In our setup we would like to have total traffic statistics for a switch. This is something very important to us, because these statistics might indicate a bigger issue that isn't noticeable on individual traffic statistics.

To accomplish this we have to add all traffic stat items of the applicable ports in a calculated item. It seems however that there is a maximum length in the formula field for a calculated item. The formula is accepted by the frontend and API, but the items become unsupported with the following messages:

2916:20120217:102745.550 item [stub-tel-220.ams-ix.net:testcust[all,bits,out]] became not supported: Format error or unsupported operator. Exp: [last("if[24]
2918:20120217:101244.067 item [stub-tel-220.ams-ix.net:testcust[all,bits,in]] became not supported: Format error or unsupported operator. Exp: [la]

You can see that is is a maximum number characters somewhere and not the actual number of items, because the formula is cut off in different places for the different calculated items. [if[x/x],bits,in] can hold more items, because it key length is one character less than [if[x/x,bits,out]. It seems there is a limit at 2048 characters.

Original formulas:

+last("if[7/1,bits,out]")+last("if[22/7,bits,out]")+last("if[2/1,bits,out]")+last("if[19/2,bits,out]")+last("if[7/2,bits,out]")+last("if[3/1,bits,out]")+last("if[3/3,bits,out]")+last("if[19/3,bits,out]")+last("if[8/3,bits,out]")+last("if[1/4,bits,out]")+last("if[8/1,bits,out]")+last("if[3/4,bits,out]")+last("if[8/2,bits,out]")+last("if[2/2,bits,out]")+last("if[24/5,bits,out]")+last("if[21/3,bits,out]")+last("if[24/2,bits,out]")+last("if[19/6,bits,out]")+last("if[22/3,bits,out]")+last("if[5/2,bits,out]")+last("if[17/1,bits,out]")+last("if[17/2,bits,out]")+last("if[17/4,bits,out]")+last("if[17/7,bits,out]")+last("if[20/6,bits,out]")+last("if[17/5,bits,out]")+last("if[21/1,bits,out]")+last("if[22/5,bits,out]")+last("if[17/6,bits,out]")+last("if[19/1,bits,out]")+last("if[17/3,bits,out]")+last("if[20/1,bits,out]")+last("if[18/5,bits,out]")+last("if[23/8,bits,out]")+last("if[18/8,bits,out]")+last("if[24/6,bits,out]")+last("if[18/6,bits,out]")+last("if[18/7,bits,out]")+last("if[21/8,bits,out]")+last("if[6/1,bits,out]")+last("if[2/4,bits,out]")+last("if[23/6,bits,out]")+last("if[22/8,bits,out]")+last("if[1/1,bits,out]")+last("if[1/2,bits,out]")+last("if[9/1,bits,out]")+last("if[3/2,bits,out]")+last("if[4/4,bits,out]")+last("if[4/2,bits,out]")+last("if[5/1,bits,out]")+last("if[5/4,bits,out]")+last("if[6/2,bits,out]")+last("if[6/3,bits,out]")+last("if[7/3,bits,out]")+last("if[8/4,bits,out]")+last("if[21/2,bits,out]")+last("if[21/4,bits,out]")+last("if[21/7,bits,out]")+last("if[20/8,bits,out]")+last("if[22/2,bits,out]")+last("if[22/4,bits,out]")+last("if[24/1,bits,out]")+last("if[22/6,bits,out]")+last("if[17/8,bits,out]")+last("if[19/5,bits,out]")+last("if[18/4,bits,out]")+last("if[19/4,bits,out]")+last("if[19/7,bits,out]")+last("if[20/2,bits,out]")+last("if[6/4,bits,out]")+last("if[24/4,bits,out]")+last("if[20/3,bits,out]")+last("if[20/4,bits,out]")+last("if[23/3,bits,out]")+last("if[23/5,bits,out]")+last("if[7/4,bits,out]")+last("if[18/1,bits,out]")+last("if[5/3,bits,out]")+last("if[4/1,bits,out]")+last("if[24/7,bits,out]")+last("if[18/2,bits,out]")+last("if[24/8,bits,out]")+last("if[23/7,bits,out]")+last("if[21/6,bits,out]")+last("if[23/1,bits,out]")+last("if[23/2,bits,out]")+last("if[18/3,bits,out]")+last("if[22/1,bits,out]")+last("if[4/3,bits,out]")+last("if[2/3,bits,out]")+last("if[1/3,bits,out]")+last("if[19/8,bits,out]")+last("if[9/4,bits,out]")+last("if[9/5,bits,out]")+last("if[9/2,bits,out]")+last("if[9/3,bits,out]")+last("if[23/4,bits,out]")
Characters: 2485

