{"id":25799,"date":"2022-06-12T12:10:53","date_gmt":"2022-06-12T02:10:53","guid":{"rendered":"https:\/\/database.guide\/?p=25799"},"modified":"2022-06-14T16:03:02","modified_gmt":"2022-06-14T06:03:02","slug":"redis-set-command-explained","status":"publish","type":"post","link":"https:\/\/database.guide\/redis-set-command-explained\/","title":{"rendered":"Redis SET Command Explained"},"content":{"rendered":"\n

In Redis, the SET<\/code> command sets a key to hold a given string value.<\/p>\n\n\n\n

If the key already holds a value, it is overwritten with the new value. Also, any previous time to live associated with the key is discarded (assuming a successful SET<\/code> operation).<\/p>\n\n\n\n\n\n\n\n

Syntax<\/h2>\n\n\n\n

The syntax goes like this:<\/p>\n\n\n\n

SET key value [ NX | XX] [GET] [ EX seconds | PX milliseconds | EXAT unix-time-seconds | PXAT unix-time-milliseconds | KEEPTTL]<\/code><\/pre>\n\n\n\n
Here’s an explanation of the various options:<\/p>\n\n\n\n
EX<\/code>\u00a0seconds<\/em><\/td>Sets the specified expire time, in seconds.<\/td><\/tr>
PX<\/code>\u00a0millisecond<\/em><\/td>Sets the specified expire time, in milliseconds.<\/td><\/tr>
EXAT<\/code>\u00a0timestamp-second<\/em><\/td>Sets the specified Unix time at which the key will expire, in seconds.<\/td><\/tr>
PXAT<\/code>\u00a0timestamp-milliseconds<\/em><\/td>Sets the specified Unix time at which the key will expire, in milliseconds.<\/td><\/tr>
NX<\/code><\/td>Only sets the key if it does not already exist.<\/td><\/tr>
XX<\/code><\/td>Only sets the key if it already exists.<\/td><\/tr>
KEEPTTL<\/code><\/td>Retains the time to live associated with the key.<\/td><\/tr>
GET<\/code><\/td>Returns the old string stored at the key, or nil if the key did not exist. An error is returned and\u00a0SET<\/code>\u00a0aborted if the value stored at key is not a string.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
See the Redis documentation<\/a> for any changes to the above information.<\/p>\n\n\n\n
Example<\/h2>\n\n\n\n
Here’s a basic example to demonstrate:<\/p>\n\n\n\n
SET type \"Dog\"<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
In this case, the SET<\/code> operation was successful, and so we got a simple string reply of OK<\/code>.<\/p>\n\n\n\n
We can now check the value of the type<\/code> key with the GET<\/a><\/code> command:<\/p>\n\n\n\n
GET type<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"Dog\"<\/pre>\n\n\n\n
The NX<\/code> Option<\/h2>\n\n\n\n
Here’s an example of trying to set another value to the same key when using the NX<\/code> option:<\/p>\n\n\n\n
SET type \"Cat\" NX<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(nil)<\/pre>\n\n\n\n
The NX<\/code> option prevents the key being set if it already exists. In our case, it already exists and so the result is a null reply, or (nil)<\/code>.<\/p>\n\n\n\n
The XX<\/code> Option<\/h2>\n\n\n\n
Here’s an example of using the XX<\/code> option:<\/p>\n\n\n\n
SET type \"Cat\" XX<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
The XX<\/code> option prevents the key being set if it doesn’t<\/em> already exist. In our case, it already exists and so the key is set.<\/p>\n\n\n\n
Here’s what happens if we try to set key that doesn’t already exist:<\/p>\n\n\n\n
SET country \"Thailand\" XX<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(nil)<\/pre>\n\n\n\n
The key wasn’t set, because it doesn’t already exist.<\/p>\n\n\n\n
The GET<\/code> Option<\/h2>\n\n\n\n
Here’s an example of using the GET<\/code> option:<\/p>\n\n\n\n
SET type \"Bird\" GET<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"Cat\"<\/pre>\n\n\n\n
The GET<\/code> option returns the old value of the key. In our case, we had previously set the type<\/code> key to Cat<\/code> and so that’s what is returned. <\/p>\n\n\n\n
Bear in mind that the key now holds the new value:<\/p>\n\n\n\n
GET type<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"Bird\"<\/pre>\n\n\n\n
This option can be used as a replacement for the GETSET<\/code> command (which has been regarded as deprecated since Redis 6.2.0).<\/p>\n\n\n\n
Set an Expiry Time<\/h2>\n\n\n\n
Here’s an example of using the EX<\/code> option to set an expiry time:<\/p>\n\n\n\n
SET type \"Horse\" EX 5<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
The EX<\/code> option allows us to set an expiry time, in seconds. In this case, I set the expiry time to 5 seconds.<\/p>\n\n\n\n
Here’s what happens when I run the GET<\/code> command after waiting for more than 5 seconds:<\/p>\n\n\n\n
GET type<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(nil)<\/pre>\n\n\n\n
So the key no longer exists.<\/p>\n\n\n\n
We can alternatively use the PX<\/code> option to specify the expiry time in milliseconds, or the EXAT<\/code> option to set the Unix time at which the key will expire, in seconds, or PXAT<\/code> for milliseconds.<\/p>\n","protected":false},"excerpt":{"rendered":"
In Redis, the SET command sets a key to hold a given string value. If the key already holds a value, it is overwritten with the new value. Also, any previous time to live associated with the key is discarded (assuming a successful SET operation).<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[153],"tags":[154,84,20],"class_list":["post-25799","post","type-post","status-publish","format-standard","hentry","category-redis","tag-commands","tag-string","tag-what-is"],"_links":{"self":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/25799","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/comments?post=25799"}],"version-history":[{"count":5,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/25799\/revisions"}],"predecessor-version":[{"id":25919,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/25799\/revisions\/25919"}],"wp:attachment":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/media?parent=25799"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/categories?post=25799"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/tags?post=25799"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}