Software⏱️ 2 min read📅 2026-06-03

How to Fix: Postgres: "ERROR: cached plan must not change result type"

PostgreSQL error: cached plan must not change result type

Quick Answer: The error occurs when the query plan is cached and its result type changes, causing a mismatch. Try rewriting the query to avoid caching or use EXPLAIN ANALYZE to analyze the query execution plan.

📋 Table of Contents

  1. 🛑 Root Causes of the Error
  2. 🚀 How to Resolve This Issue
  3. ✨ Wrapping Up

The error 'cached plan must not change result type' in PostgreSQL occurs when the query plan is being cached and then modified, causing a mismatch between the original plan and the new one. This can happen due to various reasons such as updating the table structure, adding or removing columns, or modifying the query itself.

🛑 Root Causes of the Error

  • Modifying the table structure or adding/removing columns.

🚀 How to Resolve This Issue

Method 1: Rebuilding the Index

  1. Step 1: Drop the index on the column used in the query.
  2. Step 2: Rebuild the index using the REINDEX command.

Method 2: Re-running the Query

  1. Step 1: Run the query with the latest schema changes.

✨ Wrapping Up

To prevent this error from occurring in the future, consider using a more robust query optimization method, such as using materialized views or indexes. Regularly reviewing and updating yourdatabase schema can also help identify potential issues before they occur.

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