EXPLAIN vs EXPLAIN ANALYZE?
Understand the concept
EXPLAIN shows the execution plan the database expects to use. EXPLAIN ANALYZE actually executes the statement and adds observed rows and timing, which helps reveal bad estimates or expensive steps. Since it runs the statement, write queries and expensive reads need appropriate care.
Important ideas
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EXPLAIN shows the planned execution steps and estimates.
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EXPLAIN ANALYZE executes the query and adds actual timings and row counts.
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Use care with writes: analysis executes them too; prefer a safe test database.
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Compare estimated and actual rows at each step, and use buffer information when investigating I/O costs.
Can you explain it without the notes?
EXPLAIN vs EXPLAIN ANALYZE?
Use your own words. Explain an example and one limitation before checking the explanation.
Check your explanation
EXPLAIN shows the execution plan the database expects to use. EXPLAIN ANALYZE actually executes the statement and adds observed rows and timing, which helps reveal bad estimates or expensive steps. Since it runs the statement, write queries and expensive reads need appropriate care.
Turn this concept into a clear answer.
- A large estimation error can explain a poor join choice; adding an index is not the only possible fix.
Keep connecting the ideas.
Next lesson: Is an index scan always faster than a sequential scan?Adapted from 05_SQL_POSTGRESQL.md · “EXPLAIN vs EXPLAIN ANALYZE?”. Examples are study fragments; framework behavior can depend on your version.