In Roxie, graphs execute on a single Roxie server node unless the ALLNODES() function is used. ALLNODES() causes the portion of the query it encloses to execute on all agent nodes in parallel. The results are calculated independently on each node then merged together, without ordering the records. It is generally used to do some complex remote processing which only requires local index access, substantially reducing the network traffic between the nodes.

By default, everything within the ALLNODES() will be executed on all the nodes, but sometimes the ALLNODES() query requires some input or arguments that shouldn't be executed on all the nodes--for example, the previous best guess at the results, or some information controlling the parallel query. The THISNODE() function can be used to surround element that are to be evaluated by the current node instead.

A typical usage would look like this:

bestSearchResults := ALLNODES(doRemoteSearch(THISNODE(searchWords),THISNODE(previousResults)))

Where 'searchWords' and 'previousResults' are effectively calculated on the current node, and then passed as parameters to each instance of the doRemoteSearch() executing in parallel on all nodes.