[Solved] If effective_cache_size is set too low, what is the likely effect on query planning? — Ans: The planner may underestimate available cache and choose less efficient query... | PostgreSQL

PostgreSQL - Performance Tuning

If effective_cache_size is set too low, what is the likely effect on query planning?

AThe planner will overestimate memory and cause out-of-memory errors

BThe planner may underestimate available cache and choose less efficient query plans

CThe database will allocate more memory than available causing slowdowns

DNo effect on query planning, only affects disk caching

Step-by-Step Solution

Solution:

Step 1: Understand planner's use of effective_cache_size
The planner uses this to estimate how much data might be cached in memory.
Step 2: Effect of setting it too low
If too low, planner assumes less cache, may avoid index scans or joins, picking slower plans.
Final Answer:
The planner may underestimate available cache and choose less efficient query plans -> Option B
Quick Check:
Low effective_cache_size = conservative planner estimates [OK]

Quick Trick: Low effective_cache_size makes planner cautious, picks slower plans [OK]

Common Mistakes:

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If effective_cache_size is set too low, what is the likely effect on query planning?