arcpy.AddMessage() known limitation?

[SamyBouma_Ngock1]

No issue with my script as it is running fine but just for my information (or making sure my system is not giving up on me...),

is there a known limitation with arcpy.AddMessage not automatically updating the tool dialog box after ~65500 rows?

However, one can still see the vertical scrollbar update its position upward as new lines are 'added' to the console.

[JoshuaBixby · Accepted solution]

It probably isn't coincidence that you are running into issues ~65,500 messages and the maximum value of an unsigned short int is 65,535. 

I can't say for sure whether you are running into a buffer/queue limit, but it seems that way.  That said, that is a fairly excessive amount of messaging (I am differentiating messaging from logging).  Until you do sort out what is happening, maybe using a log file would work better since it seems you want to log millions of events.

[curtvprice]

Couldn't agree more with Joshua - GP messages are saved both in the current document and to the geoprocessing history by default -- kind of a bad idea to stuff many MB of text messages in both these places!

[ClintonDow1]

I agree with Joshua's comment that this limitation is due to the maximum short int value. 

I would recommend either implementing logging to a file instead of messaging to the GP pane as he suggests, using a progress bar, or doing some sort of batching on your messages (ie: only print every 1000 messages using a counter to determine progress)

[curtvprice]

Controlling the progress dialog box—Help | ArcGIS Desktop 

This help topic also has the stub code to do something every 1000 records if you want to go the messaging route.

[SamyBouma_Ngock1]

Well, thank you all for your feedback.

I understand that I'll have to observe some best practices for messaging and/or logging.

However, the issue I described is a reproducible one since for each run it happens at the same line number. I also noted that when clicking in the console window, line count information gets refreshed... I am not that concerned.