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To find the node or operator that is consuming the most resource and taking the most time
Partition elimination
Index usage
Nested loop joins
Check what data is being broadcast
Poorly written queries / lack of statistics can lead the optimizer to ship the larger of 2 join tables significantly affecting performance
Identify inflight skew
Look for data spillage
Two ways to get a plan
Explain select … from … where …;
Explain analyze select … from … where …;