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EXPLAIN Examples (cont)

Example: Select on non-indexed attribute

uni=# explain
uni=# select * from Students where stype='local';
                     QUERY PLAN
----------------------------------------------------
 Seq Scan on students
             (cost=0.00..562.01 rows=23544 width=9)
   Filter: ((stype)::text = 'local'::text)

where

  • Seq Scan = operation (plan node)
  • cost=StartUpCost..TotalCost
  • rows=NumberOfResultTuples
  • width=SizeOfTuple (# bytes)