>> rhaas=# explain select a from generate_series(1,100) a union select a
>> from generate_series(1,100) a;
>> QUERY PLAN
>> --------------------------------------------------------------------------------------
>> HashAggregate (cost=45.00..65.00 rows=2000 width=4)
>> -> Append (cost=0.00..40.00 rows=2000 width=4)
Why in this case the estimated number of rows is 2000? Is it standard
planner behavior?
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