Saturday, 15 January 2011

query analyzer - How Oracle uses statistics data -


I got a comment about Oracle's data:

Oracle does not know that 50M Of course, there are figures in the number of rows, but they can be old and wrong - and Oracle does not allow itself to give wrong results because only the figures are wrong

I'm pretty sure That's up to Oracle, while preparing the query execution plan. Recommendations were made to refresh the data periodically before version 10 and the statistics were automatically collected from 10 grams Oracle.

Can anyone tell if the Oracle query analyzer depends on the data figures? Oracle figures too much to generate

query execution schemes What does this (and not) do, uses those data in a manner that affects the query result , which you were trying to do with "ROWNUM & lt; 50000000" Statistics may be outdated, or may be unavailable. However, this would mean that Oracle may slow down in producing the right result, it does not mean that Oracle will return the wrong result.

If Oracle had your expectation, then it could be decided that "ROWNUM & lt; 50000000" means "get all the rows" even though the table now has 60,000,000 rows 49,000,000). Fortunately this does not happen


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