| Sizing indexes [message #53269] |
Tue, 10 September 2002 06:52  |
Lee Ming Soon
Messages: 6
Registered: August 2002
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Junior Member |
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How to estimate index size?
Example:
Table A
Column Datatype Index
====== ======== =====
col1 Varchar2(19) PK
col2 Date PK
col3 Varchar2(10) Yes
col4 Number(2) No
col5 Number(13,2) Yes
What would be the estimate (or max) size for one row of data (based on the database design)?
Thanks!!
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| Re: Sizing indexes [message #53277 is a reply to message #53269] |
Tue, 10 September 2002 14:01  |
andrew again
Messages: 2577
Registered: March 2000
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Senior Member |
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select vsize(rowid) + vsize(sysdate) + vsize('hello world')... from dual;
It's not very accurate as you need to cater for the overhead. As the index gets many inserts/deletes/updates it does grow in size even if the number of rows in the table is the same. Don't try to squeeze the whole index into a single extent - many extents are fine. Try to make extent sizes for all extents in the TS the same to avoid fragmentation.
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