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PostgreSQLquery~5 mins

Work_mem and effective_cache_size tuning in PostgreSQL - Cheat Sheet & Quick Revision

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Recall & Review
beginner
What does the work_mem setting control in PostgreSQL?

work_mem controls the amount of memory used for internal sort operations and hash tables before writing to disk. Increasing it can speed up queries that need sorting or hashing.

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beginner
What is the purpose of effective_cache_size in PostgreSQL?

effective_cache_size estimates how much memory is available for disk caching by the operating system and PostgreSQL. It helps the query planner decide if using an index is likely to be fast.

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intermediate
How does increasing work_mem affect query performance?

Increasing work_mem allows larger operations to happen in memory, reducing slow disk writes. But setting it too high can cause memory exhaustion if many queries run simultaneously.

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intermediate
Why should effective_cache_size be set to a value close to available OS cache?

Because it tells PostgreSQL how much data it can expect to find in the OS cache. A realistic value helps the planner choose efficient query plans, like using indexes when data is likely cached.

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advanced
What is a safe approach to tuning work_mem and effective_cache_size?

Start with conservative values, monitor query performance and memory usage, then gradually adjust. For work_mem, consider workload concurrency. For effective_cache_size, estimate OS cache size realistically.

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What does increasing work_mem primarily improve?
ADisk space for storing tables
BSorting and hashing operations in queries
CNetwork bandwidth for connections
DNumber of concurrent connections
What does effective_cache_size represent?
AEstimated memory available for disk caching by OS and PostgreSQL
BSize of the largest table in the database
CMaximum memory PostgreSQL can use for connections
DMemory available for PostgreSQL's internal cache only
What risk comes from setting work_mem too high?
AIndexes will be ignored
BDisk space will run out
CQueries will run slower
DMemory exhaustion if many queries run at once
Why is it important to set effective_cache_size realistically?
ATo avoid PostgreSQL crashing
BTo limit the number of connections
CTo help the query planner choose efficient plans
DTo increase disk space
Which of these is a good first step when tuning work_mem and effective_cache_size?
AStart with conservative values and monitor performance
BDisable caching completely
CSet both to maximum values immediately
DIgnore <code>effective_cache_size</code> and only tune <code>work_mem</code>
Explain what work_mem and effective_cache_size do in PostgreSQL and why tuning them matters.
Think about memory use during query execution and how PostgreSQL plans queries.
You got /4 concepts.
    Describe a safe approach to adjusting work_mem and effective_cache_size for better database performance.
    Focus on careful testing and gradual tuning.
    You got /5 concepts.