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XDEL

Introduction​

In Dragonfly, as well as in Redis and Valkey, the XDEL command is used to delete one or more entries from a stream. This command is particularly useful for managing data in stream-like structures by removing irrelevant or processed items.

Syntax​

XDEL key ID [ID ...]
  • Time complexity: O(1) for each single item to delete in the stream, regardless of the stream size.
  • ACL categories: @write, @stream, @fast

Parameter Explanations​

  • key: The key of the stream from which entries are to be deleted.
  • ID: One or more entry IDs identifying the entries you wish to delete from the stream.

Return Values​

  • The command returns an integer representing the number of entries that were successfully deleted from the stream.

Code Examples​

Basic Example​

Delete a single entry from a stream:

dragonfly$> XADD mystream * name "Alice" age "30"
"1527845627383-0"

dragonfly$> XADD mystream * name "Bob" age "25"
"1527845627383-1"

dragonfly$> XDEL mystream "1527845627383-0"
(integer) 1

dragonfly$> XRANGE mystream - +
1) "1527845627383-1"
   1) "name"
   2) "Bob"
   3) "age"
   4) "25"

Delete Multiple Entries​

Delete multiple entries from the stream by specifying multiple IDs:

dragonfly$> XADD mystream * name "Alice" age "30"
"1527845627383-0"

dragonfly$> XADD mystream * name "Bob" age "25"
"1527845627383-1"

dragonfly$> XADD mystream * name "Charlie" age "22"
"1527845627383-2"

dragonfly$> XADD mystream * name "Diana" age "28"
"1527845627383-3"

dragonfly$> XDEL mystream "1527845627383-1" "1527845627383-3"
(integer) 2

dragonfly$> XRANGE mystream - +
1) 1) "1527845627383-0"
   2) 1) "name"
      2) "Alice"
      3) "age"
      4) "30"
2) 1) "1527845627383-2"
   2) 1) "name"
      2) "Charlie"
      3) "age"
      4) "22"

Best Practices​

  • Make smart use of XDEL to keep your streams tidy and free from outdated or unnecessary data.
  • Consider removing processed entries to prevent the stream from growing indefinitely, which could lead to performance degradation and increased memory usage.

Common Mistakes​

  • Attempting to delete an entry using a non-existent ID, which will result in a deletion count of 0.
  • Assuming XDEL modifies the order of entries in a stream, while it merely removes specific entries and maintains the order of remaining entries.

FAQs​

What happens if the specified IDs do not exist in the stream?​

If the specified IDs do not exist, XDEL will return 0 for each non-existent ID, meaning no entries were deleted.

Can I use XDEL on a non-stream data type?​

No, using XDEL on a non-stream data type will result in an error.