The API method trigger.addDependencies does not check whether dependencies exist prior to adding them, and there is no unique constraint across trigger_depends.triggerid_up and trigger_depends.triggerid_down to prevent the addition.

We had poorly written code that was unconditionally adding a dependency over and over, e.g.

1. request:
   {
   "jsonrpc":"2.0",
   "method":"trigger.addDependencies",
   "params":[
   { "triggerid": "100100000065000", "dependsOnTriggerid": "100100000064000" }

   ,
   ],
   "auth":"038e1d7b1735c6a5436ee9eae095879e",
   "id":2
   }

The problem is, when we checked what this was doing, through the API, it looked like trigger.addDependencies was being very clever, and doing nothing if the dependency already existed:

1. request:
   {
   "jsonrpc":"2.0",
   "method":"trigger.get",
   "params":{
   "filter": { "description": ["Sample trigger 1"], }

   ,
   "include_dependencies": "refer"
   },
   "auth":"6f38cddc44cfbb6c1bd186f9a220b5a0",
   "id":2
   }

No matter how many times we added the same dependency with trigger.addDependencies, trigger.get would show us the dependency only once.

However, each call to trigger.addDependencies added another row to the trigger_depends table. By the time we noticed what was happening, we had over half a million rows in the trigger_depends table, the increasing every half an hour when our script was run from cron.

We have subsequently modified our code to "include_dependencies" in the trigger.get request, and only trigger.addDependencies if the dependencies we want are missing. This reduces the likelihood of duplicate rows in trigger_depends table considerably.

Possible solutions that occur to me include:

1) Make trigger.addDependencies() fail when it receives a request to add an already existing dependency.
2) Throw a unique constraint across trigger_depends.triggerid_up and trigger_depends.triggerid_down and just let the mysql exception explode upward.
3) Make trigger.addDependencies() silently ignore a request to add an already existing dependency. Perhaps log a warning.