Fixed empty blob

[YaroslavRepeta]

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Description of change

SELECT query returns null instead of empty Buffer for BLOB type

[codecov]

Codecov Report

Merging #9441 into master will increase coverage by <.01%.
The diff coverage is n/a.

[sushantdhiman]

I dont think this works, can you show me a failing case

[YaroslavRepeta]

I'm not sure where the right place to add test case for this.

What I did here is only removed if what causes returning null instead of empty buffer.

[sushantdhiman]

Ok show me example of what you are trying to solve, paste it here

[YaroslavRepeta]

Something like:

expect(
    (await model.findOne({ some_where_clause })).empty_buffer_column
).to.equal(Buffer.from(""));

In fact mysql2 what is used returns empty buffer in select queries, when sequelize catches that and returns null instead.

[sushantdhiman]

Ok so I have tested this change

User
  .sync({ force: true })
  .then(() => {
    return User.bulkCreate([{
      username: 'anc',
      data: Buffer.from('')
    }, {
      username: 'anc',
      data: null
    }]);
  })
  .then(() => {
    return User.findAll();
  })
  .then(users => {
    console.log(users[0].data, users[1].data);
  });

### Output
<Buffer > null

It seems MySQL2 now handles null case correctly, so as expected binary null should be returned as null but empty buffer should be returned as buffer.

If you can add a test around here https://github.com/sequelize/sequelize/blob/master/test/integration/model.test.js#L2526 It seems we already have a test for null case

sequelize/test/integration/model.test.js

Line 2562 in 5f7d69a

expect(user.data).to.be.null;

, so no need to add new test

Some related issues #8661 sidorares/node-mysql2#668

[sushantdhiman]

Remove BLOB function from this file, we will now go with mysql2 default