| Re: Index size [message #50202] |
Tue, 05 March 2002 21:39 |
andrew again
Messages: 2577
Registered: March 2000
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Senior Member |
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Don't try to be too accurate. See Oracle documentation on DATATYPES. Number is a varying length datatype. Your index will contain your NUMBER data as it exists in the table and a corresponding ROWID.
http://www-rohan.sdsu.edu/doc/oracle/server803/A54641_01/apa.htm
If you create an index on one of your tables, then:
analyze table XYZ estimate statistics;
Now, select index_name, num_rows, avg_row_len from user_indexes where table_name = 'XYZ';
That's the easy way to determine the row length. Remember that after a while, the index grows due to insets, updates and deletes even if the number of rows remains constant. Don't fall into the trap of constantly trying to rebuild indexes to shrink them unless space is critical. In data warehouses space estimates are important because space used is so big.
Don't worry too much about the number of extents your tables, indexes grow to - Oracle says that up to 1000 extents per segments is nothing to worry about.
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