# Join behaviour: count v. use parts v. msg.complete

**URL:** <https://discourse.nodered.org/t/join-behaviour-count-v-use-parts-v-msg-complete/98573>\
**Category:** Core Development\
**Tags:** join\
**Created:** [8 August 2025 09:57 UTC](https://discourse.nodered.org/t/join-behaviour-count-v-use-parts-v-msg-complete/98573 "2025-08-08T09:57:42Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![gregorius](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/gregorius/32/73816_2.png) [@gregorius](https://discourse.nodered.org/u/gregorius)\
**Post date:** [8 August 2025 09:57 UTC](https://discourse.nodered.org/t/join-behaviour-count-v-use-parts-v-msg-complete/98573/1 "2025-08-08T09:57:42Z")

</div>

Hi There,

I have the following test flows:

```flows
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messaage 5","property":"parts.index","propertyType":"msg","rules":[{"t":"eq","v":"5","vt":"num"},{"t":"else"}],"checkall":"false","repair":false,"outputs":2,"x":684,"y":1306,"wires":[["84f16f3a3289e391"],["b9443c4c6c253838"]]},{"id":"84f16f3a3289e391","type":"change","z":"24f35eaa8656755f","g":"179e4fcf622e01c3","name":"","rules":[{"t":"set","p":"complete","pt":"msg","to":"true","tot":"bool"},{"t":"delete","p":"parts","pt":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":980,"y":1301,"wires":[["95a5f1c8b0dec7b6"]]},{"id":"95a5f1c8b0dec7b6","type":"delay","z":"24f35eaa8656755f","g":"179e4fcf622e01c3","name":"","pauseType":"delay","timeout":"300","timeoutUnits":"milliseconds","rate":"1","nbRateUnits":"1","rateUnits":"second","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":false,"allowrate":false,"outputs":1,"x":1075,"y":1390,"wires":[["b9443c4c6c253838"]]},{"id":"c3163e2025e52553","type":"switch","z":"24f35eaa8656755f","g":"179e4fcf622e01c3","name":"payload 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messaage 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size == 6","property":"$count($$.payload)","propertyType":"jsonata","rules":[{"t":"eq","v":"6","vt":"num"}],"checkall":"false","repair":false,"outputs":1,"x":1396,"y":1809,"wires":[["8db21a56aa1c9a1c"]]},{"id":"8db21a56aa1c9a1c","type":"ut-assert-success","z":"24f35eaa8656755f","g":"3bcaaba6da95e125","name":"","x":1638,"y":1704,"wires":[]},{"id":"fdf58ceaaf3d5092","type":"group","z":"24f35eaa8656755f","name":"complete with count: delete parts only one message is passed 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messaage 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size == 6","property":"$count($$.payload)","propertyType":"jsonata","rules":[{"t":"eq","v":"6","vt":"num"}],"checkall":"false","repair":false,"outputs":1,"x":1405.9999694824219,"y":2179.66650390625,"wires":[["fd78ac57a80dc9c1"]]},{"id":"fd78ac57a80dc9c1","type":"ut-assert-success","z":"24f35eaa8656755f","g":"fdf58ceaaf3d5092","name":"","x":1633.9999694824219,"y":2084.66650390625,"wires":[]},{"id":"dfe78e0496467638","type":"debug","z":"24f35eaa8656755f","g":"fdf58ceaaf3d5092","name":"debug 447","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":true,"statusVal":"","statusType":"auto","x":1578.333251953125,"y":2260,"wires":[]},{"id":"c691ad76c434a610","type":"group","z":"24f35eaa8656755f","name":"complete with count: delete index and count, keep id and all 6 messages are passed 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messaage 5","property":"parts.index","propertyType":"msg","rules":[{"t":"eq","v":"5","vt":"num"},{"t":"else"}],"checkall":"false","repair":false,"outputs":2,"x":699.9999694824219,"y":2417.66650390625,"wires":[["ddc6b5d197073384"],["44cb831e1a92a75c"]]},{"id":"ddc6b5d197073384","type":"change","z":"24f35eaa8656755f","g":"c691ad76c434a610","name":"","rules":[{"t":"set","p":"complete","pt":"msg","to":"true","tot":"bool"},{"t":"delete","p":"parts.index","pt":"msg"},{"t":"delete","p":"parts.count","pt":"msg"},{"t":"set","p":"payload","pt":"msg","to":"fubar","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":995.9999694824219,"y":2412.66650390625,"wires":[["c8ec01bbbb8fd49a"]]},{"id":"c8ec01bbbb8fd49a","type":"delay","z":"24f35eaa8656755f","g":"c691ad76c434a610","name":"","pauseType":"delay","timeout":"300","timeoutUnits":"milliseconds","rate":"1","nbRateUnits":"1","rateUnits":"second","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":false,"allowrate":false,"outputs":1,"x":1068.9999694824219,"y":2529.66650390625,"wires":[["44cb831e1a92a75c"]]},{"id":"5b4df3e441a982fb","type":"switch","z":"24f35eaa8656755f","g":"c691ad76c434a610","name":"payload size == 6","property":"$count($$.payload)","propertyType":"jsonata","rules":[{"t":"eq","v":"6","vt":"num"}],"checkall":"false","repair":false,"outputs":1,"x":1404.9999694824219,"y":2570.66650390625,"wires":[["f85c866718ca6618"]]},{"id":"f85c866718ca6618","type":"ut-assert-success","z":"24f35eaa8656755f","g":"c691ad76c434a610","name":"","x":1646.9999694824219,"y":2465.66650390625,"wires":[]}]

```

They are four tests of the join node `manual` behaviour. All four tests have "use existing parts" activated and six separate messages are generated. Tests are:

- 
  1. drop the last message and send a `msg.complete = true` without the `msg.parts` and no count value on the join is set --\> only one message is passed out

- 
  1. drop the last message but send a `complete = true` with the parts attribute intact --\> six messages are passed out

- 
  1. count is set on join and parts is deleted and complete is true --\> six messages are passed out

- 
  1. count is set on join and parts is intact and complete is true --\> six messages are passed out

My question is that test 1 and test 3 should - in my opinion - both send only one message out. But because the count is set, test 3 sends all six messages - why?

In test 1 only a single message is sent because the `msg.parts` attribute has been delete from the message with the complete = true sent. So the completed message has no association to existing messages that have been collected using the parts attribute. Hence only the completed message is passed out.

In test 3 this is exactly the same: there is no association between the complete message and the message already collected _yet_ all messages are sent out once the complete is received. Seemingly only because the join node has a count value - which is higher than 6. Isn't this inconsistent?

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [7 October 2025 09:57 UTC](https://discourse.nodered.org/t/join-behaviour-count-v-use-parts-v-msg-complete/98573/2 "2025-10-07T09:57:50Z")

</div>

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