I'm thinking caching byte arrays on a per-connection basis is the way to
go.
However, how much difference do you expect this to make? How many byte
arrays to you allocate and destroy per SQL statement? And how big are
the arrays? How much memory will they occupy per open connection?
Will this really make a big difference?
- Keith
-----Original Message-----
From: Gunnar R|nning <gunnar@candleweb.no>
To: Keith L. Musser <kmusser@idisys.com>
Cc: Gunnar R|nning <gunnar@candleweb.no>; PGSQL-General
<pgsql-general@postgresql.org>
Date: Friday, September 29, 2000 12:39 PM
Subject: Re: [GENERAL] Re: JDBC Performance
>[feel stupid replying to myself...]
>
>Gunnar R|nning <gunnar@candleweb.no> writes:
>
>> > at org.postgresql.jdbc2.ResultSet.getObject(ResultSet.java:789)
>>
>> OK, I found the problem. I will post a fixed version later today. The
>> problem was that getObject() executed Field.getSQLType() which in
turn
>> executed Connection.ExecSQL(). I modified ExecSQL to deallocate the
cached
>> byte arrays on entry, because I believed it only were called by
>> Statement.execute() methods. I guess I should move the deallocation
into
>> the Statement classes instead, as that is were it really belongs.
>>
>> I interpret the JDBC spec. to say that only one ResultSet will be
open
>> per. Statement, but one Connection canm have several statements with
one
>> result set each.
>>
>
>This does of course imply that arrays should be cached on a
>ResultSet/Statement basis instead of on PGStream as it is done now. Do
>anybody have good suggestions on how to implement this ?
>
>Approach 1:
>The cache is now only per Connection, maybe we should a global pool of
free
>byte arrays instead ?
>Cons :
>This would probably mean that we need to add more
>synchronization to ensure safe access by concurrent threads and could
>therefore lead to poorer performance and concurrency.
>
>Pros : Possibly lower memory consumption and higher performance in some
>cases(when you find free byte arrays in the global pool). If your
>application is not pooling connections, but recreating connections it
would
>also benefit performance wise from this approach.
>
>Approach 2:
>Another solution would be have the cache be per connection but
associate a
>pool of used byte arrays to each resultset/statement and deallocate
these
>on resultset.close()/statement.close().
>
>Pros: Faster for the typical web application that uses pooled
connections,
>because this approach would require less synchronization.
>Cons: Higher memory consumption.
>
>Either of these two approaches would probably require some
reorganization
>of how the driver works.
>
>Any other suggestions or comments ?
>
>
>Regards,
>
> Gunnar
>
