One of interesting uses of this feature is creation of statistics for
temporary tables which cannot be done otherwise. It is Tom Kite's idea.
Alex Hillman
-----Original Message-----
Sent: Wednesday, April 18, 2001 1:15 PM
To: Multiple recipients of list ORACLE-L
Take a look at dbms_stats.set_column_stats and dbms_stats.set_table_stats.
The latter allows you to
set the number of rows, the size of the table and such ; the first allows
you to set the number of distinct values for a column the number of nulls,
etc.
I'm not sure what you are trying to accomplish with this. Is simply
changing the cardinalities of a the columns enough? What about the
distribution of those values? If the changes result in a different query
path, and your queries run more slowly, does that mean they will do so when
the statistics truly reflect the database. Perhaps they are running more
slowly because you lied to the optimizer.
"I am aware that if this is was an environment with good cardinalities,
these
values could be exported and imported into another environment."
Cardinality reflects the ratio of distinct values to the total number of
values in the database.
I can think of scenarios where cardinality might change significantly for a
time. But I would think in most cases it would remain fairly constant.
FYI, if statements which assert something contrary to fact are subjunctive
not conditional.
"If this WERE an environment with good cardinalities...."
Ian MacGregor
Stanford Linear Accelerator Center
[EMAIL PROTECTED]
-----Original Message-----
Sent: Wednesday, April 18, 2001 8:06 AM
To: Multiple recipients of list ORACLE-L
I am trying again
------
To obtain a good analysis of a SQL statement especially in a new development
environment, based on the environment that it is to be deployed on, it would
good to sometime reflect/simulate the production volume.
Is there a way to input table cardinalities directly into the data
dictionary so that the Optimizer could be made to act like in production.
I am aware that if this is was an environment with good cardinalities, these
values could be exported and imported into another environment.
My question is this possible from scratch?
Regards,
Murali Vallath
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