Add support of the command ZDIFF and ZDIFFSTORE #2011
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Currently, we need to iterate all keys in the database in different places like the cluster migration and kvrocks2redis, but don't have an iterator for this purpose. It's very error-prone to implement this in different places since Kvrocks may add a new column family in the future, and we must be careful to iterate all keys in all column families. This would be a burden for maintenance, So we want to implement an iterator for iterating keys.
```C++
DBIter iter(storage, read_option);
for (iter.Seek(); iter.Valid(); iter.Next()) {
if (iter.Type() == kRedisString || iter.Type() == kRedisJSON) {
// the string/json type didn't have subkeys
continue;
}
auto subkey_iter = iter.GetSubKeyIterator();
for (subkey_iter.Seek(); subkey_iter.Valid(); subkey_iter.Next()) {
// handle its subkey and value here
}
}
```
When using this iterator, it will iterate the metadata column family first and check its type, if it's not a string or JSON, then it will iterate the corresponding column family to get subkeys. That said, if we have a key foo with type hash, then the iterator will iterate foo and foo:field1, foo:field2, and so on.
This solution can bring those benefits:
- The codes look more intuitive
- Can reuse this iterator if we want to iterate keys only
This closes #1989
|
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Add support of the command ZDIFF and ZDIFFSTORE
ZDIFF
ZDIFFSTORE (WIP)