How deeply does ScyllaDB in Action cover N + 1 query problem?

Defines the pattern and works through a ten-summary example, then stops at schema-level denormalization.

N + 1 query problem

The N+1 problem is a performance problem in which loading a collection and related data requires one initial query plus a separate query for each item.

The N + 1 problem occurs when loading a collection requires one initial query plus a separate query for each related item. Loading 10 article summaries and then fetching each author can therefore require up to 11 database calls. section 5.1.2

Article summaries and authors

Reusing an articles table for summaries would retain each author’s ID. Loading summaries would then require one call for the articles and one author lookup per article. A separate article-summaries table avoids this pattern by storing the author’s name with each summary, alongside the fields needed for the summary view. section 5.1.2

Table 5.1 Article summaries have the same values for some fields, but other fields have subtle differences.

Articles	Article summaries
Title	Title
Author ID	Author name
Score	Score
Gallery of images	One image

Compare the fields used by full articles and article summaries to see why the summary table stores an author name rather than an author ID. section 5.1.2

How ScyllaDB in Action covers it

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Also explained in

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Kubernetes for DevelopersThe N+1 query problem is a database access pattern in which one query retrieves a collection and additional queries retrieve related data for each item.
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Java Persistence with Spring Data and Hibernate epubThe n+1 selects problem is a data-access performance anti-pattern in which one query retrieves a root object and an additional query retrieves each associated object or collection element.
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Troubleshooting Java, Second EditionThe N + 1 query problem is an access pattern in which one initial query is followed by a separate query for each of N retrieved records.

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Related concepts

lazy initializationproduced by · Lazy initialization is a technique that postpones creating, retrieving, computing, or loading a value or resource until it is needed.
eager loadingaddressed by · Eager loading is a data-loading strategy that retrieves required data before it is requested individually, often fetching related data together with its primary entity.
batchingaddressed by · Batching is the grouping of multiple data items, requests, or operations so they can be processed together as a unit.
object-relational mapperproduced by · An object-relational mapper is software that maps programming-language objects and operations to relational database structures and operations.

This explainer was generated by Manning's knowledge graph from the text of ScyllaDB in Action. The section links point to the parts of the book it draws on.