Re: Experimental evaluation of PostgreSQL's query optimizer

 

For that data, yes. But you're ignoring other important cases. Small or even 1-element lookup tables can be one where a nestloop over a seqscan turns out to be by far the fastest way to do the job. This can really add up if it's deep in a subplan that's excuted repeatedly, or if it's part of queries that get run very frequently on a busy OLTP system.

That said, these cases are also the ones that land up hurting very badly if the stats are inaccurate or outdated and our expected 3 loops turns into 3000.