Why Couchbase round numeric values in a json Document?

问题

Is there anyone who had noted that Couchbase changes the numerical value of a property, over a certain limit, when recording a Json document?

Here is an example. For this test, I use the live input via the couchbase web interface.

The property "inputValue" corresponds to the value entered in the property "valueAfterSave" before clicking the save button.

The property "valueAfterSave" corresponds to the value after the save.

To a number with 16 digits, it's good:

{
  "inputValue": "1234567890123456",
  "valueAfterSave": 1234567890123456
}

But from 17 digits, the system begins to change the value:

{
  "inputValue": "12345678901234567",
  "valueAfterSave": 12345678901234568
}

{
  "inputValue": "12345678901234599",
  "valueAfterSave": 12345678901234600
}

{
  "inputValue": "12345678901234567890",
  "valueAfterSave": 12345678901234567000
}

Just out of curiosity with 40 digits

{
  "inputValue": "1234567890123456789012345678901234567890",
  "valueAfterSave": 1.234567890123457e+39
}

This behavior is specified somewhere? Is there a way to change it ?. There is the solution through String values but I admit that I'm curious.

I use Couchbase Server 2.1.0 on Windows 7 Pro 32-bit platform.

回答1:

Tugdual Grall, technical evangelist at Couhbase, brought me the answer.

This is due to the behavior of JavaScript when displaying such values as evidenced by the following test with NodeJS:

$ node
> console.log(12345678901234567890)
12345678901234567000

On the other hand, the value returned by the Java API is correct (12345678901234567890 in our example). It is just the console which shows this difference. If you modify the document, through the web administration console, it is the modified value which will be saved.

So be careful with the use of the administration Console when we handle this type of data.

Tug thank you.

来源：https://stackoverflow.com/questions/18532186/why-couchbase-round-numeric-values-in-a-json-document

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couchbase