MS RFC 22a: Feature cache for long running processes and query processing (Call for comments)

[Tamas Szekeres]

Developers,

Currently the various query operations involve multiple access to the
data providers may cause a significant performance impact depending on
the providers. In the first phase all of the features in the given
search area are retrieved and the index of the relevant shapes are
stored in the result cache. In the second phase the features in the
result cache are retrieved form the provider one by one. Retaining the
shapes in the memory we could eliminate the need of the subsequent
access to the providers and increase the overall performance of the
query. Implementing the cache requires a transformation of the data
between the data provider and the client. From this aspect it is
desirable to provide a framework to implement this transformation in a
higher level of abstraction.

I've modified the original concept to eliminate the need of
introducing a new category and structure type in the core mapserver.
Currenly the feature cache is being implemented as one additional data
provider which use another layer as the data source. This concept
involves linking the layers to each other.

This RFC intends to describe the general concept which can easily be
turned into a full implementation with further error handling in time
for the 5.0 release if the concept gets the required support to carry
on.

Any comments or ideas are highly appreciated.

Best regards,

Tamas