Re: Performance improvement proposal. Removal of toLowerCase calls.

Hi Dave,

On 16/01/14 16:12, Dave Cramer wrote:
> Jeremy.
>
> I am even wondering why we would be doing that and even worse using a
> locale to do it.
>
I suspect it's caters for when the request SQL is mixed case. To get a
match from the db server the response SQL (as you say is lower case)
you'd need to make sure the .put(...) on the registry is either all
upper or lower.
> AFAICT, the db would return everything in lower case anyway, and if
> the column really had mixed case it should be returned with it's
> original case intact.
Shall I prepare a PR with a test case ?

Jeremy
>
> Dave
>
> Dave Cramer
>
> dave.cramer(at)credativ(dot)ca
> http://www.credativ.ca
>
>
> On Thu, Jan 16, 2014 at 10:44 AM, Jeremy Whiting <jwhiting(at)redhat(dot)com
> <mailto:jwhiting(at)redhat(dot)com>> wrote:
>
> Hi,
> I would like to propose an optimization to improve performance in the
> jdbc driver. The performance improvement has been tested on commodity
> hardware using an industry standard Java benchmark. The overall
> benchmark metric reports an improvement in performance. Profiling
> using
> sampling showed calls reduced from 1100 to 0 when the benchmark
> workload
> is running.
>
> The optimization will eliminate calls to the method
> toLowerCase(java.util.Locale). This in the pg-jdbc
> org.postgresql.jdbc2.AbstractJdbc2ResultSet.findColumnIndex(java.lang.String)
> method when setting up the column index registry.
>
> For the optimization to be enabled I suggest relying on a new system
> property. Making the existing functionality the default behaviour to
> ensure existing applications do not break when the driver is upgraded.
>
> The change removes the call toLowerCase when putting items in the
> registry [1]. Essentially what's being proposed is removing
> sanitizing
> the key names. For best performance application code should pass
> SQL to
> the driver with column names already folded to lower case. But upper
> case names will still be matched in the second lookup [2] in the
> method.
> For this optimization to work this feature introduces a
> requirement on
> applications. To use all lower or upper case column names.
>
> Are there other factors that might affect this optimization that need
> to be taken into consideration ?
>
> Regards,
> Jeremy Whiting
>
> Senior Software Engineer
> Red Hat
>
> [1]
> https://github.com/pgjdbc/pgjdbc/blob/REL9_3_STABLE/org/postgresql/jdbc2/AbstractJdbc2ResultSet.java?#L2742
> [2]
> https://github.com/pgjdbc/pgjdbc/blob/REL9_3_STABLE/org/postgresql/jdbc2/AbstractJdbc2ResultSet.java?#L2752
>
>
>
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