Go Deep Copy: When Does `gob` Outperform `json`?

Performance Comparison of Object Deep-copying Methods in Go: JSON vs gob

Background

In Go, efficient object deep-copying is crucial for data manipulation and transferring. Two popular methods are encoding/gob and encoding/json. While common wisdom suggests gob should outperform json, some users have encountered unexpected results. This article investigates this anomaly and explores alternative deep-copying approaches.

gob vs json Performance Difference

The performance advantage of gob stems from its custom codec compilation for each data type. However, this process incurs a cost when handling the first value of a given type, as it requires transmitting type definitions along with the data.

Our test with an array type multiplication demonstrates this effect. In the original version, json outperformed gob due to its lack of type-transmission overhead. However, in the modified version with larger arrays, gob became faster as the cost of transmitting type info was amortized over more values.

Testing Methodology

Measuring performance by comparing microsecond execution times as in the provided test code can yield inaccurate results. Go provides built-in testing and benchmark tools that offer more reliable and precise measurements.

Caveats of Reflection-Based Cloning

Both gob and json utilize reflection for cloning, which has limitations:

• It only clones exported fields.
• It often doesn't preserve pointer equality.
• It cannot handle self-referencing structures effectively.

The Proper Cloning Method

The most efficient and reliable method for deep-copying involves creating custom copying logic within the type's package. This ensures accurate field duplication, preserves pointer equality, and accommodates self-referencing structures. While not as convenient, it outperforms generic reflection-based approaches and minimizes memory usage.

The above is the detailed content of Go Deep Copy: When Does `gob` Outperform `json`?. For more information, please follow other related articles on the PHP Chinese website!