BE Core Module — Review Guide

Allocator-Aware Containers

Types in be/src/core/custom_allocator.h exist to route owned memory through Doris allocation and tracking paths.

Checkpoints

• [ ] For BE-owned buffers or containers whose memory should be tracked, prefer DorisVector, DorisMap, DorisUniqueBufferPtr, and related allocator-aware wrappers instead of the corresponding standard library ownership types

COW Column Semantics

Vectorized columns (IColumn) use intrusive-reference-counted copy-on-write.

Checkpoints

• [ ] Exclusive ownership guaranteed before mutate() on hot paths? Shared ownership triggers deep copy
• [ ] assume_mutable_ref() used only when exclusive ownership is already guaranteed?
• [ ] After Block::mutate_columns(), columns put back with set_columns()?
• [ ] convert_to_full_column_if_const() materializes only ColumnConst; ordinary columns may return shared storage?

Type System and Serialization

Upgrade/Downgrade Compatibility

• [ ] Serialized block/datatype layout changes gated with be_exec_version where required?
• [ ] Old and new serialization branches updated together (byte-size, serialize, deserialize)?

Decimal and Type Metadata

• [ ] Decimal result types check precision growth limits, no accidental incompatible widening?
• [ ] DecimalV2 original_precision/original_scale set intentionally, not left as UINT32_MAX sentinel?
• [ ] TScalarType optional fields filled for DECIMAL, CHAR/VARCHAR, DATETIMEV2?
• [ ] Flattened TTypeDesc.types traversal correct for nested complex types?

Block Merge Nullable Trap

MutableBlock::merge_impl() assumes nullable promotion shape without dynamic checking in release builds.

• [ ] New block merge logic preserves nullable-promotion preconditions?