Merging database log files through log transformations
First Claim
1. A method for constructing a global equivalent database log file using at least two local log files in a parallel or distributed database system comprising the steps of:
- creating, from each local log file, a list of log entries associated with a database record;
separating said list of log entries associated with said each local log file into list segments;
performing actions on said list segments, said actions selected from the group consisting of reducing the number of said list segments and shortening said list segments; and
merging remaining list segments into a second list.
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Abstract
A method to construct a global equivalent database log file that transforms local log files from a parallel or distributed database system by extracting from each log file sequences of log entries from each database record, breaking the sequences into a series of segments, discarding the bulk of the segments and shortening other segments, then merging the remaining segments into an equivalent log file. The sequences are called "UID-sequences" and the segments "UID-segments" because they relate to one unique record ID or UID. The method also employs backward and forward superposition to further shorten the segments. This method works on database systems with or without instant constraint checks and also provides for treating log entries from multiple adjacent transactions on a log file as a single transaction. In systems with instant constraint checks, this method performs a "unique-key check" and a "foreign-key check" and resolves conflicts that are created because of superposition.
122 Citations
28 Claims
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1. A method for constructing a global equivalent database log file using at least two local log files in a parallel or distributed database system comprising the steps of:
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creating, from each local log file, a list of log entries associated with a database record; separating said list of log entries associated with said each local log file into list segments; performing actions on said list segments, said actions selected from the group consisting of reducing the number of said list segments and shortening said list segments; and merging remaining list segments into a second list. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for constructing a global equivalent database log file using at least two local log files in a parallel or distributed database system comprising the step of treating multiple adjacent transactions in a local log file as one transaction.
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24. A method for constructing a list of update operations within a global equivalent log file that adheres to constraints placed on a database system using at least two local log files comprising the steps of:
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placing a first update operation after a second update operation if said first update operation appears after said second update operation in a first local log file; placing said first update operation before said second update operation if said update operations do not appear in the same local log file and if a constraint would be violated were said first update operation to be placed after said second update operation, provided that update operations from said first local log file appearing after said second update operation in said list of update operations are repositioned in said list of update operations to appear before said first update operation; and comparing update operations appearing in said list of update operations after said second update operation to ensure that no constraint is violated if said first update operation is placed before said second update operation. - View Dependent Claims (25, 26, 27, 28)
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Specification