perf: improve buildData by preallocating array

[nigrosimone]

No description provided.

[krausest]

Hi Nigro, I'm not going to merge it as it doesn't have any measurable impact on the results (optimized is your version with id++ inlined and the preallocated array);

Neither create rows (1k and 10k) nor update rows were not faster. Those are the benchmarks which should be impacted most by the change.