Unnessary index creations for complex queries on big tables
Details
| Detail name | Value |
|---|---|
| Changelog Number | 8522 |
| Type | Bug |
| Status | Resolved |
| Affected Versions | Exasol 6.1.0, Exasol 6.2.0 |
| Fix Versions | Exasol 7.0.0, Exasol 6.1.7, Exasol 6.2.2 |
| Resolution Date | 2019-08-12 |
Background
To save compile time for complex queries (nested views, WITH clauses) the optimizer does not apply every optimization step to all parts of the query plan. Especially expensive optimizations like join ordering and index-related optimizations are avoided.
Problem Description
Some index-related optimizations may be executed too often which leads to an increase in compile time and possibly to the creation of additional indices that were not needed in the final query plan.
Workaround
Once the additional indices are committed, the affected query will not create them anymore and run faster. However, the system will drop the additional unused indices after a few weeks.
