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When Cardinality Statistics Are Automatically Updated

When Cardinality Statistics Are Automatically Updated

For the following operations that you perform on a table, Derby automatically creates statistics. Those operations are:

  • (new index only) When you create a new index on an existing non-empty table.
  • (new backing indexes only) When you add a primary key, unique, or foreign key constraint to an existing non-empty table.

For other operations, Derby automatically updates statistics for the table and all indexes on the table if they are already exist. Those operations are:

  • (all indexes) When you execute SYSCS_UTIL.SYSCS_COMPRESS_TABLE.
  • (index only) When you drop a column that is part of a table's index; the statistics for the affected index are dropped, and statistics for the other indexes on the table are updated.

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