Free Indexes, queries and scale lessonsIndexes, queries and scale · Stage 2 · Executing queries · Step 1
Query plans and join algorithms
Read a plan as a tree of operators, and compare nested-loop, block nested-loop and hash joins by their page cost. About 15 minutes.
Two large tables with no useful index are joined on an equality condition. Which method is usually cheapest?
- AHash join
- BPage nested loop
- CIndex nested loop
Show the answer
Hash join. Cost grows with the sum of the sizes, not their product.
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