func()

in kll/items_sketch.go [835:904]

• 58 lines of code
• 10 McCabe index (conditional complexity)

func (s *ItemsSketch[C]) compressWhileUpdatingSketch() {
	level := findLevelToCompact(s.k, s.m, s.numLevels, s.levels)
	if level == s.numLevels-1 {
		//The level to compact is the top level, thus we need to add a level.
		//Be aware that this operation grows the items array,
		//shifts the items data and the level boundaries of the data,
		//and grows the levels array and increments numLevels_.
		s.addEmptyTopLevelToCompletelyFullSketch()
	}
	myLevelsArr := s.levels
	rawBeg := myLevelsArr[level]
	rawEnd := myLevelsArr[level+1]
	// +2 is OK because we already added a new top level if necessary
	popAbove := myLevelsArr[level+2] - rawEnd
	rawPop := rawEnd - rawBeg
	oddPop := rawPop%2 == 1
	adjBeg := rawBeg
	if oddPop {
		adjBeg++
	}
	adjPop := rawPop
	if oddPop {
		adjPop--
	}
	halfAdjPop := adjPop / 2

	//the following is specific to generic Items
	myItemsArr := s.GetTotalItemsArray()
	if level == 0 { // level zero might not be sorted, so we must sort it if we wish to compact it
		tmpSlice := myItemsArr[adjBeg : adjBeg+adjPop]
		sort.Slice(tmpSlice, func(a, b int) bool {
			return s.compareFn(tmpSlice[a], tmpSlice[b])
		})
	}
	if popAbove == 0 {
		randomlyHalveUpItems(myItemsArr, adjBeg, adjPop, s.deterministicOffsetForTest)
	} else {
		randomlyHalveDownItems(myItemsArr, adjBeg, adjPop, s.deterministicOffsetForTest)
		mergeSortedItemsArrays(
			myItemsArr, adjBeg, halfAdjPop,
			myItemsArr, rawEnd, popAbove,
			myItemsArr, adjBeg+halfAdjPop, s.compareFn)
	}
	newIndex := myLevelsArr[level+1] - halfAdjPop // adjust boundaries of the level above
	s.levels[level+1] = newIndex

	if oddPop {
		s.levels[level] = myLevelsArr[level+1] - 1          // the current level now contains one item
		myItemsArr[myLevelsArr[level]] = myItemsArr[rawBeg] // namely this leftover guy
	} else {
		s.levels[level] = myLevelsArr[level+1] // the current level is now empty
	}

	if level > 0 {
		amount := rawBeg - myLevelsArr[0] // adjust boundary

		for i := amount; i > 0; i-- {
			// Start from the end as we are shifting to the right,
			// failing to do so will corrupt the items array.
			tgtInx := myLevelsArr[0] + halfAdjPop + i - 1
			stcInx := myLevelsArr[0] + i - 1
			myItemsArr[tgtInx] = myItemsArr[stcInx]
		}
	}
	for lvl := uint8(0); lvl < level; lvl++ {
		newIndex = myLevelsArr[lvl] + halfAdjPop //adjust boundary
		s.levels[lvl] = newIndex
	}
	s.items = myItemsArr
}