Convex Schema Validator Skill

Convex Schema Validator

Define and validate database schemas in Convex with proper typing, index configuration, optional fields, unions, and strategies for schema migrations.

Documentation Sources

Before implementing, do not assume; fetch the latest documentation:

Primary: https://docs.convex.dev/database/schemas
Indexes: https://docs.convex.dev/database/indexes
Data Types: https://docs.convex.dev/database/types
For broader context: https://docs.convex.dev/llms.txt

Instructions

Basic Schema Definition

// 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()),
    createdAt: v.number(),
  }),
  
  tasks: defineTable({
    title: v.string(),
    description: v.optional(v.string()),
    completed: v.boolean(),
    userId: v.id("users"),
    priority: v.union(
      v.literal("low"),
      v.literal("medium"),
      v.literal("high")
    ),
  }),
});

Validator Types

| Validator | TypeScript Type | Example | |-----------|----------------|---------| | v.string() | string | "hello" | | v.number() | number | 42, 3.14 | | v.boolean() | boolean | true, false | | v.null() | null | null | | v.int64() | bigint | 9007199254740993n | | v.bytes() | ArrayBuffer | Binary data | | v.id("table") | Id<"table"> | Document reference | | v.array(v) | T[] | [1, 2, 3] | | v.object({}) | { ... } | { name: "..." } | | v.optional(v) | T \| undefined | Optional field | | v.union(...) | T1 \| T2 | Multiple types | | v.literal(x) | "x" | Exact value | | v.any() | any | Any value | | v.record(k, v) | Record<K, V> | Dynamic keys |

Index Configuration

export default defineSchema({
  messages: defineTable({
    channelId: v.id("channels"),
    authorId: v.id("users"),
    content: v.string(),
    sentAt: v.number(),
  })
    // Single field index
    .index("by_channel", ["channelId"])
    // Compound index
    .index("by_channel_and_author", ["channelId", "authorId"])
    // Index for sorting
    .index("by_channel_and_time", ["channelId", "sentAt"]),
    
  // Full-text search index
  articles: defineTable({
    title: v.string(),
    body: v.string(),
    category: v.string(),
  })
    .searchIndex("search_content", {
      searchField: "body",
      filterFields: ["category"],
    }),
});

Complex Types

export default defineSchema({
  // Nested objects
  profiles: defineTable({
    userId: v.id("users"),
    settings: v.object({
      theme: v.union(v.literal("light"), v.literal("dark")),
      notifications: v.object({
        email: v.boolean(),
        push: v.boolean(),
      }),
    }),
  }),

  // Arrays of objects
  orders: defineTable({
    customerId: v.id("users"),
    items: v.array(v.object({
      productId: v.id("products"),
      quantity: v.number(),
      price: v.number(),
    })),
    status: v.union(
      v.literal("pending"),
      v.literal("processing"),
      v.literal("shipped"),
      v.literal("delivered")
    ),
  }),

  // Record type for dynamic keys
  analytics: defineTable({
    date: v.string(),
    metrics: v.record(v.string(), v.number()),
  }),
});

Discriminated Unions

export default defineSchema({
  events: defineTable(
    v.union(
      v.object({
        type: v.literal("user_signup"),
        userId: v.id("users"),
        email: v.string(),
      }),
      v.object({
        type: v.literal("purchase"),
        userId: v.id("users"),
        orderId: v.id("orders"),
        amount: v.number(),
      }),
      v.object({
        type: v.literal("page_view"),
        sessionId: v.string(),
        path: v.string(),
      })
    )
  ).index("by_type", ["type"]),
});

Optional vs Nullable Fields

export default defineSchema({
  items: defineTable({
    // Optional: field may not exist
    description: v.optional(v.string()),
    
    // Nullable: field exists but can be null
    deletedAt: v.union(v.number(), v.null()),
    
    // Optional and nullable
    notes: v.optional(v.union(v.string(), v.null())),
  }),
});

Index Naming Convention

Always include all indexed fields in the index name:

export default defineSchema({
  posts: defineTable({
    authorId: v.id("users"),
    categoryId: v.id("categories"),
    publishedAt: v.number(),
    status: v.string(),
  })
    // Good: descriptive names
    .index("by_author", ["authorId"])
    .index("by_author_and_category", ["authorId", "categoryId"])
    .index("by_category_and_status", ["categoryId", "status"])
    .index("by_status_and_published", ["status", "publishedAt"]),
});

Schema Migration Strategies

Adding New Fields

// Before
users: defineTable({
  name: v.string(),
  email: v.string(),
})

