken advantage of by performing subsequent sorts on the preceding sort. Hence, when moving from one rollup level to the next higher level, there are fewer data records to sort with respect to the relevant grouping columns for that level, and thus also fewer duplicate data records to eliminate for purposes of computing the distinct aggregate. Using parallel evaluation, processing of aggregate functions is split among different processing slaves, and the measure of an aggregate function is included as a partitioning key when sending data from one data flow operation to the next data flow operation of a query execution plan.

Abstract: Methods are provided for efficiently evaluating database queries that include a grouping sets specification, by reducing the grouping sets specification to one or more combinations of groupings that are computable with simple GROUP BY clauses, with or without a rollup operator, wherein the GROUP BY clauses and rollup operators are efficient operations that can be computed with a single data sort. Computational costs are further minimized by computing a grouping from records generated from computation of a previously computed grouping. An optimization algorithm is described which determines the respective grouping combinations to which the grouping sets specification is reduced and the respective GROUP BY clauses, to minimize computational costs. Furthermore, an intermediate grouping, that is, a grouping that is not specified by the query, is included in a query evaluation plan in some instances, to compute specified groupings when doing so reduces computational costs.

Abstract: Techniques for optimizing a distributed lock manager (DLM) for faster reconfiguration includes using a constant hash function to associate each resource of a plurality of shared resources with a hash value. A hash map is maintained which associates a plurality of hash value ranges with each of one or more master nodes. In response to one or more factors, the hash value ranges are re-mapped to master nodes by revising the hash map without changing the constant hash function. The factors include at least a measure of the amount of lock information or a weight. A weight is associated with each node in the cluster, and is selected from a set of non-uniform master weights.

Abstract: Techniques are provided for delivering search results pages to the users of a search engine, where one or more search result listings on the search results pages include items that are not included by default. The non-default items may take many forms, including but not limited to images, banners, controls, animations, and even Java applets. The non-default items may be designed to entice the search engine users to select the search result listing with which they are associated over possibly higher-ranked search result listings that contain only default items.

Abstract: Techniques are provided which address the problems associated with the conventional approaches for storing multidimensional data in a relational database system. According to technique, the many foreign key values of each row in the fact table are mapped to and replaced by a “replacement” value. A mapping function is provided that derives a replacement value from any given combination of foreign key values, and an inverse mapping function is provided to reproduce the combination of foreign key values given the replacement value. A mapping function is selected such that the foreign key value combinations of multidimensional values that are conceptually related to each other map to values that are close to each other. The rows in the fact table are then stored within the fact table in the sorted order, thus causing values that are conceptually related to each other to be stored physically near each other within the fact table.

Abstract: A method and mechanism are provided for creating, maintaining, and using a hierarchical index to efficiently access information in a relational system based on a pathnames, thus emulating a hierarchically organized system. Each item that has any children in the emulated hierarchical system has an index entry in the index. The index entries in the index are linked together in a way that reflects the hierarchical relationship between the items associated with the index entries. Pathname resolution is performed by following direct links between the index entries associated with the items in a pathname, according to the sequence of the filenames within the pathname. By using an index whose index entries are linked in this manner, the process of accessing the items based on their pathnames is significantly accelerated, and the number of disk accesses performed during that process is significantly reduced.

Abstract: Techniques are provided for updating data that logically resides in one or more nested collections in a nested collection column of a view. According to one technique, a Data Manipulation Language (DML) statement that operates on individual elements within the one or more nested collections is detected. Instead of executing the DML statement, trigger code is executed once for each individual element, within the one or more nested collections, that is targeted by the DML statement. In addition, the trigger code may include one or more references to parent values. For each nested collection selected by the DML statement, the following steps are performed when the trigger code includes references to parent values: determining the row, within the view, in which the nested collection resides and, prior to executing the trigger code for the nested collection, binding the one or more references to one or more corresponding values that logically reside in the row.

Abstract: Techniques are provided which address the problems associated with the conventional approaches for storing multidimensional data in a relational database system. According to technique, the many foreign key values of each row in the fact table are mapped to and replaced by a “replacement” value. A mapping function is provided that derives a replacement value from any given combination of foreign key values, and an inverse mapping function is provided to reproduce the combination of foreign key values given the replacement value. A mapping function is selected such that the foreign key value combinations of multidimensional values that are conceptually related to each other map to values that are close to each other. The rows in the fact table are then stored within the fact table in the sorted order, thus causing values that are conceptually related to each other to be stored physically near each other within the fact table.

Abstract: A method and mechanism are provided for creating, maintaining, and using a hierarchical index to efficiently access information in a relational system based on a pathnames, thus emulating a hierarchically organized system. Each item that has any children in the emulated hierarchical system has an index entry in the index. The index entries in the index are linked together in a way that reflects the hierarchical relationship between the items associated with the index entries. Pathname resolution is performed by following direct links between the index entries associated with the items in a pathname, according to the sequence of the filenames within the pathname. By using an index whose index entries are linked in this manner, the process of accessing the items based on their pathnames is significantly accelerated, and the number of disk accesses performed during that process is significantly reduced.