I would like to ask what consideration is the immutableOpenmap in Elasticsearch designed for? What kind of utility does it have? It is used in both aliasmetadata and indexmetadata. My personal guess is that it has something to do with atomicity, but I don't get the full understanding from the code.
From the source
An immutable map implementation based on open hash map.
Immutable simply means that once you create it, you cannot modify its content anymore. All methods that would mutate the content, whether keys or values, will throw UnsupportedOperationException.
I need to use redis in golang as cache and store a array of structs in it. Since redis allows only storing array of strings(correct me if I'm wrong), I'll marshal the items in my array. Was wondering shall I use redis list where I'm storing marshaled structs in string format OR I can just marshal the whole array and store as key<>value in redis and not use list. One pro of using list is I can fetch ranged items from the list but scale is not the problem here since I'll be storing less than 100 items in the list. What else should I consider here.
Thankyou!!
The answer depends of how you want to use redis
For instance, store one struct using json (or any kind of serialization) and store it in a single position is easy to read / write.
But if you need to efficiently retrieve/ update one field, you can save it in a different way. However this scenario is pretty rare and complex to handle.
For instance you need to be sure you write always in the same order, to calculate the right offset. If you need to add a new field, will be really difficult to be 100% backward compatible. You probably need to create a new type (like a version 2).
I want to parse a huge json with more accuracy and less code implementation. Is there any possibility to implement.i am able to parse a huge file into the buffer but when I try to access values of json I need to do individually for all the keys and values. Will there any possibility to retrieve values of objects only when needed. Please provide my example for parsing huge json file and using values
I have a std::map<CString,CString> which I subsequently iterate after it is populated.
Is it possible to sort this map by the key value? The key is a name. So when I iterate the map I would like the names in A-Z order.
std::map is standard C++ specific container which already keeps the data sorted based on key. So no need to sort after it has been populated. But yes, in order to better handle the cases of duplicate keys, you should use std::multimap since name can be duplicated if used as key.
Also, it will be better if you use CMap Class, since mixing standard C++ and windows classes seems bit clumsy.
I keep running into a certain kind of data structure, and wonder if there is a name for it. It maps very closely to JSON, but not exactly. The rules are:
It is composed entirely of maps, arrays, and primitives.
It is hierarchical. Maps contain name/value pairs, where a value can
be another map, an array, or a primitive. Arrays contain values with the same rules.
The top level is always a map.
The primitives are strings, integers, floats, booleans, and possibly
dates.
Sometimes the map is just an unordered hash, and sometimes the order
of the name/value pairs matter.
This is a really, really useful structure. You can use it to represent documents, database records, various messages, http requests, lots of stuff. I've run into it in Freemarker (as the 'data model'), Mongo, and anything that uses JSON.
It's not really JSON, because that's a file format, not a specification for a particular data structure. It's not an "object", because object trees can point to other things, like streams and functions. It's not a DOM.
What is it?
Around the office, we've started to call it a "garg", for "generalized argument".
It's not really JSON, because that's a file format, not a specification for a particular data structure.
It might not be JSON (since the specs include syntax rules), but your structure definition defines the same data structure as JSON does.
I don't think it's useful to name this structure. When you are talking about data, just call it data. When you need to interchange data you need a data-interchange format. Now JSON proves to be one damn good one.
JSON isn't just a file format. JSON is also a data structure.
From JSON.org
JSON is built on two structures:
A collection of name/value pairs. In various languages, this is
realized as an object, record, struct, dictionary, hash table, keyed
list, or associative array.
An ordered list of values. In most
languages, this is realized as an array, vector, list, or sequence.
These are universal data structures.
It is a generic data storage structure that carries around hierarchical data. I don't have a generic name for it, but if I were to implement such a beast in, say, C++, I'd probably call the abstract base class a Variant, and name the concrete types by their names: Integer, Array, Map, etc. I'd chuck them in a namespace that would relate to where I'd use them - or maybe I'd prefix the types themselves. I've seen such structures used as well, but I don't know if there is a name that I'd recognize. A DataStore, Environment, StorageBin, or anything that is generic and implies storage of data would do.
I don't see myself calling such a class hierarchy JSON, though. I would provide a JsonSerializer or some such to map this data to JSON, if I needed it.
It sounds like you're describing an associative array, with optional ordering.
That's what JSON represents, except that (I believe) JSON doesn't impose an ordering requirement. Naturally, many other representations also describe associative arrays, which is why JSON is a popular text serialization.
Update 1: JSON isn't properly an associative array. It is a description of object properties. Because it is very often construed as an associative array, many people make the same mistake I did. In fact, "object notation" is the proper name for it - surprise, surprise. :) In addition, JSON isn't a file format - it's a text serialization or markup language, which is different from a file format.
The structure is a tree with different kinds of values stored at its leafs.
In Boost, a similar structure is called Property Tree.