title: interpretation of an execution plan with limit and order by
body: <p>I have a test1 table which contains 20'000'000 tuples. I make a request on this table with the order by clause. The number of returned tuples is limited to 10.
  I do not understand why in the execution plan there are less than 20'000'000 of tuples treated whereas with order by clause it should parse the whole table.</p>
  
  <pre><code>demo=# explain select content from test1 order by content limit 10;
   Limit  (cost=451329.69..451330.85 rows=10 width=33)
     -&gt;  Gather Merge  (cost=451329.69..2395909.82 rows=16666666 width=33)
           Workers Planned: 2
           -&gt;  Sort  (cost=450329.66..471163.00 rows=8333333 width=33)
                 Sort Key: content
                 -&gt;  Parallel Seq Scan on test1  (cost=0.00..270249.33 rows=8333333 width=33)
   JIT:
     Functions: 3
     Options: Inlining false, Optimization false, Expressions true, Deforming true
  (9 rows)
  </code></pre>