fix(core): Account for size change on json object defragment #6053
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abhijat
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Nov 13, 2025
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abhijat
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Dec 15, 2025
src/core/compact_object.cc
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| json_ptr = AllocateMR<JsonType>(DeepCopyJSON(old)); | ||
| DeleteMR<JsonType>(old); | ||
| if (const ssize_t delta = mr->used() - before; delta != 0) { | ||
| bytes_used += delta; |
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there is a helper function UpdateSize, maybe it should be used here. Mainly it protects against object size going down to negative. I'm not clear when that will happen though.
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I changed to use UpdateSize, it is more defensive.
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Signed-off-by: Abhijat Malviya <abhijat@dragonflydb.io>
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romange
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Dec 17, 2025
| if (did) { | ||
| reallocations++; | ||
| if (const ssize_t delta = it->second.MallocUsed() - original_size; | ||
| delta != 0 && db_table != nullptr) { |
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probably not but I added it to be defensive as we access a field via the pointer.
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i usually do not like these things as it raises questions where this state is possible. it's better to DCHECK to assert the precondition than have such ifs
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I see, I will remove it in a follow up
romange
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Dec 17, 2025
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For JSON type, after defragmentation used size may change. The change is propagated to the db stats object, so that metrics observe the change and reduction in memory usage (if any) correctly.
The JSON object records the change by observing the diff in bytes used by the memory resource, this is the same pattern used in
json_family.ccetc. Once the change is determined it is set in thebytes_usedfield for the json object.The delta update is in effect for all objects whose size changes, not just JSON type objects.