Home > Article > Backend Development > How can I effectively manage memory usage and prevent garbage creation when working with pointers and garbage collection in Go?
In Python, Ruby, and JavaScript,pointers work differently than in Go. Go's garbage collector frees memory automatically, making it essential to understand pointer usage to optimize memory consumption and prevent unnecessary garbage creation.
Consider the fictitious API that returns a dataset of images with associated tags. We aim to create a data structure that maps each tag to a list of corresponding image URLs:
<code class="python">{ "ocean": [ "https://c8.staticflickr.com/4/3707/11603200203_87810ddb43_o.jpg" ], "water": [ "https://c8.staticflickr.com/4/3707/11603200203_87810ddb43_o.jpg", "https://c3.staticflickr.com/1/48/164626048_edeca27ed7_o.jpg" ], ... }</code>
One way to represent this mapping is to use pointers to the Image struct's URL field:
<code class="go">tagToUrlMap := make(map[string][]*string) for _, image := range result { for _, tag := range image.Tags { tagToUrlMap[tag.Name] = append(tagToUrlMap[tag.Name], &image.URL) } }</code>
Result:
An alternative approach is to use an intermediate variable and store a pointer to it:
<code class="go">tagToUrlMap := make(map[string][]*string) for _, image := range result { imageUrl = image.URL for _, tag := range image.Tags { tagToUrlMap[tag.Name] = append(tagToUrlMap[tag.Name], &imageUrl) } }</code>
Result:
Another option is to use a pointer to a string in the Image struct:
<code class="go">type Image struct { URL *string Description string Tags []*Tag }</code>
Considerations:
The optimal solution for memory efficiency is to use string interning, which ensures only one instance of a unique string value exists in memory.
<code class="go">var cache = map[string]string{} func interned(s string) string { if s2, ok := cache[s]; ok { return s2 } cache[s] = s return s }</code>
Implementation:
<code class="go">tagToUrlMap := make(map[string][]string) for _, image := range result { imageURL := interned(image.URL) for _, tag := range image.Tags { tagName := interned(tag.Name) tagToUrlMap[tagName] = append(tagToUrlMap[tagName], imageURL) } }</code>
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