convex-migrations

name convex-migrations displayName Convex Migrations description Schema migration strategies for evolving applications including adding new fields, backfilling data, removing deprecated fields, index migrations, and zero-downtime migration patterns version 1.0.0 author Convex tags ["convex","migrations","schema","database","data-modeling"] Convex Migrations Evolve your Convex database schema safely with patterns for adding fields, backfilling data, removing deprecated fields, and maintaining zero-downtime deployments. Documentation Sources Before implementing, do not assume; fetch the latest documentation: Primary: https://docs.convex.dev/database/schemas Schema Overview: https://docs.convex.dev/database Migration Patterns: https://stack.convex.dev/migrate-data-postgres-to-convex For broader context: https://docs.convex.dev/llms.txt Instructions Migration Philosophy Convex handles schema evolution differently than traditional databases: No explicit migration files or commands Schema changes deploy instantly with npx convex dev Existing data is not automatically transformed Use optional fields and backfill mutations for safe migrations Adding New Fields Start with optional fields, then backfill: // Step 1: Add optional field to schema // convex/schema.ts import { defineSchema, defineTable } from "convex/server" ; import { v } from "convex/values" ; export default defineSchema ({ users : defineTable ({ name : v. string (), email : v. string (), // New field - start as optional avatarUrl : v. optional (v. string ()), }), }); // Step 2: Update code to handle both cases // convex/users.ts import { query } from "./_generated/server" ; import { v } from "convex/values" ; export const getUser = query ({ args : { userId : v. id ( "users" ) }, returns : v. union ( v. object ({ _id : v. id ( "users" ), name : v. string (), email : v. string (), avatarUrl : v. union (v. string (), v. null ()), }), v. null () ), handler : async (ctx, args) => { const user = await ctx. db . get (args. userId ); if (!user) return null ; return { _id : user. _id , name : user. name , email : user. email , // Handle missing field gracefully avatarUrl : user. avatarUrl ?? null , }; }, }); // Step 3: Backfill existing documents // convex/migrations.ts import { internalMutation } from "./_generated/server" ; import { internal } from "./_generated/api" ; import { v } from "convex/values" ; const BATCH_SIZE = 100 ; export const backfillAvatarUrl = internalMutation ({ args : { cursor : v. optional (v. string ()), }, returns : v. object ({ processed : v. number (), hasMore : v. boolean (), }), handler : async (ctx, args) => { const result = await ctx. db . query ( "users" ) . paginate ({ numItems : BATCH_SIZE , cursor : args. cursor ?? null }); let processed = 0 ; for ( const user of result. page ) { // Only update if field is missing if (user. avatarUrl === undefined ) { await ctx. db . patch (user. _id , { avatarUrl : generateDefaultAvatar (user. name ), }); processed++; } } // Schedule next batch if needed if (!result. isDone ) { await ctx. scheduler . runAfter ( 0 , internal. migrations . backfillAvatarUrl , { cursor : result. continueCursor , }); } return { processed, hasMore : !result. isDone , }; }, }); function generateDefaultAvatar ( name : string ): string { return `https://api.dicebear.com/7.x/initials/svg?seed= ${ encodeURIComponent (name)} ` ; } // Step 4: After backfill completes, make field required // convex/schema.ts export default defineSchema ({ users : defineTable ({ name : v. string (), email : v. string (), avatarUrl : v. string (), // Now required }), }); Removing Fields Remove field usage before removing from schema: // Step 1: Stop using the field in queries and mutations // Mark as deprecated in code comments // Step 2: Remove field from schema (make optional first if needed) // convex/schema.ts export default defineSchema ({ posts : defineTable ({ title : v. string (), content : v. string (), authorId : v. id ( "users" ), // legacyField: v.optional(v.string()), // Remove this line }), }); // Step 3: Optionally clean up existing data // convex/migrations.ts export const removeDeprecatedField = internalMutation ({ args : { cursor : v. optional (v. string ()), }, returns : v. null (), handler : async (ctx, args) => { const result = await ctx. db . query ( "posts" ) . paginate ({ numItems : 100 , cursor : args. cursor ?? null }); for ( const post of result. page ) { // Use replace to remove the field entirely const { legacyField, ...rest } = post as typeof post & { legacyField ?: string }; if (legacyField !