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High Performance PostgreSQL for Rails: Data Scan Definition (Chapter 8, page 145)

yagosansz

yagosansz

High Performance PostgreSQL for Rails: Data Scan Definition (Chapter 8, page 145)

Hello @andatki,

On Chapter 8, page 145, in the Generating Data for Experiments section, one of the paragraphs stars with the following: "When does it flip from sequential scans to index scans?..”

I believe this should be "When does it flip from index scans to sequential scans?..” instead.

This makes more sense, since it then goes on to explain that a query that specifies many fields of data, using an index that does not cover all fields may trigger PostgreSQL to resort to a table sequential scan.

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First Post!

andatki

andatki

Author of High Performance PostgreSQL for Rails

Hello @yagosansz. Thanks for taking the time to write this up.

I agree that the order you described makes more sense (index scans to sequential scans), as that’s the type of plan change that would harm performance.

I’ll see if we can get a correction in place and follow up. Thanks again!

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