Re: exp: why have statistics=estimate option?

 "WS(> From: "Lun Wing San (Oracle)" <wslun_at_qrcsun.qrc.org>

 "WS(> Chuck Hamilton wrote:
>
> Maybe this is a dumb question, but why even have the
> 'statistics=estimate' option in the export utility? When a table gets
> imported, the _exact_ number of rows imported is already available.
> Why not just use that number to populate DBA_TABLES.NUM_ROWS instead
> of going through the time consuming process of issuing an ANALYZE
> TABLE command?

Perhaps because the exact number of rows imported isn't available until they've been imported?

"Statistics are not recorded in the export file, only a command to generate them." This is just allowing you keep the statistics on the newly imported data as you did before they were exported.

Not a dumb question, you just missed the fact that some installations want the system after the import to look like the system before the import.

 "WS(>   ANALYZE can help you to populate the statistics 
 "WS(> information into DBA_TABLES, 
 "WS(> DBA_INDEXES, DBA_TAB_COLUMNS, INDEX_STAT, 
 "WS(> INDEX_HISTOGRAMS. By using these statistics, 
 "WS(> you can carry out cost-based optimization in the 
 "WS(> execution of a DML if OPTIMIZER_GOAL 
 "WS(> is set to CHOOSE, ALL_ROWS or FIRST_ROWS.

That did not answer his question.

jg Received on Thu Jan 02 1997 - 00:00:00 CST