Given work_mem = '4MB' and a query performing 5 simultaneous sorts, what is the maximum total memory PostgreSQL might use for these sorts?

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PostgreSQL - Performance Tuning

Given work_mem = '4MB' and a query performing 5 simultaneous sorts, what is the maximum total memory PostgreSQL might use for these sorts?

A4MB

B5MB

C20MB

D9MB

Step-by-Step Solution

Solution:

Step 1: Calculate total memory for sorts
Each sort can use up to 4MB, so 5 sorts use 5 x 4MB = 20MB.
Step 2: Confirm no shared memory pooling
Memory is allocated per operation, so total is sum of all.
Final Answer:
20MB -> Option C
Quick Check:
Total memory = work_mem x number of sorts [OK]

Quick Trick: Multiply work_mem by number of simultaneous operations [OK]

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