MERGE INTO a zonemapped column can lead to wrong results in filtering
Details
| Detail name | Value |
|---|---|
| Changelog Number | 20386 |
| Type | Bug |
| Status | Resolved |
| Affected Versions | Exasol 8.26.0 |
| Fix Versions | Exasol 8.27.0 |
| Resolution Date | 2024-05-02 |
Description
“MERGE INTO” SQL queries modifying columns that use the Zonemaps feature may store incorrect zonemap metadata depending on system race conditions. This can lead to wrong results in filtering when using the affected columns.
One can verify if a column is using Zonemaps with the following queries:
SELECT COLUMN_NAME, COLUMN_IS_ZONEMAPPED FROM EXA_ALL_COLUMNS WHERE COLUMN_TABLE = 'my_table';
or
DESCRIBE my_table;
Workaround
Disable zonemaps for the affected column(s). Optionally, if the zonemap is enabled again, it will be populated with correct metadata.
drop zonemap on MY_TABLE (MY_COLUMN); --optionally enforce zonemap on MY_TABLE (MY_COLUMN);
Fix
In these circumstances, zonemaps won’t get corrupted.
