PostgreSQL multi-row updates in Node.js

Question

As i already found here On Stackoverflow it is possible to update multiple rows in one query by doing something like this

update test as t set
    column_a = c.column_a,
    column_c = c.column_c
from (values
    ('123', 1, '---'),
    ('345', 2, '+++')  
) as c(column_b, column_a, column_c) 
where c.column_b = t.column_b;

special thanks to @Roman Pekar for the clear answer.

Now i'm trying to merge this way of updating with querying to a postgreSQL database in NodeJS.

Here is a snipped of my code:

var requestData = [
    {id: 1, value: 1234}
    {id: 2, value: 5678}
    {id: 3, value: 91011}
]


client.connect(function (err) {
    if (err) throw err;

client.query(buildStatement(requestData), function (err, result) {
    if (err) throw err;

    res.json(result.rows);

    client.end(function (err) {
        if (err) throw err;
    });
});
});


var buildStatement = function(requestData) {
var params = [];
var chunks = [];

for(var i = 0; i < requestData.length; i++) {

    var row = requestData[i];
    var valuesClause = [];

    params.push(row.id);
    valuesClause.push('$' + params.length);
    params.push(row.value);
    valuesClause.push('$' + params.length);

    chunks.push('(' + valuesClause.join(', ') + ')');

}

return {
    text: 'UPDATE fit_ratios as f set ratio_budget = c.ratio_budget from (VALUES ' +  chunks.join(', ') + ') as c(ratio_label, ratio_budget) WHERE c.ratio_label = f.ratio_label', values: params
        }
}

i don't get an error but it doesn't update my table, i don't really know what goes wrong here. Perhaps a syntax error in my query code? I just don't find any specific examples of multiple row querying when updating in NodeJS pg package

Answer 1

The example below is based on library pg-promise, and its method helpers.update:

// library initialization, usually placed in its own module:
const pgp = require('pg-promise')({
    capSQL: true // capitalize all generated SQL
});

const db = pgp(/*your connection details*/);

// records to be updated:
const updateData = [
    {id: 1, value: 1234},
    {id: 2, value: 5678},
    {id: 3, value: 91011}
];

// declare your ColumnSet once, and then reuse it:
const cs = new pgp.helpers.ColumnSet(['?id', 'value'], {table: 'fit_ratios'});

// generating the update query where it is needed:
const update = pgp.helpers.update(updateData, cs) + ' WHERE v.id = t.id';
//=> UPDATE "fit_ratios" AS t SET "value"=v."value"
//   FROM (VALUES(1,1234),(2,5678),(3,91011))
//   AS v("id","value") WHERE v.id = t.id

// executing the query:
await db.none(update);

This method of generating multi-row updates can be characterized as:

• very fast, as it relies on type ColumnSet that implements smart caching for query generation
• completely safe, as all data types are going through the library's query formatting engine to make sure everything is formatted and escaped correctly.
• very flexible, due to advanced ColumnConfig syntax supported for the columns definition.
• very easy to use, due to the simplified interface implemented by pg-promise.

---

Note that we use ? in front of column id to indicate that the column is part of the condition, but not to be updated. For complete column syntax see class Column and ColumnConfig structure.

---

Related question: Multi-row insert with pg-promise.