Fix merge key order, clear anchors after resolving #807

Job	Run time
samples (Debug, ubuntu-20.04)	2m 36s
samples (Release, ubuntu-20.04)	3m 7s
samples (Debug, windows-2019)	3m 18s
samples (Release, windows-2019)	9m 29s
samples (Debug, macos-latest)	1m 42s
samples (Release, macos-latest)	2m 4s
	22m 16s

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