Does updating one Bokeh ColumnDataSource affect the entire document?
As of Bokeh 0.12.5 update messages are:

triggered immediately for a given property change 
granular (are not batched in any way)

So, updating model.foo triggers an immediate message sent to the browser, and that message only pertains to the corresponding model.foo in the browser. 
There Bokeh protocol allows for batching updates, but this capability is not really used anywhere yet. It is an open feature request to allow for some kind of batching that would delay sending update messages until some grouping of them could be collected.
I have a Bokeh document with many plots/models, each of which has its own ColumnDataSource.  If I update one ColumnDataSource does that trigger updates to all of my models or only to the models to which the changed source is relevant?
I ask because I have a few models, some of which are complex and change slowly and others which are simple and change quickly.  I want to know if it makes sense performance-wise to scale the update frequencies on a per-plot basis or if I have to actually have different documents for this to be effective.
I am running a Bokeh server application