The space overhead for the ROWID is 10 bytes for 2-byte partitioning and 16 bytes for 8-byte partitioning.
The following equation provides an estimate of the space overhead required for a row-compressed join index. Double the result if you define fallback on the index.
Row-compressed join index size = U × (F + O + (R × A))
where:
| Symbol | Description | |||
|---|---|---|---|---|
| F | Length of the fixed column column_name. | |||
| R | Length of a single repeating column column_name. | |||
| A | Average number of repeated columns for a given value in column_1_name. | |||
| U | Number of unique values in the specified column_1_name | |||
| O | Row overhead. Assume the following row overhead for a join index:
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