takeUntil() after a filter() behaves differently from take(n) in pipe

this.activatedRoute.queryParamMap
.pipe(
// activatedRoute.queryParamMap emits null values first. So let's avoid it
filter((paramMap) => paramMap && paramMap.keys.length > 0),
// unsubscribe immediately if some params are found
take(1),
// If the params are really empty, filter will never pass. So let's unsubscribe after sometime
takeUntil(timer(1000)),
delay(1),
combineLatestWith(this.sortableColumns$),
)
.subscribe(([paramMap, sortableColumns]) => {
console.log("paramMap")
this.setTableOptionsFromUrl(paramMap, sortableColumns);
});


I have the above code.

• So take(1) unsubscribes from the source observable only when the filter passes after a valid emission from source (only when there is atleast one paramMap)
• takeUntil also comes after the filter but it unsubscribes from the source irrespective of whether the filter passes or not once the timer emits

My question is,

• If filter blocks the pipeline until it passes shouldn't it block takeUntil too?
• If this is the expected behaviour, how can I know which operators will be blocked by the filter operator and which all will not be
• If this is not the expected behaviour, how else can we achieve this?

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