[MCOL-1398] MariaDB CS returns wrong values if query_cache_size is turned on Created: 2018-05-08  Updated: 2022-11-05  Resolved: 2022-11-05

Status: Closed
Project: MariaDB ColumnStore
Component/s: MariaDB Server
Affects Version/s: 1.1.4
Fix Version/s: Icebox

Type: Bug Priority: Major
Reporter: Johanna Neumann Assignee: Unassigned
Resolution: Won't Do Votes: 0
Labels: None


 Description   

If you turn on the "query_cache_size" in a MariaDB Columnstore installation, the SELECT Statements will return wrong values.

The first query will return the correct values, but after that every select query returns the values from the first (cached) query.
For Example:
Select * from A;
-> return A
Select * from B;
-> return A;
Select * from B;
-> return A;
[...]

Disconnecting does not help, since the cache remains. After the cache is invalidated (e.g. after a reboot) only the first query is correct again.
If you turn off the query cache everything works like a charm again.

Tested with version 1.1.3 and 1.1.4

 Comments   
Comment by Andrew Hutchings (Inactive) [ 2018-05-08 ]

First of all I'd highly recommend not turning on Query Cache with ColumnStore, especially in a multi-UM system.

Some questions for you:
1. Are you using infinidb_vtable_mode of 1 when executing these queries?
2. Are tables A and B ColumnStore tables?

Comment by Johanna Neumann [ 2018-05-08 ]

Hi Andrew,
we now turned it off in all our columnstore systems. It was part of our standard configuration for mariadb, we now built a seperate configuration.

1. yes, "infinidb_vtable_mode=1"
2. We tested both, it doesnt' matter, both columnstore and both innodb are returning the same wrong results.

Thank you!

Comment by Todd Stoffel (Inactive) [ 2022-11-05 ]

This item is being closed because it was well passed the expiration date with no activity. If you suspect this was done in error please create a new ticket.

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