Compression anomaly for string columns
Details
| Detail name | Value |
|---|---|
| Changelog Number | 16033 |
| Type | Bug |
| Status | Resolved |
| Affected Versions | Exasol 7.0.0, Exasol 7.1.0 |
| Fix Versions | Exasol 8.9.0, Exasol 7.1.17 |
| Resolution Date | 2023-01-12 |
Description
In some rare cases, a compression anomaly may cause CHAR() and VARCHAR() columns to use more space than expected. In these cases, the MEM_OBJECT_SIZE for the affected columns in EXA_DBA_COLUMN_SIZES is larger than expected. In some cases, it is even larger than the RAW_OBJECT_SIZE.
Workaround
Run a RECOMPRESS on the affected tables and columns with the ENFORCE option. For example:
RECOMPRESS TABLE MYTAB (STRING_COL_1, STRING_COL_2) ENFORCE;
Fix
Affected CHAR() and VARCHAR() columns are compressed as expected and the overall MEM_OBJECT_SIZE for columns affected by this bug is reduced.
