Collection
A collection is a data structure or abstraction that groups multiple elements for storage, access, traversal, or processing.
Kotlin in Action, 2E
A collection is a container or aggregate that holds multiple elements and supports operations such as membership testing.
- How it is used
- Uses collections as the main domain for concise Kotlin functions and lambda-based data operations.
- How deep it goes
- Explains creation, operations, mutability contracts, Java correspondence, and lazy sequences without detailing implementation internals.
- Examples
- Demonstrates lists, sets, maps, indexed access, map iteration, and copying from a read-only source into a mutable target.
- What you can do after
- Apply it via Kotlin standard-library functions to create, transform, aggregate, inspect, and safely pass collections.
MongoDB 8.0 in Action, Third Edition
A collection is MongoDB's logical container for related documents.
- How it is used
- Organizes BSON documents within a database and provides the unit for collection options and sharding.
- How deep it goes
- Explains creation, inspection, naming, namespaces, and specialized options with shell commands; does not detail collection storage internals.
- Examples
- Uses sample_mflix collection listings, a namespace lookup, and a db.createCollection() time-series command.
- What you can do after
- Operate/configure collections in mongosh by listing them, inspecting their options, and choosing automatic or explicit creation.
Read how MongoDB 8.0 in Action, Third Edition explains collection →
100 Java Mistakes and How to Avoid Them
A collection is an object representing a group of elements managed through Java's collection abstractions.
- How it is used
- Frames collections as Java abstractions whose lookup, null, mutation, and iteration behavior can produce subtle bugs.
- How deep it goes
- Explains concrete failure modes and prevention rules, while deferring complete mutability classification and complex static analysis.
- Examples
- Uses a List passed to generic varargs, null searches after Set.of() migration, and a sanitizer returning emptyList().
- What you can do after
- Diagnose/debug collection bugs involving silent misses, null queries, equality, and unexpected unsupported mutations.
Read how 100 Java Mistakes and How to Avoid Them explains collection →
AI-Powered Search
A collection is a logical search-engine unit that contains a schema and configuration and holds indexed documents for searching and retrieval.
- How it is used
- Provides the schema-and-configuration unit for indexing documents and searching, ranking, and retrieving results.
- How deep it goes
- Defines the unit and works through creation, indexing, and searches, with a specialized Solr configuration example.
- Examples
- Uses a three-document BM25 test, linked outdoor questions and answers, and an entities lookup for query parsing.
- What you can do after
- Operate/configure it by creating a collection, loading documents, and searching selected fields or extracting query entities.
ScyllaDB in Action
A collection type is a ScyllaDB data type that stores multiple related values, such as set elements or map key-value pairs, in a single column value.
- How it is used
- Selects column types for aggregating small related values in a query-first ScyllaDB schema.
- How deep it goes
- Defines LIST, SET, and MAP, then demonstrates declarations and update operations; defers large or unbounded data to separate tables.
- Examples
- Uses a collections table, unique text sets, editable text maps, and an article image gallery modeled as SET<FROZEN<image>>.
- What you can do after
- Apply it via CQL by choosing, declaring, and updating LIST, SET, or MAP columns for bounded related data.
Clojure: The Essential Reference
A Java collection is an object from Java's collection abstractions that stores or organizes multiple values.
- How it is used
- Enables Clojure collection-processing functions to work with supported Java collections and other container types.
- How deep it goes
- Explains `count` and `set` contracts and selected performance differences, without detailing Java collection interfaces.
- Examples
- Uses vector counting, duplicate removal with `set`, and command-line argument checking; provides no concrete Java collection example.
- What you can do after
- Apply it via Clojure’s `count` and `set` to inspect or transform supported collections, including common Java iterable inputs.
Read how Clojure: The Essential Reference explains collection →
The Well-Grounded Rubyist, Fourth Edition
A collection is an object that groups multiple elements and supports operations for examining or traversing those elements.
- How it is used
- Organizes objects for searching, sorting, filtering, traversal, and transformation across Ruby’s core data structures.
- How deep it goes
- Explains major classes, each-based iteration, Enumerable’s contract, filtering results, and Enumerator laziness without exhaustive API coverage.
- Examples
- Uses array traversal, a custom each implementation, conference payment filtering, numeric selection, and lazy slice-map chains.
- What you can do after
- Apply it via each, Enumerable methods, and Enumerator chains to traverse, select, transform, and process grouped objects.
Read how The Well-Grounded Rubyist, Fourth Edition explains collection →
Building Web APIs with ASP.NET Core
A document-database collection is a grouping of related documents that can contain records with flexible schemas.
- How it is used
- Organizes related board-game records and their associated information in a document-oriented database.
- How deep it goes
- Defines collections through storage-model comparison and embedded relationships, without detailing database commands or implementation code.
- Examples
- Uses users, roles, board games, and comments to contrast embedded documents with separately referenced records.
- What you can do after
- Evaluate whether related records fit an embedded collection design or require key-based references across documents.
Read how Building Web APIs with ASP.NET Core explains collection →
AI Agents and Applications
A collection is a Chroma container for documents, embeddings, metadata, and identifiers.
