Nested Loop
Short Description
For each row in the outer table, Nested Loop will scan the inner table for matches. This can lead to poor performance.
Detailed Description​
For each row in the outer table, Nested Loop will scan the inner table for matches. This can lead to poor performance as scanning a large inner table can impose a huge I/O load on the server. Targeting indexed columns on the inner table can speed things up by reducing the I/O load.
Additional Links​
- PostgreSQL Documentation - Using Explain
- pgAnalyze - Explain
- eTutorials - Understanding How PostgreSQL Executes a Query
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