There is a similar looking question asked at :
How can I shorten the URL query paramters?
But here the query parameter is single and its value is comma separated list of long Ids.
Eg. http://example.com/page?q='111100000123,111100000234,11134423213,238418249,823481293,841298472384,89234798124,981248923,24982134983'
Encode this value to something like
htp://example.com/page?q='cdw,erw,ere...'
or
htp://example.com/page?q=asfjeoren
and then decode it back at server side to original value.