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Home -> Community -> Usenet -> c.d.o.misc -> 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
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