Difference between postgeSQL table contrains, sequelize options and sequelize validation?
For example:
What is the difference between:
title: { type: Sequelize.STRING, allowNull: false},
and
title: { type: Sequelize.STRING, validate: { notNull: true }
and
CREATE TABLE mytable( username TEXT NOT NULL )
In the documentation they say:
// setting allowNull to false will add NOT NULL to the column, which means an error will be
// thrown from the DB when the query is executed if the column is null. If you want to check that a value
// is not null before querying the DB, look at the validations section below.
Why would the error be thrown from the db yet the constrain is in a sequelize model definition? Why not just throw it from sequelize? What is the purpose of the model definition then? Another thing that is confusing me is why we need extra validation from the 'validate option' yet we have constrains in the model as well.
Also what will happen if we put a constrain in the postgreSQL table and not in sequelize model or vice versa?
I suppose that allowNull: false directly translates to NOT NULL constraint when this ORM creates tables.
From https://sequelize.org/v5/manual/models-definition.html
// setting allowNull to false will add NOT NULL to the column, which means an error will be
// thrown from the DB when the query is executed if the column is null.
That is, first and third snippets are equivalent, provided that tables are created with ORM.
Validation in the second snippet happens on the "client" side (that is, when you run your JS code). If you have validation only, but not a constraint in the database then you can set NULL values e.g. by using some other client. If you have a database constraint then no matter what client do you use, you can't set NULL value.
Related
I am using Dynamodb with nodejs for my reservation system. And Dynamoose as ORM. I have two tables i.e Table and Reservation. To create relation between them, I have added tableId attribute in Reservation which is of type Model type (of type Table type), as mentioned in the dyanmoose docs. Using the document.populate I am able to get the Table data through the tableId attribute from Reservation table. But how can I retrieve all Reservation for a Table? (Reservation and Table has one to many relation)?
These are my Model:
Table Model:
const tableSchema = new Schema ({
tableId: {
type: String,
required: true,
unique: true,
hashKey: true
},
name: {
type: String,
default: null
},
});
*Reservation Model:*
const reservationSchema = new Schema ({
id: {
type: Number,
required: true,
unique: true,
hashKey: true
},
tableId: table, \\as per doc attribute of Table (Model) type
date: {
type: String
}
});
This is how I retrieve table data from reservation model
reservationModel.scan().exec()
.then(posts => {
return posts.populate({
path: 'tableId',
model: 'Space'
});
})
.then(populatedPosts => {
console.log('pp',populatedPosts);
return {
allData: {
message: "Executedddd succesfully",
data: populatedPosts
}
}
})
Anyone please help to retrieve all Reservation data from Table??
As of v2.8.2, Dynamoose does not support this. Dynamoose is focused on one directional simple relationships. This is partly due to the fact that we discourage use of model.populate. It is important to note that model.populate does another completely separate request to DynamoDB. This increases the latency and decreases the performance of your application.
DynamoDB truly requires a shift in how you think about modeling your data compared to SQL. I recommend watching AWS re:Invent 2019: Data modeling with Amazon DynamoDB (CMY304) for a great explanation of how you can model your data in DynamoDB in a highly efficient manner.
At some point Dynamoose might add support for this, but it's really hard to say if we will.
If you truly want to do this, I'd recommend adding a global index to your tableId property in your reservation schema. Then you can run something like the following:
async function code(id) {
const reservation = await reservationModel.get(id);
const tables = await tableModel.query("tableId").eq(id).exec(); // This will be an array of `table` entries where `"tableId"=id`. Remember, it is required you add an index for this to work.
}
Remember, this will cause multiple calls to DynamoDB and isn't as efficient. I'd highly recommend watching the video I linked above to get more information about how to model your data in an more efficient manner.
Finally, I'd like to point out that your unique: true code does nothing. As seen in the Dynamoose Attribute Settings Documentation, unique is not a valid setting. In your case since you don't have a rangeKey, it's not possible for two items to have the same hashKey, so technically it's already a unique property based on that. However it is important to note that you can overwrite existing items when creating an item. You can set overwrite to false for document.save or Model.create to prevent that behavior and throw an error instead of overwriting your document.
I'm using sequelize 6.5.0. I created a simple model to do two rudimentary things: a) find records, b) create records. I'm having trouble creating records; specifically, ones with primary key. If I designate the column as primaryKey like so:
const Table = sequelize.define('table', {
id: {
type: DataTypes.UUID,
primaryKey: true
},
datum: {...}
...
and try to create a record like so:
Table.create({datum: 'abc'})
then it will try (and fail) to set the primary key with:
INSERT INTO "table" ("id","datum") VALUES ($1,$2) RETURNING ...;
which is 50% what I did not ask it to do. Now, I don't need this to happen since default value for id is already handled at the database level. So, the next natural move was to not designate id as primaryKey:
const Table = sequelize.define('table', {
id: {
type: DataTypes.UUID,
// primaryKey: true
},
datum: {...}
...
