fix: Refresh Map Vector pointers after reallocation #15338
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…r#15338) Summary: Fix stale pointer issue in MapWriter causing segfault in FB_DECOMPRESS_BERINGEI_TIME_BLOCK UDF. When a UDF calls `add_item()` repeatedly on a Map result writer, the underlying vector may reallocate to a larger memory location when full. However, MapWriter retains pointers to the old memory location, causing subsequent writes to access freed memory and segfault. Fix involves refreshing - valuesVector_ = new vector location - data_ = new memory pointer So next add_item() adds to correct location. -- Seg Fault in FB_DECOMPRESS_BERINGEI_TIME_BLOCK example - for (const auto& [timestamp, value] : timeValues) { int64_t timestampMs = timestamp * 1000; // Convert to milliseconds auto [keyWriter, valueWriter] = result.add_item(); keyWriter = Timestamp::fromMillis(timestampMs); valueWriter = value; <<<< HERE } emplace() won't help in the UDF, as it internally calls add_item(). Both face this same issue. Differential Revision: D85692836
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Summary:
Fix stale pointer issue in MapWriter causing segfault in FB-internal UDF.
When a UDF calls add_item() repeatedly on a Map result writer, the underlying vector may reallocate to a larger memory location when full. However, MapWriter retains pointers to the old memory location, causing subsequent writes to access freed memory and segfault.
Fix involves refreshing
valuesVector_ = new vector location
data_ = new memory pointer
So next add_item() adds to correct location.
Differential Revision: D85692836