Execution of snapshot statements can lead to unexpected transaction conflicts in write-intensive workloads

Detail name	Value
Changelog Number	10098
Type	Bug
Status	Resolved
Affected Versions
Fix Versions	Exasol 7.0.0, Exasol 6.2.7, Exasol 6.1.10
Resolution Date	2020-06-08

Description

The execution of snapshot statements was introduced so that front-end tools can retrieve Exasol metadata without locking database objects in order to avoid transaction conflicts. During the execution of those snapshot statements, the transaction management system must prevent object versions from being deleted prematurely.

Due to a bug, this protection mechanism could lead to unexpected transaction conflicts, especially during write-intensive workloads.

Workaround

Retrying the query after the sessions have committed without snapshot mode should not result in this unexpected conflict anymore. Please note that sessions without snapshot mode can run into other transaction conflicts, as described here: https://www.exasol.com/portal/display/SOL/Transactions

Fix

Using Snapshot Mode will no longer cause unexpected transaction conflicts