研读GATK最佳实践的研究者可能被以下描述所吸引：

Prior to GATK4 this was done through hierarchical merges with a tool called CombineGVCFs. This tool is included in GATK4 for legacy purposes, but performance is far superior when using GenomicsDBImport, which produces a datastore instead of a GVCF file.

即，gatk4的新的合并vcf功能非常好。于是跃跃欲试，

但是

该功能适合于数千级别的样品数量，少量样品还是应该使用此前的CombineGVCFs

GenomicsDBImport is used for samples in the order of thousands. For <1000 samples it is better to use CombineGVCFs.