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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Insert Cardinalities into the data dictionary directly
Thanks for the feedback, I am coming from the Oracle Rdb world, where these row counts/cardinialities could be inserted into the data dictionary to simulate the optimizer behaviour similar to a production environment.
I see your point, this could be a negative impact to the optimizer.
Thanks for the input.]
Murali
Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
Date: Wed, 18 Apr 2001 09:15:23 -0800
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
ian_at_slac.stanford.edu
-----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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Author: Murali Vallath
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Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Liststo: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Wed Apr 18 2001 - 14:30:16 CDT
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