Vol. I · A Postgres HandbookTwelve chapters · · 756 queries

The Query & the Schema

A reading-room reference for writing PostgreSQL by hand — selects to window functions, with the schema in plain view.

AdvancedPerformance & Indexes

Create an Expression (Function-based) Index

SQL

CREATE INDEX idx_emp_email_lower 
ON employees (LOWER(email));

Tested against PostgreSQL 16

Note

“Optimizes queries that use functions in the WHERE clause, e.g., WHERE LOWER(email) = \'test@test.com\' .