On 8 December 2012 14:41, Andres Freund <and...@2ndquadrant.com> wrote: > Is anybody planning to work on this? There hasn't been any activity > since the beginning of the CF and it doesn't look like there is much > work left?
I took another look at this. The growmemtuples bool from Jeff's original patch has been re-added. My strategy for preventing overflow is to use a uint64, and to use Min()/Max() as appropriate. As Robert mentioned, even a 64-bit integer could overflow here, and I account for that. Actually, right now this is only a theoretical problem on 64-bit platforms, because of the MaxAllocSize limitation - allowedMem being more than 2^38 (bytes, or 256GB) is a situation in which we won't repalloc anyway, because of this: /* * On a 64-bit machine, allowedMem could be high enough to get us into * trouble with MaxAllocSize, too. */ ! if ((Size) (newmemtupsize) >= MaxAllocSize / sizeof(SortTuple)) ! goto noalloc; I reintroduced this check, absent in prior revisions, positioned around the new code: ! /* We assume here that the memory chunk overhead associated with the ! * memtuples array is constant and so there will be no unexpected addition ! * to what we ask for. (The minimum array size established in ! * tuplesort_begin_common is large enough to force palloc to treat it as a ! * separate chunk, so this assumption should be good. But let's check it, ! * since the above fall-back may be used.) */ if (state->availMem <= (long) (state->memtupsize * sizeof(SortTuple))) return false; Though we use a uint64 for memtupsize here, we still don't fully trust the final value: ! newmemtupsize = Min(Max(memtupsize * allowedMem / memNowUsed, ! memtupsize), ! memtupsize * 2); I also added a brief note within tuplestore.c to the effect that the two buffer sizing strategies are not in sync. Thoughts? -- Peter Geoghegan http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training and Services
sortmem_grow-v5.patch
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