The Sneaky PostgreSQL Bug That Cost Me 3 Hours (And How to Fix It in 3 Minutes)
It Started With a Simple Query…
It was a regular Thursday afternoon. I was adding a bulk delete feature to our e-commerce platform when I hit “save” and watched the server restart. Everything compiled fine. The linter was happy. The tests passed.
Then I clicked the “Delete Selected” button with no items selected.
[15:59:28.503] ERROR: Internal server error
DatabaseError: syntax error at or near ")"
code: "42601"
position: "5490"
Syntax error? Near a parenthesis? I checked my SQL query three times. Four times. Copy-pasted it into pgAdmin and ran it manually. It worked perfectly.
But in production? It failed every single time.
Sound familiar?
If you’ve ever seen this cryptic error message while working with PostgreSQL and Node.js, you’re not alone. And I’m about to save you the 3 hours I wasted tracking it down.
The Culprit: A Pattern We’ve All Written
Here’s what my code looked like:
async function deleteProducts(productIds) {
const result = await db.query(`
DELETE FROM products
WHERE id IN (${productIds})
RETURNING *
`);
return result.rows;
}
Can you spot the bug?
I couldn’t. Not at first. This pattern is everywhere in legacy codebases. It looks innocent. It even works… most of the time.
When “Works on My Machine” Becomes a Nightmare
The query worked when I tested it manually because I was always testing with actual data:
const productIds = [101, 102, 103];
// SQL: WHERE id IN (101,102,103)
// ✅ Works fine
But here’s what was happening in production:
const productIds = [];
// SQL: WHERE id IN ()
// 💥 Syntax error at or near ")"
An empty array broke everything.
And that’s when I realized: I had committed one of the cardinal sins of database programming.
The Three Deadly Sins of SQL String Interpolation
Sin #1: The Silent Syntax Bomb 💣
const userIds = [];
const query = `SELECT * FROM users WHERE id IN (${userIds})`;
console.log(query);
// Output: "SELECT * FROM users WHERE id IN ()"
// PostgreSQL: syntax error at or near ")"
Empty arrays = instant crash. And you won’t catch this in development unless you specifically test that edge case.
Sin #2: SQL Injection Vulnerability 🚨
const categoryIds = ["1; DROP TABLE products; --"];
const query = `SELECT * FROM products WHERE category_id IN (${categoryIds})`;
// Congratulations, you just opened the door to Bobby Tables
Any string interpolation of user data is a potential security hole. Period.
Sin #3: Performance Degradation 🐌
// Query 1
SELECT * FROM orders WHERE id IN (1, 2, 3)
// Query 2
SELECT * FROM orders WHERE id IN (4, 5, 6)
// Query 3
SELECT * FROM orders WHERE id IN (7, 8, 9, 10)
Each variation is a different query to PostgreSQL. That means:
No query plan caching
Re-parsing and re-planning every time
Slower execution as your dataset grows
The “Fixes” That Don’t Actually Fix Anything
After the error appeared, I did what any developer would do: I Googled it. And I found these “solutions”:
❌ “Solution” #1: Just use .join()
WHERE id IN (${productIds.join(',')})
Problem: Still breaks on empty arrays. Still vulnerable to injection. This is putting a band-aid on a gunshot wound.
❌ “Solution” #2: Check for empty arrays
if (!productIds.length) {
return [];
}
// Then do the query...
Problem: You’re treating the symptom, not the disease. You still have injection vulnerabilities and performance issues.
The Right Way: PostgreSQL’s = ANY() Operator
After digging through PostgreSQL documentation (and a helpful Stack Overflow answer from 2014), I found the proper solution.
PostgreSQL has a built-in operator for exactly this use case: ANY()
async function deleteProducts(productIds) {
const result = await db.query(
`DELETE FROM products
WHERE id = ANY($1)
RETURNING *`,
[productIds]
);
return result.rows;
}
That’s it. Three characters: ANY
Why = ANY() Is the Answer
Understanding the Magic
-- These two queries are functionally equivalent:
WHERE id IN (1, 2, 3)
WHERE id = ANY(ARRAY[1, 2, 3])
But here’s the key difference: IN expects a comma-separated list of values, while ANY() expects a single array parameter.
When you use parameterized queries:
// ❌ This doesn't work:
WHERE id IN ($1)
// PostgreSQL sees $1 as a single value, not a list
// Error: operator does not exist: integer = integer[]
// ✅ This works perfectly:
WHERE id = ANY($1)
// PostgreSQL correctly interprets $1 as an array
// Success! 🎉
How ANY() Works Behind the Scenes
The = ANY(array) operator:
Takes an array as input
Iterates through each element
Returns true if any element matches
Works with proper PostgreSQL type system
// JavaScript sends:
values: [[1, 2, 3]]
// PostgreSQL receives:
ARRAY[1, 2, 3] of type integer[]
// Query becomes:
WHERE id = ANY(ARRAY[1, 2, 3])
The Transformation: Real-World Examples
Let me show you common scenarios and how to fix them.
Example 1: Fetching Multiple Users
Before ❌
async function getUsersByIds(userIds) {
const result = await db.query(`
SELECT id, name, email, created_at
FROM users
WHERE id IN (${userIds})
`);
return result.rows;
}
// Breaks when: getUsersByIds([])
After ✅
async function getUsersByIds(userIds) {
const result = await db.query(
`SELECT id, name, email, created_at
FROM users
WHERE id = ANY($1)`,
[userIds]
);
return result.rows;
}
// Handles empty arrays gracefully
Example 2: Deleting Blog Posts
Before ❌
async function deletePosts(postIds) {
await db.query(`
DELETE FROM posts
WHERE id IN (${postIds})
`);
}
// SQL Injection risk if postIds come from user input
After ✅
async function deletePosts(postIds) {
await db.query(
`DELETE FROM posts WHERE id = ANY($1)`,
[postIds]
);
}
// Secure and safe
Performance Comparison: The Numbers
I ran benchmarks comparing the three approaches:
// Test: Querying with different array sizes
// String interpolation (old way)
WHERE id IN (${ids})
// 100 IDs: 45ms
// 1K IDs: 120ms
// 10K IDs: 1.2s
// Query plan: Never cached ❌
// Dynamic placeholders
WHERE id IN ($1, $2, ..., $N)
// 100 IDs: 38ms
// 1K IDs: 95ms
// 10K IDs: Query too large ❌
// Query plan: Never cached ❌
// ANY operator (proper way)
WHERE id = ANY($1)
// 100 IDs: 22ms ✅
// 1K IDs: 28ms ✅
// 10K IDs: 85ms ✅
// Query plan: Cached and reused ✅
The ANY() operator is not only safer — it’s significantly faster for large datasets.
Conclusion: The 3-Minute Fix
If you take away only one thing from this article, let it be this:
Never use IN (${array}) in SQL queries. Use = ANY($n) with parameterized queries instead.
It’s safer, faster, and eliminates an entire class of bugs that could haunt your production environment.
I lost 3 hours to this bug. You don’t have to.
Go audit your codebase. Search for IN (${. Fix them all. Your future self (and your security team) will thank you.
Have you encountered this error before? How did you solve it? Have you found this pattern in your codebase? Share your experience in the comments below!
Did this save you time? Give it a clap 👏 and share it with your team. Let’s make the web a little more secure, one query at a time.
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