Is Appending Strings to Go Slices Really That Inefficient?

Efficient Appending to a Variable-Length Container of Strings in Go

The challenge arises when accumulating matches from multiple regexes on voluminous log files. The question poses concerns over the potential performance drawbacks of resizing slices for such scenarios.

Existing Solutions

The response proposes using slices despite their non-constant append complexity. It argues that as the slice grows, the average append cost remains O(1), due to the proportional nature of the capacity increase. Empirical evidence is provided to support this claim, demonstrating that appending millions of strings incurs minimal overhead.

Alternative Approaches

The question also considers alternative methods, such as using a doubly-linked list. However, benchmarks indicate that this approach is slower than appending to slices. The response highlights that appending to slices involves copying only the string headers, which are small in size.

Recommendations for Large Files

For processing massive log files, the response advises against buffering the entire output in memory. Instead, it recommends streaming results as a single function, preferably with a []byte rather than a string type to avoid unnecessary conversions.

Additional Considerations

If maintaining the match list in RAM becomes necessary, keeping references to parts of large strings or byte slices can hinder garbage collection of the entire source data. To mitigate this issue, copying matches is recommended to prevent memory retention of the entire log data.

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