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75 lines
2.2 KiB
Markdown
75 lines
2.2 KiB
Markdown
# go-structr
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A performant struct caching library with automated indexing by arbitrary combinations of fields, including support for negative results (errors!). An example use case is in database lookups.
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Some example code of how you can use `go-structr` in your application:
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```golang
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type Cached struct {
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Username string
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Domain string
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URL string
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CountryCode int
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}
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var c structr.Cache[*Cached]
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c.Init(structr.Config[*Cached]{
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// Fields this cached struct type
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// will be indexed and stored under.
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Indices: []structr.IndexConfig{
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{Fields: "Username,Domain", AllowZero: true},
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{Fields: "URL"},
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{Fields: "CountryCode", Multiple: true},
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},
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// Maximum LRU cache size before
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// new entries cause evictions.
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MaxSize: 1000,
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// User provided value copy function to
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// reduce need for reflection + ensure
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// concurrency safety for returned values.
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CopyValue: func(c *Cached) *Cached {
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c2 := new(Cached)
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*c2 = *c
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return c2
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},
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// User defined invalidation hook.
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Invalidate: func(c *Cached) {
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log.Println("invalidated:", c)
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},
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})
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var url string
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// Load value from cache, with callback function to hydrate
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// cache if value cannot be found under index name with key.
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// Negative (error) results are also cached, with user definable
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// errors to ignore from caching (e.g. context deadline errs).
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value, err := c.LoadOne("URL", func() (*Cached, error) {
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return dbType.SelectByURL(url)
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}, url)
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if err != nil {
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return nil, err
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}
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// Store value in cache, only if provided callback
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// function returns without error. Passes value through
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// invalidation hook regardless of error return value.
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//
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// On success value will be automatically added to and
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// accessible under all initially configured indices.
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if err := c.Store(value, func() error {
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return dbType.Insert(value)
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}); err != nil {
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return nil, err
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}
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// Invalidate all cached results stored under
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// provided index name with give field value(s).
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c.Invalidate("CountryCode", 42)
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```
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This is a core underpinning of [GoToSocial](https://github.com/superseriousbusiness/gotosocial)'s performance. |