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create index with PARALLEL option 原理

上一篇 / 下一篇 2008-07-10 12:51:44 / 个人分类：ORACLE--特性汇总

CREATE INDEX indx_name ON schema.table_name(column_name) PARALLEL n;

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The table is randomly sampled and a set of index keys is found that equally divides the index into the same number of pieces as the specified degree of parallelism. A first set of query processes scans the table ,extracts key,row ID pairs,and sends each pair to a process in a second set of query processes based on key.Each process in the second set sorts the keys and builds an index in the usual fashion.After all index pieces are built,the parallel coordinator concatenates the pieces (whice are ordered) to form. the final index.