ASA SQL Reference
System Tables
| Column name | Column type | Column constraint | Table constraints |
|---|---|---|---|
| table_id | UNSIGNED INT | NOT NULL | Primary key |
| column_id | UNSIGNED INT | NOT NULL | Primary key |
| format_id | SMALL INT | NOT NULL | |
| update_time | TIMESTAMP | NOT NULL | |
| density | FLOAT | NOT NULL | |
| max_steps | SMALL INT | NOT NULL | |
| actual_steps | SMALL INT | NOT NULL | |
| step_values | LONG BINARY | ||
| frequencies | LONG BINARY |
This table stores the column statistics that are stored as histograms and used by the optimizer. The contents of this table are best retrieved using the sa_get_histogram stored procedure.
table_id A number that uniquely identifies the table or view to which this column belongs.
column_id A number that uniquely identifies the column.
format_id Internal field used to determine the format of the rest of the row.
update_time The time of the last update of this row.
density An estimate of the weighted average selectivity of a single value for the column, not counting the selectivity of large single value selectivities stored in the row.
max_steps The maximum number of steps allowed in the histogram.
actual_steps The number of steps actually used at this time.
step_values Boundary values of the histogram steps.
frequencies Selectivities of histogram steps.