[postgis-users] MapServer PostgreSQL and persistent databaseconnections

[Paul Ramsey]

Hi Jan,
Sorry, I really do not know. Oracle is multi-threaded, so it is not like 
they have to start a new backend for every new process.
Paul

Jan Hartmann wrote:
> Paul, do you know WHY Oracle / SDE have such long connection times, 
> compared to PostgreSQL? Is there some added functionality/bookkeeping 
> invoved?
> 
> Jan
> 
> Paul Ramsey wrote:
> 
>>   The eternal question, to connection pool or not to connection pool. :)
>> The reason why connection pooling is considered an important problem 
>> for enterprise application developers is... because Oracle is really 
>> slow at establishing a connection. Really, that is why! PostgreSQL 
>> connections times are inconsequential. In the context of a process as 
>> computationally intensive as Mapserver, PgSQL connections times might 
>> as well be considered to be zero.
>>   This gets discussed every month or so on the Mapserver list, and the 
>> bottom line is that 99% of your processing time for a given map 
>> creation will be spent retrieving and rendering the data. Connection 
>> time for PostgreSQL is completely ignorable in term of impact on 
>> system load.   For Oracle and ArcSDE, connection time is non-trivial, 
>> and that is a problem.
>>   Because there are some connection time issues with some of the 
>> backends, for Mapserver 4.0 there has been an enhancement to ensure 
>> that database connections are pooled PER MAPPING INVOCATION. So within 
>> a particular instantiation of the mapserv CGI, only one connection to 
>> each database is used. So if I have 15 ArcSDE layers in my map, I will 
>> only connect ONCE, not 15 times.
>>   The infrastructure of inter-layer connection pooling exists in 
>> Mapserver 4.0, and has been implemented on ArcSDE connections only, so 
>> far, but is completely reusable for OracleSpatial and PgSQL layers. 
>> The implementation for those layers just needs to be done.
>>
>> Yours,
>> Paul
>>



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      | Paul Ramsey
      | Refractions Research
      | Email: pramsey at refractions.net
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