[Solved] Slow query with distinct/group by on varchar column with Postgres

How to optimize this SQL query?

In case you have your own slow SQL query, you can optimize it automatically here.

For the query above, the following recommendations will be helpful as part of the SQL tuning process.
You'll find 3 sections below:

  1. Description of the steps you can take to speed up the query.
  2. The optimal indexes for this query, which you can copy and create in your database.
  3. An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
  1. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
Optimal indexes for this query:
CREATE INDEX company_idx_id ON "company" ("id");
CREATE INDEX company_industry_idx_industry_id ON "company_industry" ("industry_id");
CREATE INDEX industry_idx_id ON "industry" ("id");
The optimized query:
SELECT
        c.city_name AS city 
    FROM
        industry AS i 
    INNER JOIN
        company_industry AS ci 
            ON (
                ci.industry_id = i.id
            ) 
    INNER JOIN
        company AS c 
            ON (
                c.id = ci.company_id
            ) 
    WHERE
        i.id = 288 
    GROUP BY
        city

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* original question posted on StackOverflow here.