Methods for Generating Statistics
You can generate database statistics using any of the following methods:
• optimizedb command
• CREATE STATISTICS statement
• WITH STATISTICS option of the COPY FROM command
• Using Director or VDBA
• (Beta version) Let Ingres do it automatically, as described in Automatic Histogram Generation.
(Beta Version) Automatic Histogram Generation
Ingres can automatically construct histograms from live data. After a server is started, the histograms are added as required, but left in cache for later reuse.
Histograms are automatically generated only for those columns that do not already have histograms stored in the catalog.
A typical use strategy is to create histograms (with optimizedb or CREATE STATS) for columns whose distribution does not change, and then let Ingres generate the new histograms on the other, more dynamic, columns for every server cycle.
Alternatively, if you do not want to use optimizedb or CREATE STATS, you can simply let Ingres automatically build histograms on all columns.
This feature is controlled by the opf_autostats DBMS Server configuration parameter setting in config.dat.
Last modified date: 08/28/2024