[Solved] In PostgreSQL how can I manipulate multiple subquery execution order?

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 t2_idx_cust_id ON "t2" ("cust_id");
CREATE INDEX t3_idx_cust_id_reg_date ON "t3" ("cust_id","reg_date");
The optimized query:
SELECT
        count(*) 
    FROM
        t1 a 
    WHERE
        EXISTS (
            SELECT
                1 
            FROM
                t2 c 
            WHERE
                a.cust_id = c.cust_id OFFSET 0
        ) 
        AND EXISTS (
            SELECT
                1 
            FROM
                t3 b 
            WHERE
                b.reg_date >= '2021-02-02' 
                AND a.cust_id = b.cust_id OFFSET 0
        )

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* original question posted on StackOverflow here.