db_file_multiblock_read_count = 32 実行計画 ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=35 Card=1 Bytes=13) 1 0 SORT (AGGREGATE) 2 1 TABLE ACCESS (FULL) OF 'T1' (TABLE) (Cost=35 Card=9872 Bytes=128336) db_file_multiblock_read_count = 16 実行計画 ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=39 Card=1 Bytes=13) 1 0 SORT (AGGREGATE) 2 1 TABLE ACCESS (FULL) OF 'T1' (TABLE) (Cost=39 Card=9872 Bytes=128336) db_file_multiblock_read_count = 8 実行計画 ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=48 Card=1 Bytes=13) 1 0 SORT (AGGREGATE) 2 1 TABLE ACCESS (FULL) OF 'T1' (TABLE) (Cost=48 Card=9872 Bytes=128336) db_file_multiblock_read_count = 4 実行計画 ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=66 Card=1 Bytes=13) 1 0 SORT (AGGREGATE) 2 1 TABLE ACCESS (FULL) OF 'T1' (TABLE) (Cost=66 Card=9872 Bytes=128336)
db_file_multiblock_read_count 对cost的影响
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转载自hudingchen.iteye.com/blog/1379117
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