XADD for adding entries in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command XADD do?

XADD adds a new entry to a Redis stream. It appends data with a unique ID to the stream.

beginner

What is the purpose of the * symbol in XADD mystream *?

The * tells Redis to auto-generate a unique ID for the new stream entry based on the current time.

beginner

How do you specify the fields and values when using XADD?

After the stream name and ID, you list pairs of field names and their values, like field1 value1 field2 value2.

intermediate

What happens if you use XADD mystream 12345-0 field1 value1 and the ID already exists?

Redis will return an error because stream entry IDs must be unique and cannot be reused.

intermediate

How can you limit the length of a Redis stream when adding entries with XADD?

You can use the MAXLEN option to trim the stream to a certain length, for example: XADD mystream MAXLEN 1000 * field value.

What does the XADD command do in Redis?

A Adds a new entry to a stream

B Deletes a stream

C Reads entries from a stream

D Creates a new database

XADD adds new entries to Redis streams.

In XADD mystream *, what does the asterisk * mean?

A Auto-generate an entry ID

B Delete all entries

C Add multiple entries

D Use a fixed ID

The * tells Redis to create a unique ID automatically.

Which of these is a valid way to add fields with XADD?

A XADD mystream * field1 field2 value1 value2

B XADD mystream * value1 field1 value2 field2

C XADD mystream *

D XADD mystream * field1 value1 field2 value2

Fields and values must be paired: field1 value1 field2 value2.

What happens if you try to add an entry with an existing ID using XADD?

A Entry is overwritten

B Redis returns an error

C Entry is ignored

D Stream is deleted

Entry IDs must be unique; Redis returns an error if duplicated.

How do you limit the length of a stream when adding entries?

A Use <code>TRIM</code> command separately

B Use <code>LIMIT</code> option

C Use <code>MAXLEN</code> option

D Use <code>DELETE</code> command

MAXLEN trims the stream to a max length during XADD.

Explain how to add a new entry to a Redis stream using XADD.

Think about the order of arguments and how Redis generates IDs.

Describe how to keep a Redis stream from growing too large when adding entries.

Consider how to limit stream size during XADD.