But now sequelize attempts to get smart and throws a tantrum:
Uncaught Error: A column called 'id' was added to the attributes of 'table' but not marked with 'primaryKey: true'
Q) How do I get sequelize to NOT handle primary key on create?
I think you can skip the id field in the definition altogether, and PostgreSQL will still have one
im trying to make a migration to alter all existing table fields to snake case, and future ones to be already written that way.
Up to now i've been doing this with
myTableField = {type: datatype.stmh, field: 'my_table_field'}
thing is i wanna stop doing this and for further upcoming fields i just need them to be set up directly with snake case.
Is there any way of doing this ? or i have to manually run an alter field for each?
Its possible to not rename every field to underscored in the model definition, via the underscored model option.
options.underscored - Converts all camelCased columns to underscored if true
options.underscoredAll - Converts camelCased model names to underscored table names if true
ex:
const User = sequelize.define('User', {
firstname: Sequelize.STRING,
lastname: Sequelize.STRING
},{
underscored:true})
Also on the CLI, we have the option to generate migrations with snakecase
>> sequelize model:generate --name User --attributes firstName:string,lastName:string --underscored
where
--underscored Use snake case for the timestamp's attribute names
But it only does it for the timestamp fields on the migration defs.
I don't understand the purpose of fields like unique and required in Mongoose schemas. In the case of unique, it appears that you have to write your own methods to query MongoDB to see if the value already exists. I suppose with 'required' Mongoose just needs to check if that value was passed in the constructor of a Mongoose model. But with unique, I don't understand the purpose of that.
userSchema = mongoose.Schema({
username: {
type: String,
unique: true,
required: true,
validate: [validation.usernameValidator, 'not a valid username']
},
...
in order to validate username, I have to create my own function = validation.usernameValidator to check MongoDB to see if the username already exists. So then what is the point of isUnique?
unique will create a MongoDB "unique" index on the property, preventing documents with the same value for that property to exist in the same collection.
However, since it's enforced by the database, the only way this works is by saving a document and catching the duplicate-key-error that MongoDB will return.
You can check for that error like so:
if (err && err.code === 11000) { ...duplicate... }
I'm new to sequelize and Node.js.
I coded for test sequelize, but error occured "ER_NO_SUCH_TABLE : Table 'db.node_tests' doesn't exist"
Error is very simple.
However, I want to get data from "node_test" table.
I think sequelize appends 's' character.
There is my source code.
var Sequelize = require('sequelize');
var sequelize = new Sequelize('db', 'user', 'pass');
var nodeTest = sequelize.define('node_test',
{ uid: Sequelize.INTEGER
, val: Sequelize.STRING} );
nodeTest.find({where:{uid:'1'}})
.success(function(tbl){
console.log(tbl);
});
I already create table "node_test", and inserted data using mysql client.
Does I misunderstood usage?
I found the answer my own question.
I appended Sequelize method option following. {define:{freezeTableName:true}}
Then sequelize not appends 's' character after table name.
Though the answer works nicely, I nowadays recommend the use of the tableName option when declaring the model:
sequelize.define('node_test', {
uid: Sequelize.INTEGER,
val: Sequelize.STRING
}, {
tableName: 'node_test'
});
http://docs.sequelizejs.com/manual/tutorial/models-definition.html
Sequelize is using by default the plural of the passed model name. So it will look for the table "node_tests" or "NodeTests". Also it can create the table for you if you want that.
nodeTest.sync().success(function() {
// here comes your find command.
})
Sync will try to create the table if it does not already exist. You can also drop the existing table and create a new one from scratch by using sync({ force: true }). Check the SQL commands on your command line for more details about what is going on.
When you define a model to an existing table, you need to set two options for sequelize to:
find your table name as-is and
not fret about sequelize's default columns updatedAt and createdAt that it expects.
Simply add both options like so:
var nodeTest = sequelize.define('node_test',
{ uid: Sequelize.INTEGER , val: Sequelize.STRING},
{ freezeTableName: true , timestamps: false} //add both options here
);
Note the options parameter:
sequelize.define('name_of_your_table',
{attributes_of_your_table_columns},
{options}
);
Missing either options triggers respective errors when using sequelize methods such as nodeTest.findAll().
> ER_NO_SUCH_TABLE //freezeTableName
> ER_BAD_FIELD_ERROR //timestamps
Alternatively, you can:
create a fresh table through sequelize. It will append "s" to the table name and create two timestamp columns as defaults or
use sequelize-auto, an awesome npm package to generate sequelize models from your existing database programmatically.
Here's the sequelize documentation for option configurations.
In my case, it was due to case. I was having:
sequelize.define('User', {
The correct way is to use lowercase:
sequelize.define('user', {