XTRIM

Syntax

XTRIM key <MAXLEN | MINID> [= | ~] threshold [LIMIT count]

Time Complexity: O(N), with N being the number of evicted entries. Constant times are very small however, since entries are organized in macro nodes containing multiple entries that can be released with a single deallocation.

ACL categories: @write, @stream, @slow

XTRIM works same like how trimming works in XADD (when option specified). But instead of adding a new entry, XTRIM focuses completely on trimming entries. <key> is the stream name of which the entries need to be trimmed.

With XTRIM, you can either specify MAXLEN or MINID to control the stratgy to trim.

MAXLEN ensures that the number of entries in a stream doesn't exceed a certain limit. MINID on the other hand ensures that entries with IDs less than the specified MINID get deleted. These two options take a threshold denoting the length (in case of MAXLEN) or ID (in case of MINID).

Dragonfly gives two options to control the trimming nature. "=" argument tells the command to do the exact trimming of entries. Whereas ~ argument tells the command to do the approximate trimming. That is, it is upto the command to decide how many entries need to be deleted. So a stream may have few more entries than the given threshold (due to performance reasons). It is more efficient than exact trimming. By default, exact trimming is used when no options are specified.

dragonfly> XTRIM mystream MAXLEN ~ 100
(integer) 98

LIMIT is useful when you want to limit the number of delete operations used for MAXLEN or MINID (in case of approximate trimming). When LIMIT isn't specified, the default value of 100 * the number of entries in a macro node will be implicitly used as the count. Specifying the value 0 as count disables the limiting mechanism entirely.

dragonfly> XTRIM mystream MAXLEN ~ 100 LIMIT 2
(integer) 2

Return

Integer reply: The number of entries deleted from the stream.

Example

dragonfly> XADD mystream * name John
"1687921762755-0"
dragonfly> XADD mystream * name Alice
"1687924580856-0"
dragonfly> XADD mystream * name Bob
"1687924609465-0"
dragonfly> XLEN mystream
(integer) 3
dragonfly> XTRIM mystream MAXLEN = 2
(integer) 2