// After - add as optional first
users: defineTable({
  name: v.string(),
  email: v.string(),
  avatarUrl: v.optional(v.string()), // New optional field
})

Backfilling Data

// convex/migrations.ts
import { internalMutation } from "./_generated/server";
import { v } from "convex/values";

export const backfillAvatars = internalMutation({
  args: {},
  returns: v.number(),
  handler: async (ctx) => {
    const users = await ctx.db
      .query("users")
      .filter((q) => q.eq(q.field("avatarUrl"), undefined))
      .take(100);

    for (const user of users) {
      await ctx.db.patch(user._id, {
        avatarUrl: `https://api.dicebear.com/7.x/initials/svg?seed=${user.name}`,
      });
    }

    return users.length;
  },
});

Making Optional Fields Required

// Step 1: Backfill all null values
// Step 2: Update schema to required
users: defineTable({
  name: v.string(),
  email: v.string(),
  avatarUrl: v.string(), // Now required after backfill
})

Examples

Complete E-commerce Schema

// convex/schema.ts
import { defineSchema, defineTable } from "convex/server";
import { v } from "convex/values";

export default defineSchema({
  users: defineTable({
    email: v.string(),
    name: v.string(),
    role: v.union(v.literal("customer"), v.literal("admin")),
    createdAt: v.number(),
  })
    .index("by_email", ["email"])
    .index("by_role", ["role"]),

  products: defineTable({
    name: v.string(),
    description: v.string(),
    price: v.number(),
    category: v.string(),
    inventory: v.number(),
    isActive: v.boolean(),
  })
    .index("by_category", ["category"])
    .index("by_active_and_category", ["isActive", "category"])
    .searchIndex("search_products", {
      searchField: "name",
      filterFields: ["category", "isActive"],
    }),

  orders: defineTable({
    userId: v.id("users"),
    items: v.array(v.object({
      productId: v.id("products"),
      quantity: v.number(),
      priceAtPurchase: v.number(),
    })),
    total: v.number(),
    status: v.union(
      v.literal("pending"),
      v.literal("paid"),
      v.literal("shipped"),
      v.literal("delivered"),
      v.literal("cancelled")
    ),
    shippingAddress: v.object({
      street: v.string(),
      city: v.string(),
      state: v.string(),
      zip: v.string(),
      country: v.string(),
    }),
    createdAt: v.number(),
    updatedAt: v.number(),
  })
    .index("by_user", ["userId"])
    .index("by_user_and_status", ["userId", "status"])
    .index("by_status", ["status"]),

  reviews: defineTable({
    productId: v.id("products"),
    userId: v.id("users"),
    rating: v.number(),
    comment: v.optional(v.string()),
    createdAt: v.number(),
  })
    .index("by_product", ["productId"])
    .index("by_user", ["userId"]),
});

Using Schema Types in Functions

// convex/products.ts
import { query, mutation } from "./_generated/server";
import { v } from "convex/values";
import { Doc, Id } from "./_generated/dataModel";

// Use Doc type for full documents
type Product = Doc<"products">;

// Use Id type for references
type ProductId = Id<"products">;

export const get = query({
  args: { productId: v.id("products") },
  returns: v.union(
    v.object({
      _id: v.id("products"),
      _creationTime: v.number(),
      name: v.string(),
      description: v.string(),
      price: v.number(),
      category: v.string(),
      inventory: v.number(),
      isActive: v.boolean(),
    }),
    v.null()
  ),
  handler: async (ctx, args): Promise<Product | null> => {
    return await ctx.db.get(args.productId);
  },
});

Best Practices

Never run npx convex deploy unless explicitly instructed
Never run any git commands unless explicitly instructed
Always define explicit schemas rather than relying on inference
Use descriptive index names that include all indexed fields
Start with optional fields when adding new columns
Use discriminated unions for polymorphic data
Validate data at the schema level, not just in functions
Plan index strategy based on query patterns

Common Pitfalls

Missing indexes for queries - Every withIndex needs a corresponding schema index
Wrong index field order - Fields must be queried in order defined
Using v.any() excessively - Lose type safety benefits
Not making new fields optional - Breaks existing data
Forgetting system fields - _id and _creationTime are automatic

References

Convex Documentation: https://docs.convex.dev/
Convex LLMs.txt: https://docs.convex.dev/llms.txt
Schemas: https://docs.convex.dev/database/schemas
Indexes: https://docs.convex.dev/database/indexes
Data Types: https://docs.convex.dev/database/types

Agent Skills: Convex Schema Validator

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