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Rows in Sort order without order by clause?

I have been asked by one of colleague (Vasu) about a weird issue, that the query returns rows in sort order  in one database not in the other database.

Without having much hassle, by running dbms_xplan.display_cursor('sql_id',NULL,'ADVANCED) mode tell's us the optimizer parameter "_gby_hash_aggregation_enabled" is having different values in each database. Which is mean to perform the sort group by or hash group by operation.

To simulate the issue, I just did the following, a quick check on v$session row_wait_obj# column with parameter false/true.

The result show rows in non sorted for true, (means performed a hash group by operation) where in with false the rows are in sorted order (sort group by has been performed)




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