PreprocessTableMerge

PreprocessTableMerge is…​FIXME

PreprocessTableMerge is created when DeltaMergeBuilder is requested to execute

PreprocessTableMerge takes a single SQLConf to be created.

Creating MergeIntoCommand Instance — apply Method

apply(mergeInto: MergeInto): MergeIntoCommand

apply…​FIXME

apply is used when…​FIXME