Convex schema validator

Produces a convex/schema.ts that types every document, indexes every query path, and passes validation against the data already in the database. The one rule: every withIndex in a function needs a matching .index() here, named after its fields, queried in field order.

When to reach for this

• Creating a new table or adding a field to an existing one
• A query uses .filter() and needs an index instead
• Deciding whether to embed an object or link with v.id
• Modeling a document that comes in several shapes
• npx convex dev fails with a schema validation error

Schema skeleton

// 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(),
    avatarUrl: v.optional(v.string()),
  }).index("by_email", ["email"]),

  tasks: defineTable({
    userId: v.id("users"),
    title: v.string(),
    completed: v.boolean(),
    priority: v.union(v.literal("low"), v.literal("medium"), v.literal("high")),
  })
    .index("by_userId", ["userId"])
    .index("by_userId_and_completed", ["userId", "completed"]),
});

defineTable takes either an object of field validators or a single v.union of v.object validators (see discriminated unions). Every table gets _id and _creationTime for free. Do not declare them.

Validators

Validator	TypeScript type	Note
v.string()	string	UTF-8, under 1 MB
v.number()	number	Float64. Use for timestamps and counts
v.boolean()	boolean
v.null()	null	undefined is not a Convex value. Return null instead
v.int64()	bigint	Not v.bigint(), which is deprecated
v.bytes()	ArrayBuffer	Under 1 MB
v.id("table")	Id<"table">	Typed reference. Convex does not enforce that the target exists
v.array(t)	T[]	At most 8192 items
v.object({...})	{...}	At most 1024 entries. Keys cannot start with $ or _
v.record(k, t)	Record<K, T>	Dynamic ASCII keys. No v.map or v.set
v.union(a, b)	A | B	Use v.literal members for enums
v.literal("x")	"x"
v.optional(t)	T | undefined	Field may be absent
v.any()	any	Last resort. Loses type safety and validation

Optional versus nullable

v.optional means the key may be missing from the document. v.union(t, v.null()) means the key is always present and may hold null. They are different at validation time.

items: defineTable({
  description: v.optional(v.string()),           // may be absent
  deletedAt: v.union(v.number(), v.null()),       // always present, may be null
  notes: v.optional(v.union(v.string(), v.null())), // either
}),

Use v.optional for fields added after the table had data. Use v.union(..., v.null()) when "explicitly cleared" carries meaning.

Discriminated unions

For a table whose documents come in several shapes, pass a v.union of v.object validators to defineTable. Each member has the same literal key so TypeScript narrows on it.

events: defineTable(
  v.union(
    v.object({
      kind: v.literal("signup"),
      userId: v.id("users"),
      email: v.string(),
    }),
    v.object({
      kind: v.literal("purchase"),
      userId: v.id("users"),
      orderId: v.id("orders"),
      amount: v.number(),
    }),
  ),
).index("by_kind", ["kind"]),

Put the discriminant (kind) first in any index on a union table so queries can scope to one shape. Prefer this over one wide object full of v.optional fields.

Indexes

Naming and field order

Name the index after its fields in order: by_field1_and_field2. Querying must follow the same order: equality on a prefix of the fields, then at most one range on the next field.

messages: defineTable({
  channelId: v.id("channels"),
  authorId: v.id("users"),
  sentAt: v.number(),
})
  .index("by_channelId", ["channelId"])
  .index("by_channelId_and_authorId", ["channelId", "authorId"])
  .index("by_channelId_and_sentAt", ["channelId", "sentAt"]),

// Valid: equality on channelId, range on sentAt
await ctx.db
  .query("messages")
  .withIndex("by_channelId_and_sentAt", (q) =>
    q.eq("channelId", args.channelId).gt("sentAt", args.since),
  )
  .order("desc")
  .take(50);

You cannot skip channelId and filter on sentAt alone with that index. Add by_sentAt if that query exists. _creationTime is appended to every index automatically, so results within an equal prefix sort by creation time.

