How deeply does ScyllaDB in Action cover now?

Explains identifier construction, timestamp ordering, insertion syntax, and the consequence of not knowing generated keys immediately.

Now

As explained in ScyllaDB in Action

The now() function is a ScyllaDB function that generates a TIMEUUID from the current time and the hardware MAC address.

now() generates a TIMEUUID from the current time and the hardware MAC address. Because TIMEUUID values encode timestamps, they can order records by creation time. section 4.4.1

Use now() when inserting a row whose primary key is a TIMEUUID. It avoids manually creating the identifier, but the application cannot know the generated key until it reads the row. section 4.4.1 section 6.1.1

Insert an author

An authors table can use a TIMEUUID primary key. Insert an author with `INSERT INTO authors(id, name) VALUES (now(), 'Alice Author');`. If the generated ID must be reused immediately, generate the TIMEUUID externally instead. section 6.1.1

cqlsh: types> INSERT INTO basic(text, uuid, timeuuid)
  VALUES ('uuids', uuid(), now());

Try now() alongside uuid() in cqlsh to compare a random UUID with a time-based UUID. section 4.4.1

ScyllaDB can convert the resulting TIMEUUID back into a readable timestamp with toTimestamp(timeuuid), making the encoded time visible in query results. section 4.4.1

How ScyllaDB in Action covers it

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Related concepts

timestampequivalent to · A timestamp is a value representing a specific point in time, typically associated with an event, observation, or data item.
clockused by · A computer clock is a timekeeping source or interface that provides time values or measurements to software.
database functionkind of · A database function is a named routine stored or executed in a database that accepts inputs and computes a result, often a scalar or table-valued result.
system_clockused by · std::chrono::system_clock is a C++ standard-library clock that represents system-wide wall-clock time and can be converted to and from calendar time.
timeuuidproduces · A TIMEUUID is a UUID type that encodes a timestamp, allowing identifiers to be ordered by generation time while retaining uniqueness.

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.