Data types for MongoDB

Writing a LUA module recently MongoDB version 3.2,lua is 5.3.1. The underlying is written in C + +, and the function is exposed to the LUA call. But when you print the results in Lua, something strange happens. First, the contents of the database:

> Db.item.Find(){ "_id":2001,"Amount":999 }{ "_id":2002,"Amount": +,"name":"Kfsjadlfasfkljeihfdsfkasfjslkfjei"}

Of course, this is what I write to test, it doesn't make sense. However, printing in Lua is like this:

Table0xff0ae0{    "1"= table:0xfe4800    {        "name"="Kfsjadlfasfkljeihfdsfkasfjslkfjei"        "_id"=2002.0        "Amount"=78.0    }    "0"= table:0xfe4610    {        "Amount"=999.0        "_id"=2001.0    }}

The data is correct, the problem is: Like 2001 of these shaping numbers for everything has a decimal point. With a little trace of the code, you can see that the data from MongoDB find is already double, so lua_pushnumber instead of Lua_pushinteger when you return to the LUA layer. Causes Lua to think of the number as not an integer. This is how the decimal point comes in.

However, MongoDB data is based on Bson, while Bson is of type int. Then, the data is entered in the MongoDB type is already double. And the data I entered in the MONGO shell, the problem has to be traced from the MONGO shell.

As mentioned in the official website https://docs.mongodb.org/v3.0/core/shell-types/, the MONGO shell is of a type. However, when we enter it, we usually enter it in this way:

Db.item.insert ({_id:2002, Amount:)

No type is specified, and the JSON format is used. The problem is: The JSON format has only number type, and does not subdivide numbers such as int, double, so for the sake of insurance, it is obvious that the MONGO shell all save it as a double type. It was clear that the authorities had long noticed the problem, allowing the type to be specified when entering data in the shell, such as:

Db.item.insert ({_id:numberint), amount: +,name:"  Kfsjadlfasfkljeihfdsfkasfjslkfjei"})

Use a function such as numberint to specify the type. Once specified, this is the current query in Lua, with the result:

Table0xff0ae0{    "2"= table:0xfe5cd0    {        "name"="Kfsjadlfasfkljeihfdsfkasfjslkfjei"        "_id"= the        "Amount"=78.0    }    "1"= table:0xfe4800    {        "name"="Kfsjadlfasfkljeihfdsfkasfjslkfjei"        "_id"=2002.0        "Amount"=78.0    }    "0"= table:0xfe4610    {        "Amount"=999.0        "_id"=2001.0    }}

Discovery Data 2009 is displayed as normal. Later, when the program is running, the data is entered from the program, which is not a problem.

Data types for MongoDB