In Graph API, how to transform the outcome from a windowing function to non-grouped value

[revozhang]

I have the following graph

{
	node1: {
		type: 'operator',
		nodeType: 'window',
		props: {
			type: 'tumblingwindow',
			unit: 'ss',
			size: 10,
		},
	},
}, {
	node2: {
		type: 'operator',
		nodeType: 'aggfunc',
		props: {
			expr: 'avg(value)',
		},
	},
}, {
	node3: {
		type: 'operator',
		nodeType: 'function',
		props: {
			expr: 'abs(avg)',
		},
	},
},

but got error message saying:

collection type mismatch, expect non-grouped collection, got grouped collection

Can I use a pick operator to select the first element of the collection? Thanks.

[revozhang]

Update
I replaced node3 with a script node trying to process the avg value:

node3: {
                type: 'operator',
                nodeType: 'script',
                props: {
                  script:
                    'function exec(msg, meta) { return msg.avg}',
                  isAgg: true,
                },
              }

Now the error message says:

input type mismatch, expect row, got collection

[revozhang]

Hi, @ngjaying thank you for looking into this. Do you have a solution for this now or is it coming? I was trying to implement my own function plugin to covert the collection into a row, but it seems to be a circle. In order to consume the data from the window function, my function needs to declare IsAggregate() true. Thus my function becomes one that outputs collection again. Is there a way to get around this dilemma? Thanks!

[ngjaying]

Sorry, I don't have time to look into this deeply. I don't think we have the mechanism to convert collection back into one row now.

[revozhang]

OK. Do you have any tips how I should go ahead and implement it? As mentioned above, if I declare IsAggregate true for my function, does it mean my function only accept collection and only output collection too? Thanks!

[ngjaying]

OK. Do you have any tips how I should go ahead and implement it? As mentioned above, if I declare IsAggregate true for my function, does it mean my function only accept collection and only output collection too? Thanks!

Yes, this is the current design

[ghezzis]

Hello,
thank you for this amazing project.
I was wondering if there is any update about this topic.

Thanks

[ngjaying]

There is no update on this issue. Welcome to share your ideas here.

[ngjaying]

This should be supported after implementing #2504