Maximum number of bytes in report exceeded - API do_query

It may only be 7809 records but how many fields are being returned?  Try to limit the fields being returned by the query.  Include a clist parameter and just add fields ids you need to bring back in the query.

ie.

clist=3.4.5.6.7

Thank you for your reply
I select 60 columns, but I need them all

I just ran into this problem as well with a report that only has 4 fields but over 120K records. If you are using the API to download it you can create a loop that keeps track of how many records you are downloading at a time and use API_DoQueryCount as well as the API_DoQuery options "num-n.skip-n" to paginate your way through the records like this sudo code below:

maxRecords = {API_DoQueryCount}  retrievedRecords = 0  recordChunk = 1000  myCSV = path\to\csv  tempRecords = ""
while (retrievedRecords < maxRecords)  tempRecords = API_DoQuery&query="yourQuery"&options=num-{recordChunk}.skip-{retrievedRecords}      myCSV += tempRecords      retrievedRecords += 1000  

While the example above is over simplified and leaves out any conversion process of changing the XML into CSV I think it gives you a starting idea of how it can be done.