Need

When investigating performance, an Explain Plan is a useful tool to understand what steps are costing the most and therefore impacting performance the most. This article describes how to obtain an Explain Plan with PostgreSQL. 


Summarized Solution

The EXPLAIN command in PostgreSQL is a powerful tool for understanding how the query planner and executor work. It provides insight into query execution strategies, helping identify performance issues such as sequential scans, unnecessary sorts, or inefficient joins.


Detailed Solution


Basic Usage:

You can start with a simple EXPLAIN to see the query plan:

EXPLAIN <your complicated select, insert, update, delete or merge statement>;

⚠️ This does not execute the query, it only shows the planner's estimate.

For accurate performance diagnostics and to communicate with support / professional services, you need more detail.


Recommended Usage:

Use ANALYZE, BUFFERS, TIMING.

EXPLAIN (ANALYZE, BUFFERS, TIMING) <your complicated select, insert, update, delete or merge statement>;

Parameter Breakdown:

  • ANALYZE:
    • Executes the query and shows actual row counts and execution times.
    • Essential to compare planner estimates vs. reality.
  • BUFFERS:
    • Displays buffer usage (shared/local/temp).
    • Helps diagnose I/O pressure and memory efficiency.
  • TIMING:
    • Shows how much time each node takes.
    • Shows how parsing and actual execution contribute to overall execution time.


Why Use All Three Parameters?


ParameterWhy It Matters
ANALYZESee real execution stats, not just estimates.
BUFFERSUnderstand memory vs disk usage and caching behavior.
TIMINGIdentify which parts of the query are slow.


Using all three provides visibility into:

  • Planner accuracy ( you may have insufficient / bad statistics).
  • I/O vs CPU bottlenecks.
  • Index or join strategy effectiveness.


How to share an EXPLAIN Plan?

  • Always share the raw output of the EXPLAIN command (screenshots are not easily readable and will only slow down the analysis process.
  • Don’t use the EXPLAIN button available in DBeaver or your favorite SQL client.
  • Use a tool such as New Explain (EXPLAIN visualizer, provides a shareable URL, and lets you add the query text and comments if need be).