- How it is used
- Uses collections to ingest chunked content and retrieve semantically related documents for RAG-style questions.
- How deep it goes
- Explains creation, ingestion, embeddings, metadata, identifiers, querying, chunk granularity, and persistence, but not storage internals.
- Examples
- Demonstrates Paestum tourism chunks, Cornwall HTML chunks, granular and coarse collections, and multiple UK destination collections.
- What you can do after
- Build it from scratch with Chroma or LangChain, populate it with chunked documents, and run similarity queries against the stored content.
Microsoft Azure in Action
A MongoDB collection is a container that groups related documents for storage and querying.
- How it is used
- Organizes related documents inside a Cosmos DB database and supports scalable storage and querying.
- How deep it goes
- Explains creation, shard keys, partitions, throughput, and key-selection trade-offs without detailing MongoDB query syntax.
- Examples
- Uses an Azure CLI collection command and an Alpaca-Ma-Bags product catalog partitioned by category.
- What you can do after
- Operate collections via Azure CLI by selecting a partition key and configuring request-unit throughput.
Bootstrapping Microservices, Second Edition: With Docker, Kubernetes, GitHub Actions, and Terraform
A MongoDB collection is a group of related documents within a database.
- How it is used
- Uses collections to store application records and supply test data for a video-streaming microservice.
- How deep it goes
- Explains creation, document insertion, driver access, and fixture loading without detailing collection internals.
- Examples
- Demonstrates a videos collection containing video metadata and fixtures written as JSON or JavaScript.
- What you can do after
- Operate collections by creating them, inserting records with Studio 3T, and accessing them through the MongoDB Node.js driver.
The Quick Python Book, Fourth Edition
A collection is a MongoDB container that groups documents within a database.
- How it is used
- Groups MongoDB documents for Python applications that need scalable, distributed storage and flexible schemas.
- How deep it goes
- Explains selection, lazy creation, CRUD operations, generated identifiers, and dropping collections, but not indexing or schema design.
- Examples
- Uses a PyMongo `docs` collection containing Jane’s profile, then demonstrates querying, updating, replacing, deleting, and dropping it.
- What you can do after
- Apply it via PyMongo to create, query, modify, replace, delete, and drop MongoDB collections and their documents.
Read how The Quick Python Book, Fourth Edition explains collection →
F# in Action: A Revised Edition of Get Programming with F#
A collection is a data structure or abstraction that groups multiple elements for traversal and processing.
- How it is used
- Processes application data through traversal, transformation, aggregation, and composable pipelines.
- How deep it goes
- Explains collection categories, pipeline patterns, aggregation inputs, and safe searches without detailing collection implementation internals.
- Examples
- Uses customer orders, customer debt, shopping baskets, optional values, searches, database results, web services, and event streams.
- What you can do after
- Apply F# collection modules, pipelines, folds, sequences, and safe option-returning operations to process data.
Read how F# in Action: A Revised Edition of Get Programming with F# explains collection →
Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOS
A collection is a container that groups multiple values as a single data object.
- How it is used
- Groups related PowerShell values or objects so commands can inspect, test, or process them together.
- How deep it goes
- Defines collections, demonstrates storage and implicit property enumeration, then briefly applies membership tests and iteration.
- Examples
- Uses computer-name strings, process objects, text files, membership tests, and a number array from one through ten.
- What you can do after
- Apply it via PowerShell by creating collections, reading shared properties, testing membership, and iterating through items.
Learn PowerShell Scripting in a Month of Lunches, Second Edition: Write and organize scripts and tools
A collection is a group of objects treated as a single set of values for operations such as membership testing.
- How it is used
- Supports membership tests and iteration over arrays or other groups of objects in PowerShell scripts.
- How deep it goes
- Explains arrays, membership operators, enumeration, and naming practice through runnable examples, without covering collection internals.
- Examples
- Uses server lists, names read from a file, numeric ranges, and service objects.
- What you can do after
- Apply it via PowerShell to test membership and process each object in turn.
Data Pipelines with Apache Airflow, Second Edition
A collection is a named group of related objects with defined properties and vectorization settings in Weaviate.
- How it is used
- Configures the vector-database target that a recipe-ingestion pipeline checks before storing embedded content.
- How deep it goes
- Explains naming, properties, data types, vectorizers, existence checks, and schema replacement, but not Weaviate internals.
- Examples
- Uses a recipes collection with UUID identifiers, recipe text, content chunks, and a DockerOperator creation task.
- What you can do after
- Operate/configure a Weaviate collection for recipe ingestion with typed properties, vectorization settings, and repeatable creation checks.
Read how Data Pipelines with Apache Airflow, Second Edition explains collection →
Related concepts
- Mapincludes · A map is an associative data structure that stores key-value pairs and supports retrieving values by key.
- arrayincludes · An array is an indexed, ordered collection of elements arranged in one or more dimensions, with elements accessed by position.
- listincludes · A list is an ordered collection of elements arranged in a sequence.
- setincludes · A set is a collection of unique elements in which membership is determined by whether an element is present, not by duplicate occurrences.
- databasepart of · A database is an organized collection of persistent data managed by software for storage, retrieval, querying, and modification.
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