On 2026-Mar-25, Antonin Houska wrote: > I've taken a look, but not sure if the tuple slots help here. In > heapam_relation_copy_for_cluster(), both table_scan_getnextslot() and > index_getnext_slot() call ExecStoreBufferHeapTuple() -> > tts_buffer_heap_store_tuple(), which AFAICS do not deform the tuple. > Then ExecFetchSlotHeapTuple() is used to retrieve the tuple, but > again, the underlying slot (TTSOpsBufferHeapTuple) handles it by > copying rather than deforming / forming. Thus I think the explicit > "reforming" currently does not add any performance overhead.
Looking again, I think we should leave this alone for now. The existing code (looking at heapam_relation_copy_for_cluster) is somewhat silly, in that we do a bunch of operations with slots, then we heap-ify the tuple by doing ExecFetchSlotHeapTuple(), then we do the reform_and_rewrite dance, which must deform the tuple only to immediately form it back; and after we've done that, we make it go through the rewriteheap.c motions, which again deforms and forms back (in certain cases). This code structure seems mostly a relic from the time when heapam.c was all we had, and I think we should rewrite it from scratch to work using only slots. But not for this patch, and not for pg19, because I think that's going to take some nontrivial effort on its own. So for REPACK in pg19 I think we should just do the simplest thing possible, and do the minimum amount of deform/form dance necessary to make this whole thing work. I suppose that that's what the submitted code (v44-0008) does, so I'm going to leave it at that. -- Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/ "In Europe they call me Niklaus Wirth; in the US they call me Nickel's worth. That's because in Europe they call me by name, and in the US by value!"
