7. The method of claim 1 , further comprising: when a flush condition is satisfied, performing a flush operation, including building a sorted map, the sorted map relating globally unique identifiers to document identifiers assigned to documents since a prior flush operation.
7. The method of claim 1 , further comprising: when a flush condition is satisfied, performing a flush operation, including building a sorted map, the sorted map relating globally unique identifiers to document identifiers assigned to documents since a prior flush operation. 8. The method of claim 7 , further comprising: when a merge condition is satisfied, performing a merge operation, the merge operation including merging a layered plurality of sorted maps produced by previous flushing operations, the merge operation further including producing a merged map relating globally unique identifiers to document identifiers assigned to documents.