Decimal value stored in MySql DB with floating point error

Bug description

Decimal value stored with floating point error in mysqldb. Using a DECIMAL(20,10) field type in mysql and inserting the value 607013.31, in fact 607013.3100000001 is inserted. Checked the mysql logs and the error is already in the INSERT statement generated by prisma

How to reproduce

git clone https://github.com/unimatrix27/prismaissue cd prismaissue docker-compose up

This demo repo is a minimal environemt to demonstrate only this bug. Using docker-compose it sets up a mysql server, creates the demotable and runs NODE with the demoapp to show the bug

Expected behavior

The decimal value should be stored without floating point issues

Prisma information

prisma version 2.20, introspected DB, simplistic demo environment with no other code

Environment & setup

• OS: Docker NODE:15
• Database: MySql 5.7 (also tested 8.0)
• Node.js 15
• Prisma version: 2.20

const { PrismaClient } = require('@prisma/client')
var prisma =  new PrismaClient({ log: ['query', 'info', 'warn'] })
    
var enterTestData = prisma.demotable.create({
  data: {demofield: 607013.31}
    }).then(r => {
        console.log(r.demofield)
        // this console.log results in 607013.3100000001
    }
)

model demotable {
  id        Int      @id @default(autoincrement()) @db.UnsignedInt
  demofield Decimal? @db.Decimal(20, 10)
}

#6284

[unimatrix27]

upgraded to 2.20 also in the test repo, same result

[pimeys]

This is still super confusing. We’re having a meeting about floatish values tomorrow, hopefully we make it simpler to use in the future.

You’re not the first one having trouble… 😃