Updating Statistics on Specific Columns

Creating statistics on unindexed columns can improve the performance of many queries. Adding statistics for the minor columns of indexes and for unindexed columns that are frequently used in search arguments can greatly improve the optimizer’s estimates.

  1. In the Administration Console view, select ASE Servers > Schema Objects > Tables > User Tables.
  2. Click the Name field of the table, then click the drop-down arrow and select Properties.
  3. In the left pane, click Columns.
  4. Click the Name field of the column, then click the drop-down arrow and select Update Statistics.
  5. (Optional) On the Data Partitions screen of the Update Statistics wizard, select Specify a data partition, if applicable, and indicate any data partitions. update statistics runs on all partitions if you do not specify one.
  6. On the Hashing screen, select:
    • The type of hashing:
      • Partial hashing – for columns that have 65536 or fewer unique values.
      • With hashing – for columns that have more than 65536 unique values.
      • No hashing.
    • A value for max resource granularity (which indicates the maximum percentage of the system’s resources a query can use), if applicable.
  7. On the Histogram Tuning screen, set the histogram tuning factor. The size of the histogram is established by multiplying the number of steps with the value for histogram tuning factor.
  8. On the Sampling screen, specify whether to set sampling, and to what percentage.
  9. On the Step Number screen, indicate whether to set the number of histogram steps. If applicable, enter the number.
  10. On the Consumers screen, set the number of consumer processes to be used in parallel processing. The controls are enabled if the value for max parallel degree is 3 or greater.
  11. On the Datachange Threshold screen, indicate whether to run update statistics when it reaches a data change threshold, and if so, the value of the threshold.
  12. On the Summary screen, verify your selections.
  13. Click Finish.