The <histogramstatistics> database configuration element

The <tablestatistics> element in database-config.xml has several subelements, one of which is the <histogramstatistics> element. By default, PolicyCenter issues a single dbms_stats.gather_table_stats(... 'FOR COLUMNS ...') statement for all columns of interest in the table, including:

  • All columns that are the first key column of an index. (Oracle only).
  • The retired column, if present.
  • The subtype column, if present.
  • All columns that have the createhistogram attribute set to true. (Guidewire sets this value internally.)
The <histogramstatistics> element has the following format:
  • <histogramstatistics name="string" numbuckets="integer" />

The name attribute specifies a column name. The numbuckets attribute controls the maximum number of buckets for the specified histogram. Guidewire requires that you provide a value for this attribute. The default value for the number of buckets is 254.

Performance notes

  • For performance reasons, PolicyCenter does not currently create a histogram on publicid columns. These columns are rarely, if ever, referenced in a WHERE clause.
  • Also for performance reasons, PolicyCenter tries to combine as many columns as possible into a single statement. Certain tabs in the Database Catalog Statistics page display a dbms_stats.gather_table_stats(...'FOR COLUMNS ...') statement with only the associated column for each histogram, regardless of the parameter values. This enables you to specify the most granular statement if a given histogram is out of date.