Improved compile time in some DML operations
Details
| Detail name | Value |
|---|---|
| Changelog Number | 11203 |
| Type | Improvement |
| Status | Resolved |
| Fix Versions | Exasol 7.1.0 |
| Resolution Date | 2021-08-03 |
Background
Exasol database automatically computes and stores column statistics on demand, e.g. when joining tables for the first time. Those statistics consist of distinct estimates, minimum & maximum values, balancing, and other information. They are used by our query optimizer for estimation of join costs, filter sensitivities, etc.
The computation of column statistics is a compute-intensive operation. Therefore, they are maintained as part of DML statements. If a significant amount of data has been changed since the last computation a recalculation is triggered.
Improvement
DML compile time is improved if the following conditions are met:
- A DML statement is executed
- Data resides on HDD
- Recalculation of column statistics is triggered
This improvement can be identified by a reduced time in COMPILE/EXECUTE.
