Writing Data

Mutations can insert, update, and remove data from database tables.

Inserting new documents

You can create new documents in the database with the db.insert method:

convex/tasks.ts

TS

import { mutation } from "./_generated/server";
import { v } from "convex/values";

export const createTask = mutation({
  args: { text: v.string() },
  handler: async (ctx, args) => {
    const taskId = await ctx.db.insert("tasks", { text: args.text });
    // do something with `taskId`
  },
});

The second argument to db.insert is a JavaScript object with data for the new document.

The same types of values that can be passed into and returned from queries and mutations can be written into the database. See Data Types for the full list of supported types.

The insert method returns a globally unique ID for the newly inserted document.

Updating existing documents

Given an existing document ID the document can be updated using the following methods:

1. The db.patch method will patch an existing document, shallow merging it with the given partial document. New fields are added. Existing fields are overwritten. Fields set to undefined are removed.

convex/tasks.ts

TS

import { mutation } from "./_generated/server";
import { v } from "convex/values";

export const updateTask = mutation({
  args: { id: v.id("tasks") },
  handler: async (ctx, args) => {
    const { id } = args;
    console.log(await ctx.db.get(id));
    // { text: "foo", status: { done: true }, _id: ... }

    // Add `tag` and overwrite `status`:
    await ctx.db.patch(id, { tag: "bar", status: { archived: true } });
    console.log(await ctx.db.get(id));
    // { text: "foo", tag: "bar", status: { archived: true }, _id: ... }

    // Unset `tag` by setting it to `undefined`
    await ctx.db.patch(id, { tag: undefined });
    console.log(await ctx.db.get(id));
    // { text: "foo", status: { archived: true }, _id: ... }
  },
});

2. The db.replace method will replace the existing document entirely, potentially removing existing fields:

convex/tasks.ts

TS

import { mutation } from "./_generated/server";
import { v } from "convex/values";

export const replaceTask = mutation({
  args: { id: v.id("tasks") },
  handler: async (ctx, args) => {
    const { id } = args;
    console.log(await ctx.db.get(id));
    // { text: "foo", _id: ... }

    // Replace the whole document
    await ctx.db.replace(id, { invalid: true });
    console.log(await ctx.db.get(id));
    // { invalid: true, _id: ... }
  },
});

Deleting documents

Given an existing document ID the document can be removed from the table with the db.delete method.

convex/tasks.ts

TS

import { mutation } from "./_generated/server";
import { v } from "convex/values";

export const deleteTask = mutation({
  args: { id: v.id("tasks") },
  handler: async (ctx, args) => {
    await ctx.db.delete(args.id);
  },
});

Bulk inserts or updates

If you are used to SQL you might be looking for some sort of bulk insert or bulk update statement. In Convex the entire mutation function is automatically a single transaction.

You can just insert or update in a loop in the mutation function. Convex queues up all database changes in the function and executes them all in a single transaction when the function ends, leading to a single efficient change to the database.

/**
 * Bulk insert multiple products into the database.
 *
 * Equivalent to the SQL:
 * ```sql
 * INSERT INTO products (product_id, product_name, category, price, in_stock)
 * VALUES
 *     ('Laptop Pro', 'Electronics', 1299.99, true),
 *     ('Wireless Mouse', 'Electronics', 24.95, true),
 *     ('Ergonomic Keyboard', 'Electronics', 89.50, true),
 *     ('Ultra HD Monitor', 'Electronics', 349.99, false),
 *     ('Wireless Headphones', 'Audio', 179.99, true);
 * ```
 */
export const bulkInsertProducts = mutation({
  args: {
    products: v.array(
      v.object({
        product_name: v.string(),
        category: v.string(),
        price: v.number(),
        in_stock: v.boolean(),
      }),
    ),
  },
  handler: async (ctx, args) => {
    const { products } = args;

    // Insert in a loop. This is efficient because Convex queues all the changes
    // to be executed in a single transaction when the mutation ends.
    for (const product of products) {
      const id = await ctx.db.insert("products", {
        product_name: product.product_name,
        category: product.category,
        price: product.price,
        in_stock: product.in_stock,
      });
    }
  },
});

Migrations

Database migrations are done through the migration component. The component is designed to run online migrations to safely evolve your database schema over time. It allows you to resume from failures, and validate changes with dry runs.

Convex component

Migrations

Framework for long running data migrations of live data.

Write performance and limits

To prevent accidental writes of large amounts of records, queries and mutations enforce limits detailed here.