observe_export_resource_data/2
mod_export - fetch a row for the export, can return a list of rows, a binary, and optionally a continuation state. Where Values is [ term() \], i.e. a list of opaque values, to be formatted with #export_resource_format. Return the empty list of values to signify the end of the data stream.
Type:
Return:
{ok, Values|binary()}
, {ok, Values|binary(), ContinuationState}
or {error, Reason}
#export_resource_data{}
properties:
dispatch:
atom
id:
m_rsc:resource_id()|undefined
content_type:
binary
state:
term