{"id":26082,"date":"2022-07-04T13:14:08","date_gmt":"2022-07-04T03:14:08","guid":{"rendered":"https:\/\/database.guide\/?p=26082"},"modified":"2022-07-17T11:54:31","modified_gmt":"2022-07-17T01:54:31","slug":"redis-restore-command-explained","status":"publish","type":"post","link":"https:\/\/database.guide\/redis-restore-command-explained\/","title":{"rendered":"Redis RESTORE Command Explained"},"content":{"rendered":"\n

In Redis, the RESTORE<\/code> command creates a key associated with a value that is obtained by deserialising the provided serialised value (obtained via the DUMP<\/a><\/code> command).<\/p>\n\n\n\n

The serialisation format contains a 64-bit checksum, as well as the RDB version. The RESTORE<\/code> command checks the RDB version and data checksum. If they don’t match an error is returned.<\/p>\n\n\n\n\n\n\n\n

Syntax<\/h2>\n\n\n\n
RESTORE key ttl serialized-value [REPLACE] [ABSTTL] [IDLETIME seconds] [FREQ frequency]<\/code><\/pre>\n\n\n\n
Explanation of the arguments: <\/p>\n\n\n\n
key<\/code><\/td>The key to create and store the deserialised data.<\/td><\/tr>
ttl<\/code><\/td>The time to live. If ttl<\/code> is 0<\/code> the key is created without any expire, otherwise the specified expire time (in milliseconds) is set.<\/td><\/tr>
serialized-value<\/code><\/td>The serialised value to restore.<\/td><\/tr>
[REPLACE]<\/code><\/td>Replaces the key if it already exists. Without this, an error will occur if the key already exists.<\/td><\/tr>
[ABSTTL]<\/code><\/td>When this modifier is used, ttl<\/code> represents an absolute Unix timestamp (in milliseconds) in which the key will expire.<\/td><\/tr>
[IDLETIME seconds]<\/code><\/td>This is the idle time of the key, that is the approximated number of seconds elapsed since the last access to the key. <\/td><\/tr>
[FREQ freqency]<\/code><\/td>The access frequency index of the key. The returned integer is proportional to the logarithm of the recent access frequency of the key. Can be used for eviction purposes.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Example<\/h2>\n\n\n\n
Here’s an example to demonstrate:<\/p>\n\n\n\n
RESTORE type 0 \"\\x00\\x03Dog\\n\\x00\\x14\\x069\\xb24\\x14\\xe4\\xd6\"<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
In this case, I created a key called type<\/code> and restored the serialised value to it. I also set a ttl<\/code> of 0<\/code>, which means that it has no expiry.<\/p>\n\n\n\n
Let’s check the value of our new type<\/code> key:<\/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
When the Key Already Exists<\/h2>\n\n\n\n
By default, if the key already exists, an error is returned. <\/p>\n\n\n\n
To demonstrate this let’s run the previous code again (but with a slightly different serialised value):<\/p>\n\n\n\n
RESTORE type 0 \"\\x00\\x03Cat\\n\\x00\\x10\\x1e\\xeaH\\xafMl\\x17\"<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(error) BUSYKEY Target key name already exists.<\/pre>\n\n\n\n
As expected, we got an error.<\/p>\n\n\n\n
The REPLACE<\/code> Argument<\/h2>\n\n\n\n
We can use the REPLACE<\/code> argument to replace the key if it already exists.<\/p>\n\n\n\n
Let’s try running the previous code again, but this time we’ll add the REPLACE<\/code> argument:<\/p>\n\n\n\n
RESTORE type 0 \"\\x00\\x03Cat\\n\\x00\\x10\\x1e\\xeaH\\xafMl\\x17\" REPLACE<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
This time the operation succeeded without error.<\/p>\n\n\n\n
Let’s check the key’s value:<\/p>\n\n\n\n
GET type<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"Cat\"<\/pre>\n\n\n\n
So we can see that the new deserialised value has been assigned to the key. <\/p>\n\n\n\n
Set an Expiry Time<\/h2>\n\n\n\n
The previous examples set a ttl<\/code> of 0<\/code>, which means that the key has no expiry. We can use a value other than 0<\/code> to set an expire time, in milliseconds, for the key:<\/p>\n\n\n\n
RESTORE type 60000 \"\\x00\\x03Cat\\n\\x00\\x10\\x1e\\xeaH\\xafMl\\x17\" REPLACE<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
Now let’s check the time to live of the key before it expires:<\/p>\n\n\n\n
PTTL type<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(integer) 55940<\/pre>\n\n\n\n
Running PTTL<\/a><\/code> returns the current time to live, in milliseconds. We can alternatively use the TTL<\/a><\/code> command to return the time to live in seconds. Anyway, if we run PTTL<\/code> again, we can see that it has decremented:<\/p>\n\n\n\n
PTTL type<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(integer) 15263<\/pre>\n\n\n\n
We can alternatively specify the time to live as an absolute Unix timestamp (in milliseconds). When doing this, we need to add the ABSTTL<\/code> argument.<\/p>\n\n\n\n
The DUMP<\/code> Command<\/h2>\n\n\n\n
We can get serialised data by using the DUMP<\/code> command. The DUMP<\/a><\/code> command serialises the value stored at a specified key in a Redis-specific format and returns it to the user. <\/p>\n\n\n\n
Example:<\/p>\n\n\n\n
DUMP type<\/code><\/pre>\n\n\n\n
That returns the value of the key as a serialised value.<\/p>\n","protected":false},"excerpt":{"rendered":"
In Redis, the RESTORE command creates a key associated with a value that is obtained by deserialising the provided serialised value (obtained via the DUMP command). The serialisation format contains a 64-bit checksum, as well as the RDB version. The RESTORE command checks the RDB version and data checksum. If they don’t match an error … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[153],"tags":[154,20],"class_list":["post-26082","post","type-post","status-publish","format-standard","hentry","category-redis","tag-commands","tag-what-is"],"_links":{"self":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/26082","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=26082"}],"version-history":[{"count":5,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/26082\/revisions"}],"predecessor-version":[{"id":26443,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/26082\/revisions\/26443"}],"wp:attachment":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/media?parent=26082"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/categories?post=26082"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/tags?post=26082"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}