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ZIM Object Dictionary

Field BWSel

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Index selectivity factors. Index selectivity factors used by Zim’s strategy optimizer.

Valid Values

A number from 0 to 1.000 (DEFAULT = 1.000)


The index selectivity factors are relevant for indexed fields only.

Each number represents the fraction of records that you would typically expect to retrieve using an indexed lookup with a particular operator or operators.


selectivity factor for BETWEEN


selectivity factor for the equals (=) operator


selectivity factor for all other operators (i.e., less than (<), greater than (>), less than or equals (<=), greater than or equals (>=))

Values closer to 0 imply a very selective index, while values closer to 1 imply an index with poor selectivity. A value of 1.000 instructs Zim to use its internal selectivity factors.

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