cursor-plugin-convex-rule-query-optimization

name	cursor-plugin-convex-rule-query-optimization
description	Use indexes instead of filter() for efficient database queries
metadata	{"version":"0.1.0"}

Query Optimization

Avoid using .filter() on database queries. Instead, use indexed queries with .withIndex() or filter in TypeScript after collecting results.

Why

Using .filter() on queries performs a full table scan, which becomes slow as your data grows. Indexes provide fast lookups.

Examples

Bad:

const user = await ctx.db
  .query("users")
  .filter(q => q.eq(q.field("email"), email))
  .first();

Good:

// In schema.ts
export default defineSchema({
  users: defineTable({
    email: v.string(),
    name: v.string(),
  }).index("by_email", ["email"]),
});

// In your function
const user = await ctx.db
  .query("users")
  .withIndex("by_email", q => q.eq("email", email))
  .first();

For Small Result Sets

If you must filter by a field that doesn't warrant an index:

const allUsers = await ctx.db.query("users").collect();
const filtered = allUsers.filter(user => user.age > 18);