computer science

Wide-column store

Wide-column store is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Wide-column store rather than just read about it. In short: A wide-column store (or extensible record store) is a type of NoSQL database. It uses tables, rows, and columns, but unlike a relational database, the names and format of the columns can vary from row to row in the same table.

Key takeaways

Wide-column store belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Wide-column store to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Wide-column store from memory before moving on to harder problems.

Reference excerpt

A wide-column store (or extensible record store) is a type of NoSQL database. It uses tables, rows, and columns, but unlike a relational database, the names and format of the columns can vary from row to row in the same table. A wide-column store can be interpreted as a two-dimensional key–value store. Google's Bigtable is one of the prototypical examples of a wide-column store.

Definition The name column-store historicaly referred to databases like C-Store, which was a column-oriented relational database. It eventually came to refer to Bigtable, Apache Cassandra, and similar systems, which also store groups of columns ("column families") together, but ditch the relational model. A wide-column store is a 2-level structure where each value is identified by 2 keys: the first key acts as a row identifier and the second acts as a column identifier. Columns are grouped together into column-families, which are physically stored together on disk. The top-level structure of a wide-column store is called a keyspace, and column families are contained within this structure. A wide-column database may also have supercolumns, which contain a map to other columns, this creating a nest column. The column families of a row may not necessarily be stored together on disk, but the columns within a column family are stored together. A row is made up of a set of keys and values, which may span several column families, a column family is often likened to a table in a relational database.

Versus document databases Compared to a document databases, wide-column databases divide each record into column families that the database recognizes as separate units. This additional structure allows the database to organize into a two-dimensional structure, whereas document databases generally treat the entire document as the unit of storage and optimization despite allowing queries and partial retrievals of individual fields.

Versus relational databases Besides being denormalized, a wide-column database's structure is not as fixed as relational database, allowing dynamically adding columns, as well as allowing rows to have varying columns.

Notable examples Notable wide-column stores include:

Apache Accumulo Apache Cassandra Apache HBase Bigtable DataStax Enterprise (uses Apache Cassandra) DataStax Astra DB (uses Apache Cassandra) Hypertable Azure Tables ScyllaDB

References

Worked examples

Example 1 — a first encounter with Wide-column store

Start with the simplest possible case. Write down what Wide-column store claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Wide-column store before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Wide-column store ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Wide-column store

In research: Wide-column store appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Wide-column store in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Wide-column store is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computing stubs, Database management systems, Databases, so understanding it makes those chapters shorter.
In everyday life: Look for Wide-column store outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Wide-column store” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Wide-column store in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Wide-column store means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Wide-column store out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Wide-column store in simple terms?

Why does Wide-column store matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Wide-column store?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Wide-column store.