Go或Rust中的数组数组？

Question

I'm porting some old PHP script to Go in order to achieve better performance. However, the old PHP is full of multidimensional arrays. Some excerpt from the codebase:

while (($row = $stmt->fetch(PDO::FETCH_ASSOC)) !== false) {
    $someData[$row['column_a']][$row['column_b']] = $row;
}

// ... more queries and stuff

if (isset($moreData['id']) && isset($anotherData['id']) && $someData[$anotherData['id']][$moreData['id']]) {
    echo $someData[$anotherData['id']][$moreData['id']];
}

Awful, i know, but i can't change the logic. I made the whole script perform much better by compiling with phc, but moving to a procedural, statically-typed language seems like a better move. How can i replicate those data structures efficiently with Go or Rust? It needs to be fault-tolerant when it comes to checking indexes, there's a lot of issets all around the script to check if the identifiers exist in the data structures.

Answer 1

In Go, this would be represented as a map. The syntax is map[key]value. So for example to store a multidimensional map of [string, string] -> int it would be map[string]map[string]int. If you know your indices are integers and densely packed, then you'd want to use slices. Those are simpler and look like [][]type.

As for the checking for a key existing, use this syntax, where m is a map:

if val, ok := m[key1][key2]; ok {
    ///Do something with val
}

Remember that to add a key to a multidimensional map you'd have to make sure the inner map is allocated before adding to it.

if _, ok := m[key]; !ok {
    m[key] = make(map[string]int)
}
m[key1][key2] = value

Obviously you'd want to wrap this up in a type with methods or a few simple functions.