How to delete exact matched data from nested map in golang

Question

I am using IM cache with nested map data structure(map[string]map[string]map[string]string-map[ip]map[port]map[path]string) in the golang project, for one ip there is a multiple combination of port, path values can be added to the map, here is the concern, I have to delete the exact combination of ip,port,path from the above nested map values. Below I am attaching the code. I am planning to delete http://10.3.5.6:8080/path7 from the map.

**package main

import "fmt"

type cacheData map[string]map[string]map[string]string

func main() {
    cacheEntries := make(cacheData)
    cacheEntries["http://10.3.5.6"] = make(map[string]map[string]string)
    cacheEntries["http://10.3.5.6"]["8080"] = make(map[string]string)
    cacheEntries["http://10.3.5.6"]["8080"]["/path7"] = "URL"
    cacheEntries["http://10.3.5.7"] = make(map[string]map[string]string)
    cacheEntries["http://10.3.5.7"]["8080"] = make(map[string]string)
    cacheEntries["http://10.3.5.7"]["8080"]["/path7"] = "URL"
    fmt.Println(cacheEntries)
    delVal := make(map[string]map[string]string)
    delVal["http://10.3.5.6"] = make(map[string]string)
    delVal["http://10.3.5.6"]["8080"] = "/path7"
    delete(cacheEntries, delVal)
    fmt.Println(cacheEntries)
}**

The above code is throwing compilation error saying ./prog.go:21:23: cannot use delVal (variable of type map[string]map[string]string) as type string in argument to delete , this is because delete function only expects string value for delete. Any suggestion to solve the above problem or any other approaches recommended to solve please let me know.

Thanks in advance.

VonC · Accepted Answer · 2022-10-17T11:36:04.857

First, since there is no entry "/path", I would assume you meant "/path7"

Second, to delete a key in a map, you simply need to reference the existing map, not to recreate it.

See playground

package main

import "fmt"

type cacheData map[string]map[string]map[string]string

func main() {
    cacheEntries := make(cacheData)
    cacheEntries["http://10.3.5.6"] = make(map[string]map[string]string)
    cacheEntries["http://10.3.5.6"]["8080"] = make(map[string]string)
    cacheEntries["http://10.3.5.6"]["8080"]["/path7"] = "URL"
    cacheEntries["http://10.3.5.7"] = make(map[string]map[string]string)
    cacheEntries["http://10.3.5.7"]["8080"] = make(map[string]string)
    cacheEntries["http://10.3.5.7"]["8080"]["/path7"] = "URL"
    fmt.Println(cacheEntries)
    delMap := cacheEntries["http://10.3.5.6"]["8080"]
    delVal := "/path7"
    delete(delMap, delVal)
    fmt.Println(cacheEntries)
}

Result:

map[http://10.3.5.6:map[8080:map[/path7:URL]] http://10.3.5.7:map[8080:map[/path7:URL]]]
map[http://10.3.5.6:map[8080:map[]] http://10.3.5.7:map[8080:map[/path7:URL]]]

For deleting an exact tuple (IP, port, path), see this example:

package main

import "fmt"

type cacheData map[string]map[string]map[string]string

func main() {
    cacheEntries := make(cacheData)
    cacheEntries["http://10.3.5.6"] = make(map[string]map[string]string)
    cacheEntries["http://10.3.5.6"]["8080"] = make(map[string]string)
    cacheEntries["http://10.3.5.6"]["8080"]["/path7"] = "URL"
    cacheEntries["http://10.3.5.7"] = make(map[string]map[string]string)
    cacheEntries["http://10.3.5.7"]["8080"] = make(map[string]string)
    cacheEntries["http://10.3.5.7"]["8080"]["/path7"] = "URL"
    fmt.Println(cacheEntries)
    del("http://10.3.5.6", "8080", "/path7", cacheEntries)
    fmt.Println(cacheEntries)
}

func del(ip, port, path string, cacheEntries cacheData) {
    mapIP := cacheEntries[ip]
    if mapIP == nil {
        return
    }
    mapPort := mapIP[port]
    if mapPort == nil {
        return
    }
    delete(mapPort, path)
    if len(mapPort) == 0 {
        delete(mapIP, port)
    }
    if len(mapIP) == 0 {
        delete(cacheEntries, ip)
    }
}

Result:

map[http://10.3.5.6:map[8080:map[/path7:URL]] http://10.3.5.7:map[8080:map[/path7:URL]]]
map[http://10.3.5.7:map[8080:map[/path7:URL]]]

Thanks #Vonc, but I have to delete the entire matched record from the nested map — madhusri mannuru, Oct 17 '22 at 10:10
@madhusrimannuru Do you mean delete everything under "http://10.3.5.6"? As in [this example](https://go.dev/play/p/NAMFcS8j-1t)? — VonC, Oct 17 '22 at 11:25
@madhusrimannuru I have edited the answer to address a tuple removal (IP, port, path). — VonC, Oct 17 '22 at 11:36

How to delete exact matched data from nested map in golang

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