== undefined ) { await ctx. db . replace (post. _id , rest); } } if (!result. isDone ) { await ctx. scheduler . runAfter ( 0 , internal. migrations . removeDeprecatedField , { cursor : result. continueCursor , }); } return null ; }, }); Renaming Fields Renaming requires copying data to new field, then removing old: // Step 1: Add new field as optional // convex/schema.ts export default defineSchema ({ users : defineTable ({ userName : v. string (), // Old field displayName : v. optional (v. string ()), // New field }), }); // Step 2: Update code to read from new field with fallback export const getUser = query ({ args : { userId : v. id ( "users" ) }, returns : v. object ({ _id : v. id ( "users" ), displayName : v. string (), }), handler : async (ctx, args) => { const user = await ctx. db . get (args. userId ); if (!user) throw new Error ( "User not found" ); return { _id : user. _id , // Read new field, fall back to old displayName : user. displayName ?? user. userName , }; }, }); // Step 3: Backfill to copy data export const backfillDisplayName = internalMutation ({ args : { cursor : v. optional (v. string ()) }, returns : v. null (), handler : async (ctx, args) => { const result = await ctx. db . query ( "users" ) . paginate ({ numItems : 100 , cursor : args. cursor ?? null }); for ( const user of result. page ) { if (user. displayName === undefined ) { await ctx. db . patch (user. _id , { displayName : user. userName , }); } } if (!result. isDone ) { await ctx. scheduler . runAfter ( 0 , internal. migrations . backfillDisplayName , { cursor : result. continueCursor , }); } return null ; }, }); // Step 4: After backfill, update schema to make new field required // and remove old field export default defineSchema ({ users : defineTable ({ // userName removed displayName : v. string (), }), }); Adding Indexes Add indexes before using them in queries: // Step 1: Add index to schema // convex/schema.ts export default defineSchema ({ posts : defineTable ({ title : v. string (), authorId : v. id ( "users" ), publishedAt : v. optional (v. number ()), status : v. string (), }) . index ( "by_author" , [ "authorId" ]) // New index . index ( "by_status_and_published" , [ "status" , "publishedAt" ]), }); // Step 2: Deploy schema change // Run: npx convex dev // Step 3: Now use the index in queries export const getPublishedPosts = query ({ args : {}, returns : v. array (v. object ({ _id : v. id ( "posts" ), title : v. string (), publishedAt : v. number (), })), handler : async (ctx) => { const posts = await ctx. db . query ( "posts" ) . withIndex ( "by_status_and_published" , ( q ) => q. eq ( "status" , "published" ) ) . order ( "desc" ) . take ( 10 ); return posts . filter ( ( p ) => p. publishedAt !== undefined ) . map ( ( p ) => ({ _id : p. _id , title : p. title , publishedAt : p. publishedAt !, })); }, }); Changing Field Types Type changes require careful migration: // Example: Change from string to number for a "priority" field // Step 1: Add new field with new type // convex/schema.ts export default defineSchema ({ tasks : defineTable ({ title : v. string (), priority : v. string (), // Old: "low", "medium", "high" priorityLevel : v. optional (v. number ()), // New: 1, 2, 3 }), }); // Step 2: Backfill with type conversion export const migratePriorityToNumber = internalMutation ({ args : { cursor : v. optional (v. string ()) }, returns : v. null (), handler : async (ctx, args) => { const result = await ctx. db . query ( "tasks" ) . paginate ({ numItems : 100 , cursor : args. cursor ?? null }); const priorityMap : Record < string , number > = { low : 1 , medium : 2 , high : 3 , }; for ( const task of result. page ) { if (task. priorityLevel === undefined ) { await ctx. db . patch (task. _id , { priorityLevel : priorityMap[task. priority ] ?? 1 , }); } } if (!result. isDone ) { await ctx. scheduler . runAfter ( 0 , internal. migrations . migratePriorityToNumber , { cursor : result. continueCursor , }); } return null ; }, }); // Step 3: Update code to use new field export const getTask = query ({ args : { taskId : v. id ( "tasks" ) }, returns : v. object ({ _id : v. id ( "tasks" ), title : v. string (), priorityLevel : v. number (), }), handler : async (ctx, args) => { const task = await ctx. db . get (args. taskId ); if (!task) throw new Error ( "Task not found" ); const priorityMap : Record < string , number > = { low : 1 , medium : 2 , high : 3 , }; return { _id : task. _id , title : task. title , priorityLevel : task. priorityLevel ?? priorityMap[task. priority ] ?? 1 , }; }, }); // Step 4: After backfill, update schema export default defineSchema ({ tasks : defineTable ({ title : v. string (), // priority field removed priorityLevel : v. number (), }), }); Migration Runner Pattern Create a reusable migration system: // convex/schema.ts import { defineSchema, defineTable } from "convex/server" ; import { v } from "convex/values" ; export default defineSchema ({ migrations : defineTable ({ name : v. string (), startedAt : v. number (), completedAt : v. optional (v. number ()), status : v. union ( v. literal ( "running" ), v. literal ( "completed" ), v. literal ( "failed" ) ), error : v. optional (v. string ()), processed : v. number (), }). index ( "by_name" , [ "name" ]), // Your other tables... }); // convex/migrations.ts import { internalMutation, internalQuery } from "./_generated/server" ;