When we've had the need to cache a query, we just throw the result (as a DOM object) into the sesssion. I'm including the sample pipeline. I'll typicailly aggregate the results of this with something else (usually a dynamic query) and I'm all set. When I want to clear the cache, the session attribute can be cleared.
(note, the getUserIdAction is something we wrote to grab the logged in user out of the session. We use container based authentication, but stash an object in the session for use in the sitemap).
We also ended up writing an action to invalidate a sesion object (used to clear the cache).
<map:pipeline internal-only="true">
<map:match pattern="assoc-list">
<map:act type="getUserIdAction">
<map:select type="sessionAttributeExists">
<map:parameter name="attribute-name" value="assoc-cache"/>
<map:when test="true">
<map:generate type="session-attr">
<map:parameter name="attr-name" value="assoc-cache"/>
</map:generate>
<map:serialize type="xml"/>
</map:when>
<map:otherwise>
<map:generate src="xml/assoc_query.xml"/>
<map:transform type="sql">
<map:parameter name="use-connection" value="mbrdb"/>
<map:parameter name="userid" value="{userid}"/>
</map:transform>
<map:transform type="writeDOMsession">
<map:parameter name="dom-name" value="assoc-cache"/>
<map:parameter name="dom-root-element" value="page"/>
</map:transform>
<map:serialize type="xml"/>
</map:otherwise>
</map:select>
</map:act>
</map:match>David
Christian Kurz wrote:
I just skimmed through the mailing list to find ideas of how to cache a pipeline starting with a request generator and later on passing data through the SQLTransformer.
Did you or anybody else follow up on this idea?
NB: Caching of the request generator would probably also need to cache request parameters passed not part as part of the URL. As usually only some request parameters are used in the pipeline, the sitemap element might list the request parameters to consider when generating cache key:
<map:generator type="request"> <map:parameter name="request-data-used" value="input1"> <map:parameter name="request-data-used" value="input2"> ...
-------------------------------------------------
A couple of things I'd like to do with Cocoon caching; let me know if this is crazy.
1. Add caching to the request generator. Many of my pipelines are transformations based upon the request, and since requestGenerator currently does not support caching, it means those transformations are always re-done (and often there is some sql at the end of the pipe which is really slow). I'd like to hash (or MD5?) the request string and use that as the cache key so that if I get the same one the pipeline knows it can skip over everything.
2. Add caching to the SqlTransformer. I know this sounds weird, but hear me out. Our database is modified infrequently, so usually returns the same data. There is a datestamp in a special table which indicates when the last time the database was updated. The SQL Transformer would remember the time of the last query. I would have a new parameter to the sql transformer to indicate when the data is dirty.
<map:transform type="sql"> <map:parameter name="last-update-time" value="cocoon:/lastUpdateTime.xml"/> </map:transform>
LastUpdateTime looks like:
<Date>20021005144321</Date> (Or whatever the xml date format is, I forget).
SQLGenerator would resolve cocoon:/lastUpdateTime.xml.
I would then have a pipeline for lastUpdateTime.xml which would build it by querying my special table (but if you wanted, you could use some other mechanism to build it).
SQLGenerator would compare the two dates and re-run the sql if it needed to.
How does this sound?
Steve
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