Introduction to PostgreSQL Indexes ::
dlt.github.io
Who’s this for Basics How data is stored in disk How indexes speedup access to data Costs associated with indexes Disk Space Write operations Query planner Memory usage Types of Indexes Btree Hash BRIN GIN GiST & SP-GiST Conclusion Who’s this for This text is for developers that have an intuitive knowledge of what database indexes are, but don’t necessarily know how they work internaly, what are the tradeoffs associated with indexes, what are the types of indexes provided by postgres and how you can use some of its more advanced options to make them more optimized for your use case.
  • NostraDavid
    2·
    9 天前

    Here’s my quick guide to fixing slow queries:

    1. grab your query.
    2. run EXPLAIN ANALYZE <query>
    3. If there’s a Parallel Seq Scan, check the Filter value (which column are we checking) - you should likely try adding an index.
    4. run CREATE INDEX ON <table>(<column>);
    5. run EXPLAIN ANALYZE <query> again to check for improvements

    Note that EXPLAIN <query> will only do a rough analysis, while EXPLAIN ANALYZE <query> will run your actual query, and analyse it.

    If you want to ANALYSE EXPLAIN an INSERT query, do this:

    BEGIN;
EXPLAIN ANALYZE INSERT ...;
ROLLBACK;

    A simple ROLLBACK will help you here.

    Rewriting the query will typically not do much - it might, but the chance it relatively small vs slapping an index on it.