DEV Community: Varun Hegde

How do i convert the following code to transaction in Node.js?

Varun Hegde — Wed, 13 Jan 2021 07:12:49 +0000

I have written this async function which calls bunch of async functions inside which executes INSERT or SELECT statements and each function needs the output from the previous one. There's a lot of of INSERT operation so its taking lot of time.

code --
async writeDataseq(bno, pno, textArr) {
const pageNoTablePacket = await this.writeToPageNoTable(bno, pno);
try {
let pgId = pageNoTablePacket.insertId;
if (pgId == 0) {
pgId = await this.getPgId(bno, pno);
}

for (let index = 0; index < textArr.length; index++) {
let leftWord = null;
let rightWord = null;
let word = textArr[index];
if (index - 1 >= 0) {
leftWord = textArr[index - 1];
}
if (index + 1 < textArr.length) {
rightWord = textArr[index + 1];
}
const wordPacket = await this.writeWordToDb(word);
let wordId = wordPacket.insertId;
if (wordId == 0) {
wordId = await this.getWordId(word);
}
const wordInstPacket = await this.writeWordInst(wordId, pgId);
const wordContextPacket = await this.writeWordContext(
wordInstId,
leftWord,
rightWord
);
}
//every operation finished
return 'everything done successfully';
} catch (error) {
throw Error(error);
}
}

I am using Mysql database and am using node-mysql driver. I want to commit everything at once in the end to make it fast. How can I achieve this ?

Thanks in advance.

I am trying to match this text with regexp but getting error

Varun Hegde — Thu, 26 Nov 2020 04:24:41 +0000

string : ----------------Page (0) Break----------------
(it can have any number inside parenthesis)

pattern : /?<=-{16}Page ()(\d+)(?=) Break-{16})/g

usage :

if(line.search( /?<=-{16}Page ()(\d+)(?=) Break-{16})/g )!=-1)
{
console.log(line);
}

error : SyntaxError: Invalid regular expression: /?<=-{16}Page ()(\d+)(?=) Break-{16})/: Nothing to repeat

Any help would be appreciated.
Thank You

Asynchronous Javascript

Varun Hegde — Thu, 29 Oct 2020 04:17:45 +0000

I have some trivial doubts regarding Asynchronous functions.

1) When await keyword is encountered in async function, what does js exactly do ?
does it skip the whole function and goes to next next instruction outside the function or will it try to execute rest of the code in async ( i personally think the first one as whatever inside a async func is supposed to be executed after the asynchronous instruction)

2) Javascript has single thread and event based model. so if it encounters asynchronous code, i have read that it works in the background executing other instruction. what does executing in the background mean (if only it has single thread)?

3) If in a code every instruction is depends on result of previous async function ,doesn’t executing in both synchronously and asynchronously becomes same ?

Kindly answer these question whenever you have time.

Thanks in advance.

customizing the flask admin page

Varun Hegde — Tue, 15 Sep 2020 09:50:49 +0000

I want add another button with those delete and edit icons in flask admin template and want to send that row data for some route as post request. i know to that i have to edit in admin/model/list.html template. But i am not getting how to add this functionalities.
Please help.
Thanks in advance.

Getting Error in SqlAlchemy

Varun Hegde — Fri, 28 Aug 2020 05:30:58 +0000

I was trying to define one to many relationship in sqlalchemy in flask.
This are my model.

class Storm(db.Model):
    __tablename__='storm'
    __table_args__ (
        db.UniqueConstraint('name','year'),
    )
    id=db.Column(db.Integer,primary_key=True)
    name=db.Column(db.String(50),nullable=False)
    year=db.Column(db.Integer,nullable=False)
    cat=db.Column(db.String(50))
    pos=db.realationship('Position',backref='storm_info',lazy=True)

    def __repr__(self):
        return '<storm_name : {},storm_year : {}>'.format(self.name,self.year)

class Position(db.Model):
    lat=db.Column(db.Float)
    longi=db.Column(db.Float)
    storm_id=db.Column(db.Integer,db.ForeignKey('storm.id'),nullable=False)
    pressure-db.Column(db.Float)

I want compound uniqueness for name and year.
but i am getting this error -
NameError: name 'table_args' is not defined.
can anyone please suggest what is the problem and how i can define it ?
and whats the difference between this and defining by declarative model?
Thanks in advance

Config Error with Mongodb-Atlas and flask-MongoAlchemy

Varun Hegde — Sat, 15 Aug 2020 10:50:43 +0000

I did put password of that user in the field and i have tried all possible combination with dbname.I dont know which dbname it is referring to. I have searched many places, didnt get any answers. Can some one please help me how to configure.

app.config['DEBUG']=True
app.config['MONGOALCHEMY_CONNECTION_STRING']='mongodb+srv://user:
@test .usvae.mongodb.net/?retryWrites=true&w=majority'
db=MongoAlchemy(app)
This is my configeration. This is the error i am getting

raise ImproperlyConfiguredError("You should provide a database name " flask_mongoalchemy.ImproperlyConfiguredError: You should provide a database name (the MONGOALCHEMY_DATABASE setting)

Thanks in advance

Looking for projects

Varun Hegde — Mon, 27 Jul 2020 13:02:45 +0000

I recently learnt javascript and I know html ,css and bootstrap I wanted a beginner friendly projects (open source is even better) where I can learn more.
Please guide me.
Thank in advance