While reading nodeAgg.c, I noticed code that uses CHUNKHDRSZ to help figure out how much memory a tuple uses so the code knows when to spill to disk. CHUNKHDRSZ is currently set to 16 bytes, which was fine when that code was added, but it's a few years out-of-date since c6e0fe1f2 in 2022.
The attached adjusts the 16 to sizeof(MemoryChunk), which is normally 8, but 16 in assert builds. The memory accounting should be more accurate with the patch, however, that accounting doesn't account for blocks that the chunks are on. For that reason, I'm thinking of not backpatching this as it will make hash aggregates use a bit more memory than unpatched before spilling, albeit, for most cases, closer to the hash_mem limit, which is when the spilling should be happening. Sound ok? David
fix_nodeAgg_CHUNKHDRSZ.patch
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