PostgreSQL Hypopg: Virtual Indexes for Query Optimization

Introduction​
Hypopg is a PostgreSQL extension that introduces ​hypothetical indexes​ (or virtual indexes), allowing users to assess the impact of potential indexes on query performance without incurring resource costs. This tool is invaluable for optimizing databases efficiently.

Key Features

• ​Zero Resource Consumption: Virtual indexes are created in memory and do not occupy disk space or CPU.
• ​Seamless Integration: Works with existing PostgreSQL workflows, visible only during EXPLAIN statements.
• ​Multi-Index Support: Compatible with B-tree, BRIN, Hash (PostgreSQL 10+), and Bloom indexes (with the Bloom extension).

Use Cases

• Validate if a proposed index improves query speed.
• Test multiple indexing strategies risk-free.
• Avoid unnecessary physical index creation, reducing storage overhead.

Getting Started

1. ​Install the Extension:

CREATE EXTENSION hypopg;  

‍

2. Create a Virtual Index:

-- Example: Add a virtual index on the "id" column  
SELECT * FROM hypopg_create_index('CREATE INDEX ON hypo (id)');  

‍

3. Verify in EXPLAIN:

-- Check if the optimizer uses the virtual index  
EXPLAIN SELECT val FROM hypo WHERE id = 1;  

‍

Advanced Operations

List Indexes

SELECT * FROM hypopg_list_indexes;  

‍

Hide/Unhide Indexes

SELECT hypopg_hide_index('hypo_id_val_idx'::regclass);  

‍

Reset All Indexes

SELECT hypopg_reset();  

‍

Technical Details

• ​Implementation: Uses PostgreSQL hooks to inject hypothetical indexes into the query planner during the EXPLAIN phase.
• ​Statistics: Estimates index size and selectivity based on table statistics to mimic real-world behavior.

Benefits Over Physical Indexes

• ​Speed: Create and test indexes instantly, even on large tables.
• ​Safety: No impact on production systems or concurrent connections.
• ​Cost Efficiency: Eliminates resource waste from unused physical indexes.

​Conclusion​
Hypopg empowers developers to make informed indexing decisions with minimal overhead. Whether optimizing OLTP workloads or analytical queries, this tool streamlines performance tuning while maintaining system stability. Try it today to unlock smarter database optimization

‍