v.20.4Improvement

Column Size Calculation Optimized for MergeTree Data Parts

Now columns size is calculated only once for MergeTree data parts. #9827 (alesapin)
Columns size calculation for MergeTree data parts is optimized to be performed only once.

Why it matters

To improve performance by avoiding repeated computation of columns size during processing of MergeTree data parts, reducing overhead and speeding up operations relying on this metric.

How to use it

This optimization is applied automatically for all MergeTree table engines; users do not need to change any configuration or usage pattern.