How to view full blocking postgres queries?
The length of the query tracked can be found in the parameter track_activity_query_size.

18.8.1. Query and Index Statistics Collector


track_activity_query_size (integer)

  
  Specifies the number of bytes reserved to track the currently executing command for each active session, for the
  pg_stat_activity.current_query field. The default value is 1024. This
  parameter can only be set at server start.


e.g. if you had track_activity_query_size=16384 in your config, then this would mean that query text up to 16k would be collected.