+last("if[7/1,bits,in]")+last("if[22/7,bits,in]")+last("if[2/1,bits,in]")+last("if[19/2,bits,in]")+last("if[7/2,bits,in]")+last("if[3/1,bits,in]")+last("if[3/3,bits,in]")+last("if[19/3,bits,in]")+last("if[8/3,bits,in]")+last("if[1/4,bits,in]")+last("if[8/1,bits,in]")+last("if[3/4,bits,in]")+last("if[8/2,bits,in]")+last("if[2/2,bits,in]")+last("if[24/5,bits,in]")+last("if[21/3,bits,in]")+last("if[24/2,bits,in]")+last("if[19/6,bits,in]")+last("if[22/3,bits,in]")+last("if[5/2,bits,in]")+last("if[17/1,bits,in]")+last("if[17/2,bits,in]")+last("if[17/4,bits,in]")+last("if[17/7,bits,in]")+last("if[20/6,bits,in]")+last("if[17/5,bits,in]")+last("if[21/1,bits,in]")+last("if[22/5,bits,in]")+last("if[17/6,bits,in]")+last("if[19/1,bits,in]")+last("if[17/3,bits,in]")+last("if[20/1,bits,in]")+last("if[18/5,bits,in]")+last("if[23/8,bits,in]")+last("if[18/8,bits,in]")+last("if[24/6,bits,in]")+last("if[18/6,bits,in]")+last("if[18/7,bits,in]")+last("if[21/8,bits,in]")+last("if[6/1,bits,in]")+last("if[2/4,bits,in]")+last("if[23/6,bits,in]")+last("if[22/8,bits,in]")+last("if[1/1,bits,in]")+last("if[1/2,bits,in]")+last("if[9/1,bits,in]")+last("if[3/2,bits,in]")+last("if[4/4,bits,in]")+last("if[4/2,bits,in]")+last("if[5/1,bits,in]")+last("if[5/4,bits,in]")+last("if[6/2,bits,in]")+last("if[6/3,bits,in]")+last("if[7/3,bits,in]")+last("if[8/4,bits,in]")+last("if[21/2,bits,in]")+last("if[21/4,bits,in]")+last("if[21/7,bits,in]")+last("if[20/8,bits,in]")+last("if[22/2,bits,in]")+last("if[22/4,bits,in]")+last("if[24/1,bits,in]")+last("if[22/6,bits,in]")+last("if[17/8,bits,in]")+last("if[19/5,bits,in]")+last("if[18/4,bits,in]")+last("if[19/4,bits,in]")+last("if[19/7,bits,in]")+last("if[20/2,bits,in]")+last("if[6/4,bits,in]")+last("if[24/4,bits,in]")+last("if[20/3,bits,in]")+last("if[20/4,bits,in]")+last("if[23/3,bits,in]")+last("if[23/5,bits,in]")+last("if[7/4,bits,in]")+last("if[18/1,bits,in]")+last("if[5/3,bits,in]")+last("if[4/1,bits,in]")+last("if[24/7,bits,in]")+last("if[18/2,bits,in]")+last("if[24/8,bits,in]")+last("if[23/7,bits,in]")+last("if[21/6,bits,in]")+last("if[23/1,bits,in]")+last("if[23/2,bits,in]")+last("if[18/3,bits,in]")+last("if[22/1,bits,in]")+last("if[4/3,bits,in]")+last("if[2/3,bits,in]")+last("if[1/3,bits,in]")+last("if[19/8,bits,in]")+last("if[9/4,bits,in]")+last("if[9/5,bits,in]")+last("if[9/2,bits,in]")+last("if[9/3,bits,in]")+last("if[23/4,bits,in]")
Characters: 2388

Working formulas (made a bit shorter)