Reserved names: by_id and by_creation_time. Limits: 32 indexes per table, 16 fields per index.

When to add one

• Any field a function passes to withIndex, .eq, or a range comparison
• Every foreign key (userId, channelId, orgId) on the child table
• The sort field for a paginated list, prefixed by the scoping field
• Not for fields you only read after fetching the document
• Not for tiny tables where a .collect() then in memory filter is fine

If a query uses .filter(), that is the signal to add an index and switch to withIndex.

Relationships

Link documents with v.id("table") on the child. Do not nest growing arrays of objects inside the parent.

// Good: one to many via a foreign key
posts: defineTable({
  authorId: v.id("users"),
  title: v.string(),
}).index("by_authorId", ["authorId"]),

comments: defineTable({
  postId: v.id("posts"),
  authorId: v.id("users"),
  body: v.string(),
}).index("by_postId", ["postId"]),

// Many to many via a join table
postTags: defineTable({
  postId: v.id("posts"),
  tagId: v.id("tags"),
})
  .index("by_postId", ["postId"])
  .index("by_tagId", ["tagId"]),

Embed with v.object or a small v.array only when the data is bounded, always loaded with the parent, and updated together. A user's settings object is a good embed. A user's posts array is not: it hits the 8192 item cap and every post edit rewrites the user document.

System fields

_id: Id<"table"> and _creationTime: number (ms since epoch) exist on every document. Include them in return validators when a function returns whole documents:

returns: v.array(
  v.object({
    _id: v.id("tasks"),
    _creationTime: v.number(),
    userId: v.id("users"),
    title: v.string(),
    completed: v.boolean(),
  }),
),

Do not add your own createdAt unless you need a value that differs from insertion time.

Search and vector indexes

Declared on the table like regular indexes. filterFields must be top level fields.

articles: defineTable({
  title: v.string(),
  body: v.string(),
  category: v.string(),
  embedding: v.array(v.number()),
})
  .searchIndex("search_body", {
    searchField: "body",
    filterFields: ["category"],
  })
  .vectorIndex("by_embedding", {
    vectorField: "embedding",
    dimensions: 1536,
    filterFields: ["category"],
  }),

Query search indexes with withSearchIndex in queries. Vector search runs only in actions via ctx.vectorSearch.

Common mistakes

Mistake	Why it breaks	Do instead
withIndex("by_userId") with no matching .index()	Deploy fails	Declare the index in the schema first
Index named by_user on ["userId", "status"]	Hides what it covers, easy to misuse	by_userId_and_status
Querying status on by_userId_and_status without userId	Index prefix rule	Add by_status or include userId
Adding newField: v.string() to a table with rows	Existing documents fail validation	v.optional, backfill, then require
posts: v.array(v.object(...)) on users	8192 cap, write conflicts on every edit	Separate posts table with by_authorId
v.bigint()	Deprecated	v.int64()
Declaring _id or _creationTime in defineTable	Rejected	They are automatic
v.any() to move fast	No validation, no types	Model the shape, or a v.union of the real cases
v.union(v.string(), v.null()) for a new field	Old documents lack the key entirely	v.optional(v.string())
Storing a Date	Not a Convex value	v.number() ms timestamp

Checklist

• Schema lives in convex/schema.ts and exports defineSchema(...) as default
• Every table has explicit field validators, no v.any() unless justified
• Every withIndex call in convex/ has a matching .index() with fields in the name
• Foreign keys are v.id("table") with an index on the child table
• No unbounded arrays of objects embedded in a parent document
• Fields added to tables with data are v.optional
• Enums and polymorphic shapes use v.union of v.literal or v.object members
• Return validators include _id and _creationTime when returning whole documents
• npx convex dev pushes without a schema validation error

Docs

• https://docs.convex.dev/llms.txt
• https://docs.convex.dev/database/schemas
• https://docs.convex.dev/database/indexes
• https://docs.convex.dev/database/types
• https://docs.convex.dev/database/reading-data