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These settings are available in system.settings and are autogenerated from source.

shrink_over_allocated_columns_min_waste_bytes

Minimum absolute amount of wasted (reserved but unused) memory in a column, in bytes, for it to be shrunk to fit on INSERT. See shrink_over_allocated_columns_min_waste_ratio. Prevents reallocating columns whose over-allocation is small, where the memory saving would not justify the cost.

shrink_over_allocated_columns_min_waste_ratio

On INSERT, over-allocated columns (whose reserved memory exceeds the used memory, e.g. due to power-of-two growth of variable-length columns) are shrunk to fit before the expensive materialization and part-writing stages, to reduce peak memory usage. A column is shrunk only when allocatedBytes() > byteSize() * shrink_over_allocated_columns_min_waste_ratio and the absolute waste is at least shrink_over_allocated_columns_min_waste_bytes. Possible values:
  • Float greater than 1.
  • Value less than or equal to 1 disables the shrinking (the default 1.0 keeps it disabled).
Last modified on August 18, 2026