摘要:
According to an embodiment of the present invention, a method for reorganizing a source index tree of a database table resulting in a target index tree of the database table is provided. A backup process reads source leaf pages of the source index tree in a logical order defined by a sequence of index keys. The logical order can be different from a physical order of the source leaf pages defined by a sequence of respective storage locations. The backup process constructs target leaf pages of the target index tree maintaining the logical order. A restore process constructs target non-leaf pages of the target index tree based on the distribution of the index keys among the constructed leaf pages and stores the target leaf and non-leaf pages.
摘要:
According to one embodiment of the present invention, a method for identifying relevant database indexes is provided. According to one embodiment of the present invention, a method includes determining the importance of a particular database transaction and storing an index name related to the transaction along with an indicator of the importance. A database transaction is initiated and the importance indicator is received in an index advisor. The index advisor then makes an index recommendation based on the index importance.
摘要:
According to an embodiment of the present invention, a method for reorganizing a source index tree of a database table resulting in a target index tree of the database table is provided. A backup process reads source leaf pages of the source index tree in a logical order defined by a sequence of index keys. The logical order can be different from a physical order of the source leaf pages defined by a sequence of respective storage locations. The backup process constructs target leaf pages of the target index tree maintaining the logical order. A restore process constructs target non-leaf pages of the target index tree based on the distribution of the index keys among the constructed leaf pages and stores the target leaf and non-leaf pages.
摘要:
Presented is a method to perform a query to retrieve data from a database that is part of a computer system comprising a Data-Base Management System (DBMS) with an optimizer. A Query Execution Plan (QEP) is generated for the query. The QEP is assessed by considering statistical values about previous executions of the query according to the QEP to decide whether to choose the QEP or to generate a new QEP. Furthermore, the statistical values on previous executions of the query are exploited during query optimization. The query is executed according to the chosen QEP. For optimizing the execution of future queries, statistical values about the execution of the query are collected during execution.
摘要:
The present invention proposes enhancing the access path selection process by storing the relevant frequency distribution and the host variables values used for selecting the access path together with the corresponding access path executable. This way, the host variables impact to the access path can be inexpensively assessed and the re-optimization triggered only if necessary.
摘要:
A method of searching a data page in a table space of a database for inserting a data record to a first table, wherein the table space comprises space map pages and sets of data pages, wherein each space map page comprises information about the available storage space of one set of data pages, wherein each space map page and the corresponding set of data pages is further assigned to a table range for each table to which at least one data page in the set of data pages belongs to, wherein the database further comprises a clustering index for the first table in the database management system, wherein the database management system comprises a space usage information database, and wherein the space usage information database holds space usage information for each table range.
摘要:
Embodiments of the present invention provide a “look-ahead” form prefetch. Look-ahead prefetch may utilize a look-ahead queue to prefetch multiple pages asynchronously. The look-ahead queue may hold a plurality of search keys that are related to a transaction. When accessing a table, an index manager may retrieve the table's index and scan the index based on the search keys from the look-ahead queue to find the RIDs in the table that match the search keys. The index manager may then accumulate these RIDs into a prefetch list. A prefetch manager may read the prefetch list, determine locations for the pages of the table that contain the records identified by the RIDs, and dispatch prefetch tasks to the appropriate storage device for these pages.
摘要:
A computer implemented method is provided for processing data representing a data entity having sub entities. The method includes analyzing queries to the data entity for deriving information about sets of the sub entities frequently queried together, and grouping the sub entities to a number of banks, each bank having a maximum width, based on the information about sets of sub entities frequently queried together, in order to reduce an average number of banks to be accessed for data retrieval.
摘要:
A method for generating occurrence data of data values for enabling encoding of a data set includes determining occurrences of data values in a first data batch and determining occurrence count information for a first number of most frequent data values in the first data batch, the occurrence count information identifying the most frequent data values and their occurrence counts. The method also includes generating for rest of the data values in the first data batch at least a first histogram having a second number of buckets and merging the occurrence count information of the first data batch with occurrence count information of a second data batch. The method further includes merging the first histogram of the first data batch to a merged histogram corresponding to the second data batch and processing a next data batch as a first data batch until the data set to be encoded is processed.
摘要:
A mechanism is provided for reorganizing a source index tree of a database table resulting in a target index tree of the database table is provided. A backup process reads source leaf pages of the source index tree in a logical order defined by a sequence of index keys. The logical order can be different from a physical order of the source leaf pages defined by a sequence of respective storage locations. The backup process constructs target leaf pages of the target index tree maintaining the logical order. A restore process constructs target non-leaf pages of the target index tree based on the distribution of the index keys among the constructed leaf pages and stores the target leaf and non-leaf pages.