A Redis key can have an optional timeout, which makes the key expire after a certain amount of time, or at a certain time. We can use a couple of methods to remove any timeout associated with a key.
Here are two ways to remove a key’s expiry in Redis.
Continue readingWhen using the SET command to set a key in Redis, we can use the GET option to return its old value. This allows us to update the value of a key while returning the value that we’re replacing it with.
Note that this option was introduced in Redis 7.0.0, so if it doesn’t work, check your Redis version. If using an earlier version, try the GETSET command instead (which is deprecated from Redis version 6.2.0).
In SQLite, we can use the DATE() function to subtract one or more months from a date.
For datetime values, we can use the DATETIME() function.
In Redis, we can use the OBECT IDLETIME command to check how many seconds has passed since the last access to a given key.
In SQLite, the CASE expression compares a list of conditions and returns one of multiple possible expressions.
The CASE expression is included in the SQL standard (ISO/IEC 9075), and most major RDBMSs support it.
In Redis, we have several options for decrementing a key. By this, I mean, reducing the value of a key by one or more. For example, if we set a key to 15, we can decrement it by 1 to make 14. Or we can increment it by whatever amount we desire.
Continue readingIn Redis, the LTRIM command allows us to trim a list to a specified number of elements. We specify the starting and ending index, which is used to trim the list to just that range.
We can use SQLite’s DATE() function to return the first, second, third, fourth, etc instance of a given day within a given year.
We can use the same technique to return the first Monday of each month in the year.
It’s not limited to Monday though. The same techniques can be used on Tuesday, Wednesday, Thursday, Friday, etc.
Continue readingIn Redis, the LSET command allows us to set a list element to a different value, based on its index.
In Redis, we can use the LREM command to remove one or more elements from a list. The number of elements removed depends on the arguments we pass.