+last("if[7/1,bits,out]")+last("if[22/7,bits,out]")+last("if[2/1,bits,out]")+last("if[19/2,bits,out]")+last("if[7/2,bits,out]")+last("if[3/1,bits,out]")+last("if[3/3,bits,out]")+last("if[19/3,bits,out]")+last("if[8/3,bits,out]")+last("if[1/4,bits,out]")+last("if[8/1,bits,out]")+last("if[3/4,bits,out]")+last("if[8/2,bits,out]")+last("if[2/2,bits,out]")+last("if[24/5,bits,out]")+last("if[21/3,bits,out]")+last("if[24/2,bits,out]")+last("if[19/6,bits,out]")+last("if[22/3,bits,out]")+last("if[5/2,bits,out]")+last("if[17/1,bits,out]")+last("if[17/2,bits,out]")+last("if[17/4,bits,out]")+last("if[17/7,bits,out]")+last("if[20/6,bits,out]")+last("if[17/5,bits,out]")+last("if[21/1,bits,out]")+last("if[22/5,bits,out]")+last("if[17/6,bits,out]")+last("if[19/1,bits,out]")+last("if[17/3,bits,out]")+last("if[20/1,bits,out]")+last("if[18/5,bits,out]")+last("if[23/8,bits,out]")+last("if[18/8,bits,out]")+last("if[24/6,bits,out]")+last("if[18/6,bits,out]")+last("if[18/7,bits,out]")+last("if[21/8,bits,out]")+last("if[6/1,bits,out]")+last("if[2/4,bits,out]")+last("if[23/6,bits,out]")+last("if[22/8,bits,out]")+last("if[1/1,bits,out]")+last("if[1/2,bits,out]")+last("if[9/1,bits,out]")+last("if[3/2,bits,out]")+last("if[4/4,bits,out]")+last("if[4/2,bits,out]")+last("if[5/1,bits,out]")+last("if[5/4,bits,out]")+last("if[6/2,bits,out]")+last("if[6/3,bits,out]")+last("if[7/3,bits,out]")+last("if[8/4,bits,out]")+last("if[21/2,bits,out]")+last("if[21/4,bits,out]")+last("if[21/7,bits,out]")+last("if[20/8,bits,out]")+last("if[22/2,bits,out]")+last("if[22/4,bits,out]")+last("if[24/1,bits,out]")+last("if[22/6,bits,out]")+last("if[17/8,bits,out]")+last("if[19/5,bits,out]")+last("if[18/4,bits,out]")+last("if[19/4,bits,out]")+last("if[19/7,bits,out]")+last("if[20/2,bits,out]")+last("if[6/4,bits,out]")+last("if[24/4,bits,out]")+last("if[20/3,bits,out]")+last("if[20/4,bits,out]")+last("if[23/3,bits,out]")+last("if[23/5,bits,out]")+last("if[7/4,bits,out]")+last("if[18/1,bits,out]")+last("if[5/3,bits,out]")+last("if[4/1,bits,out]")
Characters: 2024

+last("if[7/1,bits,in]")+last("if[22/7,bits,in]")+last("if[2/1,bits,in]")+last("if[19/2,bits,in]")+last("if[7/2,bits,in]")+last("if[3/1,bits,in]")+last("if[3/3,bits,in]")+last("if[19/3,bits,in]")+last("if[8/3,bits,in]")+last("if[1/4,bits,in]")+last("if[8/1,bits,in]")+last("if[3/4,bits,in]")+last("if[8/2,bits,in]")+last("if[2/2,bits,in]")+last("if[24/5,bits,in]")+last("if[21/3,bits,in]")+last("if[24/2,bits,in]")+last("if[19/6,bits,in]")+last("if[22/3,bits,in]")+last("if[5/2,bits,in]")+last("if[17/1,bits,in]")+last("if[17/2,bits,in]")+last("if[17/4,bits,in]")+last("if[17/7,bits,in]")+last("if[20/6,bits,in]")+last("if[17/5,bits,in]")+last("if[21/1,bits,in]")+last("if[22/5,bits,in]")+last("if[17/6,bits,in]")+last("if[19/1,bits,in]")+last("if[17/3,bits,in]")+last("if[20/1,bits,in]")+last("if[18/5,bits,in]")+last("if[23/8,bits,in]")+last("if[18/8,bits,in]")+last("if[24/6,bits,in]")+last("if[18/6,bits,in]")+last("if[18/7,bits,in]")+last("if[21/8,bits,in]")+last("if[6/1,bits,in]")+last("if[2/4,bits,in]")+last("if[23/6,bits,in]")+last("if[22/8,bits,in]")+last("if[1/1,bits,in]")+last("if[1/2,bits,in]")+last("if[9/1,bits,in]")+last("if[3/2,bits,in]")+last("if[4/4,bits,in]")+last("if[4/2,bits,in]")+last("if[5/1,bits,in]")+last("if[5/4,bits,in]")+last("if[6/2,bits,in]")+last("if[6/3,bits,in]")+last("if[7/3,bits,in]")+last("if[8/4,bits,in]")+last("if[21/2,bits,in]")+last("if[21/4,bits,in]")+last("if[21/7,bits,in]")+last("if[20/8,bits,in]")+last("if[22/2,bits,in]")+last("if[22/4,bits,in]")+last("if[24/1,bits,in]")+last("if[22/6,bits,in]")+last("if[17/8,bits,in]")+last("if[19/5,bits,in]")+last("if[18/4,bits,in]")+last("if[19/4,bits,in]")+last("if[19/7,bits,in]")+last("if[20/2,bits,in]")+last("if[6/4,bits,in]")+last("if[24/4,bits,in]")+last("if[20/3,bits,in]")+last("if[20/4,bits,in]")+last("if[23/3,bits,in]")+last("if[23/5,bits,in]")+last("if[7/4,bits,in]")+last("if[18/1,bits,in]")+last("if[5/3,bits,in]")+last("if[4/1,bits,in]")+last("if[24/7,bits,in]")+last("if[18/2,bits,in]")+last("if[24/8,bits,in]")+last("if[23/7,bits,in]")
Characters: 2045