| Bug #39845 | Falcon: Concurrent online DROP INDEX causes assertion | ||
|---|---|---|---|
| Submitted: | 3 Oct 2008 23:53 | Modified: | 9 Jan 2009 14:10 |
| Reporter: | Christopher Powers | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: Falcon storage engine | Severity: | S1 (Critical) |
| Version: | 6.07 | OS: | Any |
| Assigned to: | Christopher Powers | CPU Architecture: | Any |
| Tags: | F_ONLINE ALTER | ||
[3 Oct 2008 23:55]
Christopher Powers
Verified during debugging of Bug#39795, "Falcon: Online add index does not support index with non-null columns"
[3 Oct 2008 23:59]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/commits/55298 2852 Christopher Powers 2008-10-03 Bug#39845, "Falcon: Concurrent online DROP INDEX causes assertion"
[9 Jan 2009 14:10]
MC Brown
A note has been added to the 6.0.8 changelog: When performing an online DROP INDEX on a Falcon table, the operation may conflict with other index operations such as including index scans. When one client drops an index, another client may initiate a concurrent index operation that accesses the mapping object of the index being dropped, and this can cause a crash
Description: The concurrent online alter stress test, falcon_online_alter, causes a fatal assertion in Index::makeKey(). Table::rollbackRecord() cycles through the indexes to clean up unused keys. The assertion occurs if the rollback accesses an index that had just been dropped. The assertion implies that indexId == -1, however, in some cases, the debugger shows indexId to have a normal value, suggesting an A-B-A condition. Transaction::rollback() RecordVersion::rollback() Table::rollbackRecord() Table::garbageCollect() Index::garbageCollect(Record *leaving, *staying) { for (record = leaving to staying) { ... IndexKey key(this); makeKey(record, &key); Index::makeKey(...) { ASSERT (indexId != -1); ... } How to repeat: 1. Install random query generator: https://inside.mysql.com/wiki/QARandomQueryGenerationTutorial 2. Run SystemQA falcon_online_alter runall.pl --basedir=<mysql directory> \ --engine=Falcon \ --grammar=conf/falcon_online_alter.yy \ --threads=10 \ --queries=100000 Suggested fix: A shared Table lock in Table::rollbackRecord() prevents the assert. The larger question is whether all concurrent operations are sufficiently protected from online drop index (Falcon does not support online drop column.)