| 摘要 |
An index is built upon on one more columns of a database table. In order to retrieve values from the database table, a block-order scan is performed on the index by sequentially reading one or more units of contiguous blocks of the index. For a B-tree index, branch nodes in the blocks are ignored, but column values from within leaf nodes are retrieved. The column whose values are read can be determined from processing a query that references the column. The index can be partitioned so that the block-order index can be performed on only some of the index. Moreover, the block-order index scan is suitable for a table organized as an index.
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