{"id":25959,"date":"2022-06-27T12:01:57","date_gmt":"2022-06-27T02:01:57","guid":{"rendered":"https:\/\/database.guide\/?p=25959"},"modified":"2022-06-27T12:01:57","modified_gmt":"2022-06-27T02:01:57","slug":"redis-incr-command-explained","status":"publish","type":"post","link":"https:\/\/database.guide\/redis-incr-command-explained\/","title":{"rendered":"Redis INCR Command Explained"},"content":{"rendered":"\n

In Redis, the INCR<\/code> command increments the value of a specified key by one.<\/p>\n\n\n\n

If the key doesn’t exist, INCR<\/code> creates the key with a value of 0<\/code> and then increments it by one.<\/p>\n\n\n\n

An error occurs if the key contains a value of the wrong type or contains a string that cannot be represented as integer. <\/p>\n\n\n\n\n\n\n\n

Syntax<\/h2>\n\n\n\n
INCR key<\/code><\/pre>\n\n\n\n
Where key<\/em><\/code> is the key to increment.<\/p>\n\n\n\n
Example<\/h2>\n\n\n\n
Suppose we set a key like this:<\/p>\n\n\n\n
SET pageviews \"20\"<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
Let’s quickly take a look at it:<\/p>\n\n\n\n
GET pageviews<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"20\"<\/pre>\n\n\n\n
OK, now let’s increment it by one:<\/p>\n\n\n\n
INCR pageviews<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(integer) 21<\/pre>\n\n\n\n
We get an integer reply with the value of the key after the INCR<\/code> operation was performed.<\/p>\n\n\n\n
Let’s run the GET<\/a><\/code> command again:<\/p>\n\n\n\n
GET pageviews<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"21\"<\/pre>\n\n\n\n
As expected, the original value has been incremented by one.<\/p>\n\n\n\n
Negative Values<\/h2>\n\n\n\n
Redis does not have a dedicated integer type. However, the string stored at the key is interpreted as a base-10 64 bit signed integer to execute the operation. Therefore, we can increment negative values just as we can increment positive values.<\/p>\n\n\n\n
Set a negative value:<\/p>\n\n\n\n
SET points \"-7\"<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
Let’s quickly take a look at it:<\/p>\n\n\n\n
GET points<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"-7\"<\/pre>\n\n\n\n
OK, now let’s increment it by one:<\/p>\n\n\n\n
INCR points<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(integer) -6<\/pre>\n\n\n\n
The value has been incremented by one.<\/p>\n\n\n\n
We can check this at any time by running the GET<\/code> command again:<\/p>\n\n\n\n
GET points<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"-6\"<\/pre>\n\n\n\n
When the Key Doesn’t Exist<\/h2>\n\n\n\n
If the key doesn’t exist, INCR<\/code> creates the key with a value of 0<\/code> and then increments it by one.<\/p>\n\n\n\n
Let’s delete our score<\/code> key:<\/p>\n\n\n\n
DEL points<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(integer) 1<\/pre>\n\n\n\n
The DEL<\/code> command returns the number of keys that were deleted – in this case 1.<\/p>\n\n\n\n
Now let’s try to increment that (non-existent) key:<\/p>\n\n\n\n
INCR points<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(integer) 1<\/pre>\n\n\n\n
So we can see that the points<\/code> key has been recreated with a value of 1.<\/p>\n\n\n\n
When the Value is the Wrong Type<\/h2>\n\n\n\n
As mentioned, an error occurs if the key contains a value of the wrong type or contains a string that cannot be represented as integer.<\/p>\n\n\n\n
To test this, let’s try incrementing a value that can’t be represented as an integer.<\/p>\n\n\n\n
Set the amount:<\/p>\n\n\n\n
SET pageviews \"Twenty\"<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
OK<\/pre>\n\n\n\n
Let’s quickly take a look at it:<\/p>\n\n\n\n
GET pageviews<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
\"Twenty\"<\/pre>\n\n\n\n
OK, now let’s try to increment it by one:<\/p>\n\n\n\n
INCR pageviews<\/code><\/pre>\n\n\n\n
Result:<\/p>\n\n\n\n
(error) ERR value is not an integer or out of range<\/pre>\n\n\n\n
An error occurred as expected.<\/p>\n","protected":false},"excerpt":{"rendered":"
In Redis, the INCR command increments the value of a specified key by one. If the key doesn’t exist, INCR creates the key with a value of 0 and then increments it by one. An error occurs if the key contains a value of the wrong type or contains a string that cannot be represented … Read more<\/a><\/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-25959","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\/25959","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=25959"}],"version-history":[{"count":5,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/25959\/revisions"}],"predecessor-version":[{"id":26272,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/posts\/25959\/revisions\/26272"}],"wp:attachment":[{"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/media?parent=25959"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/categories?post=25959"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/database.guide\/wp-json\/wp\/v2\/tags?post=25959"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}