[MDEV-3997] Querying a Cassandra table on a server with query cache enabled is likely to cause problems Created: 2013-01-04 Updated: 2014-10-01 Resolved: 2013-02-04 |
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| Status: | Closed |
| Project: | MariaDB Server |
| Component/s: | Storage Engine - Cassandra |
| Affects Version/s: | 10.0.1 |
| Fix Version/s: | 10.0.2 |
| Type: | Bug | Priority: | Minor |
| Reporter: | Elena Stepanova | Assignee: | Sergei Petrunia |
| Resolution: | Fixed | Votes: | 0 |
| Labels: | cassandra | ||
| Issue Links: |
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| Description |
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Since Cassandra is by nature a shared storage which can be accessed (and modified) through different Cassandra SE tables, doing it from a server where query cache is enabled is likely to produce wrong results. Of course, the workaround is to use SQL_NO_CACHE in a query, but it's error-prone. Besides, generally a user would have no way to know whether the storage gets updated or not, so they'll have to set SQL_NO_CACHE every time; and if so, it makes sense to either force disabling query cache for Cassandra tables, or to provide a system-wide parameter for doing so. Example of the problem:
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| Comments |
| Comment by Sergei Petrunia [ 2013-01-10 ] |
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Discussed with Sanja: it seems, query cache should be disabled for cassandra tables. This can be achieved like this: ha_cassandra::table_cache_type() { return HA_CACHE_TBL_NOCACHE; } |
| Comment by Sergei Petrunia [ 2013-02-04 ] |
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Disabled query cache for cassandra tables. |