Drizzle ORM – TypeError: undefined is not an object (evaluating ‘relation.referencedTable’)

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Summary

A TypeError occurs when executing a relational query in Drizzle ORM (relation.referencedTable is undefined). This happens because the defineRelations configuration expects specific table names (workspaceMembers, workspaces, users) as keys, but the imported schema object uses a different key (workspaceMembers vs workspaceMember). Consequently, Drizzle fails to resolve the references during query building. The fix is to ensure the keys in the schema object match the keys expected by the relations object exactly.

Root Cause

The root cause is a schema key mismatch between the schema import and the relations definition.

  1. Schema Import: The code imports the schema via export * from "./schema/workspaceMember". If the workspaceMember.ts file exports the table as workspaceMembers, and the tables.ts file re-exports it, the resulting schema object likely has the key workspaceMembers.
  2. Relations Definition: The defineRelations function is called with { users, workspaces, workspaceMembers }. This acts as a registry.
  3. The Conflict: When the drizzle instance is initialized, it receives both schema and relations. Drizzle attempts to link them.
    • Inside workspaceMemberRelations, the code references r.one.workspaces(...). This implies r needs to know about a table named workspaces.
    • The stack trace indicates the failure happens inside normalizeRelation. This function is trying to resolve the referencedTable defined in the relation.
    • Because the keys in the provided objects do not align (e.g., schema might be indexed under workspaceMember while relations looks for workspaceMembers), the internal map used to resolve these references contains undefined values.

Why This Happens in Real Systems

In real-world systems, this issue typically arises due to inconsistent naming conventions across the data access layer.

  • Singular vs. Plural: Developers often use singular names for files (e.g., user.ts) but plural names for table instances (e.g., export const users = ...).
  • Aggregated Index Files: When using an index.ts file to aggregate all schemas (export * from ...), the resulting object keys depend entirely on how the exports are named in the source files.
  • Runtime vs. Build Time: TypeScript interfaces might pass validation because types are structural, but the drizzle function relies on runtime object keys. If the runtime object structure doesn’t match the defineRelations configuration, it fails at execution time.

Real-World Impact

  • Runtime Crash: The application crashes immediately when the specific database query is executed, causing an unhandled promise rejection or server crash.
  • Blocked Feature Development: Feature work depending on relational queries (like checking workspace membership) is halted.
  • Opaque Error Messages: Drizzle ORM errors can sometimes be cryptic, pointing to internal library code rather than the specific schema mismatch, leading to wasted debugging time.

Example or Code

The initialization of the Drizzle instance requires the schema object keys to strictly match the keys provided to defineRelations.

import { drizzle } from "drizzle-orm/cockroach";
import * as schema from "../database/tables";
import * as relations from "../database/relations";

// CRITICAL: 'schema' keys must match 'relations' registry keys.
// If 'tables.ts' exports 'workspaceMembers' (plural), 
// 'defineRelations' must receive an object with that exact key.
drizzleInstance = drizzle({
  client: pool,
  schema: {
    ...schema,
    // Sometimes a manual override is needed if exports are inconsistent
    workspaceMembers: schema.workspaceMembers, 
    workspaces: schema.workspaces,
    users: schema.users
  },
  relations
});

How Senior Engineers Fix It

Senior engineers approach this by enforcing strict consistency and defensive initialization.

  1. Normalize Naming: Standardize on a singular or plural convention for both file names and export names (e.g., always export table instances as plural: users, workspaces).
  2. Explicit Object Mapping: Instead of using import * as schema, explicitly construct the schema object passed to Drizzle. This prevents hidden key mismatches caused by wildcards. 
    // Better approach
const db = drizzle({
  schema: {
    users,
    workspaces,
    workspaceMembers
  },
  relations: {
    userRelations,
    workspaceRelations,
    workspaceMemberRelations
  }
});
  3. Verification: Add a “smoke test” for the database connection that performs a simple relational query on startup. This catches configuration errors immediately, rather than during a user request.

Why Juniors Miss It

Juniors often struggle to spot this because:

  • IntelliSense Assumption: They rely on IDE autocomplete which often normalizes imports or suggests the “correct” type without verifying the actual runtime object keys.
  • Focus on Syntax: They focus on the syntax of the defineRelations function (the logic of r.one) rather than the data structure being passed into it.
  • Lack of Runtime Inspection: They don’t inspect the actual content of the schema variable (e.g., console.log(Object.keys(schema))) to confirm what keys are available at runtime versus what defineRelations expects.
  • Type Safety False Sense of Security: TypeScript might infer the types correctly based on loose structural matching, masking the fact that the specific object keys Drizzle ORM needs internally are wrong.