Inserting multiple records with pg-promise - node.js

Question

I have a scenario in which I need to insert multiple records. I have a table structure like id (it's fk from other table), key(char), value(char). The input which needs to be saved would be array of above data. example:
I have some array objects like:
lst = [];
obj = {};
obj.id= 123;
obj.key = 'somekey';
obj.value = '1234';
lst.push(obj);
obj = {};
obj.id= 123;
obj.key = 'somekey1';
obj.value = '12345';
lst.push(obj);
In MS SQL, I would have created TVP and passed it. I don't know how to achieve in postgres.
So now what I want to do is save all the items from the list in single query in postgres sql, using pg-promise library. I'm not able to find any documentation / understand from documentation. Any help appreciated. Thanks.

Answer 1

I am the author of pg-promise.
There are two ways to insert multiple records. The first, and most typical way is via a transaction, to make sure all records are inserted correctly, or none of them.
With pg-promise it is done in the following way:
db.tx(t => {
const queries = lst.map(l => {
return t.none('INSERT INTO table(id, key, value) VALUES(${id}, ${key}, ${value})', l);
});
return t.batch(queries);
})
.then(data => {
// SUCCESS
// data = array of null-s
})
.catch(error => {
// ERROR
});
You initiate a transaction with method tx, then create all INSERT query promises, and then resolve them all as a batch.
The second approach is by concatenating all insert values into a single INSERT query, which I explain in detail in Performance Boost. See also: Multi-row insert with pg-promise.
For more examples see Tasks and Transactions.
Addition
It is worth pointing out that in most cases we do not insert a record id, rather have it generated automatically. Sometimes we want to get the new id-s back, and in other cases we don't care.
The examples above resolve with an array of null-s, because batch resolves with an array of individual results, and method none resolves with null, according to its API.
Let's assume that we want to generate the new id-s, and that we want to get them all back. To accomplish this we would change the code to the following:
db.tx(t => {
const queries = lst.map(l => {
return t.one('INSERT INTO table(key, value) VALUES(${key}, ${value}) RETURNING id',
l, a => +a.id);
});
return t.batch(queries);
})
.then(data => {
// SUCCESS
// data = array of new id-s;
})
.catch(error => {
// ERROR
});
i.e. the changes are:
we do not insert the id values
we replace method none with one, to get one row/object from each insert
we append RETURNING id to the query to get the value
we add a => +a.id to do the automatic row transformation. See also pg-promise returns integers as strings to understand what that + is for.
UPDATE-1
For a high-performance approach via a single INSERT query see Multi-row insert with pg-promise.
UPDATE-2
A must-read article: Data Imports.