On 2nd of September, Teodor Sigaev committed patch:
Allow usage of huge maintenance_work_mem for GIN build. Currently, in-memory posting list during GIN build process is limited 1GB because of using repalloc. The patch replaces call of repalloc to repalloc_huge. It increases limit of posting list from 180 millions (1GB / sizeof(ItemPointerData)) to 4 billions limited by maxcount/count fields in GinEntryAccumulator and subsequent calls. Check added. Also, fix accounting of allocatedMemory during build to prevent integer overflow with maintenance_work_mem > 4GB. Robert Abraham <firstname.lastname@example.org> with additions by me
Continue reading Waiting for 9.6 – Allow usage of huge maintenance_work_mem for GIN build.