Bug #15314 SHOW queries are slower in 5.0 than in 4.1

• Submitted: 29 Nov 2005 14:42
• Modified: 27 Sep 2008 14:39
• Reporter: Alexey Kopytov
• Status: Won't fix
• Category: Server: I_S
• Severity: S5 (Performance)
• Version: 5.0.13
• OS: Any
• Assigned to: Sergey Gluhov
• Tags: affects_connectors

[29 Nov 2005 14:42] Alexey Kopytov

Description:
This is a followup to bug #13931.  Below are the average numbers of queries per second
over 3 benchmark runs:

4.1.14:
SHOW VARIABLES: 1785.06 
SHOW COLLATIONS: 1674.99

5.0.13:
SHOW VARIABLES: 807.50
SHOW COLLATIONS: 1086.73

Looking at the source code, 4.1 tree uses Protocal::store to store the results of SHOW
queries, while 5.0 stores them in a temporary table using Field_*::store method, which is
more expensive. This also means that all other SHOW queries are slower in 5.0.

How to repeat:
Benchmark the performance of SHOW queries in 4.1 and 5.0

[27 Sep 2008 14:39] Konstantin Osipov

This was an intentional change to make sure SHOW queries use information_schema
implementation, I doubt that we have any plans to fix this, apart from re-implementing
information_schema.