Join in PostgreSQL
Join implementations are under: src/backend/executor
PostgreSQL suports three kinds of join:
- nested loop join (
nodeNestloop.c)
- sort-merge join (
nodeMergejoin.c)
- hash join (
nodeHashjoin.c) (hybrid hash join)
Query optimiser chooses appropriate join, by considering
- physical characteristics of tables being joined
- estimated selectivity (likely number of result tuples)
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