When setting an expiry for an existing key in Redis, we now have the option to set the expiry only if the key doesn’t already have an expiry. That’s because Redis 7.0.0 introduced some new options that allows us to do this and other things.
In this case, we can use the NX option when setting the expiry to specify that the expiry should only be set if the key doesn’t already have an expiry. We can use this option on commands such as EXPIRE, EXPIREAT, PEXPIRE, and PEXPIREAT.
In Redis, the LPOS command returns the index of matching elements inside a list.
In PostgreSQL, we can use the + operator to add one or more seconds to a time value.
By “time” value, this could be an actual time value, a timestamp, or an interval. We can also add seconds to a date value or a date and time combination.
In Redis, the BLMOVE command is the blocking variant of LMOVE.
When the specified list contains elements, it atomically returns and removes either the first or last element of the given source list, and pushes the element at either the first or last element of the specified destination list. Whether it’s the first or last element depends on the arguments passed to the command.
Continue readingIn Redis, the LMOVE command atomically returns and removes either the first or last element of the given source list, and pushes the element at either the first or last element of the specified destination list.
Whether it’s the first or last element depends on the arguments passed to the command.
The LMOVE command can be used in place of the RPOPLPUSH command, which has been deprecated since Redis 6.2.0.
In Redis, the LINDEX command returns the element at the specified index at the specified key.
In Redis, the LLEN command returns the length of the list stored at the specified key.
In Redis, the LRANGE command returns the specified elements of the list stored at the specified key.
The command requires us to specify a start and stop position for the elements to return. These are zero based indexes, so 0 is the first element in the list.
We can specify -1 for the last element in the list.
In Redis, the LMPOP command pops one or more elements from the first non-empty list key from the list of provided key names.
The LMPOP command is similar to LPOP, except that it can accept multiple keys. It’s also similar to BLPOP (which accepts multiple keys), except that it can pop multiple elements (BLPOP can only pop one element).
A generated column is a database column whose value is an expression. Therefore, the value of the generated column is usually derived (for example, it could be derived from values in other columns).
Generated columns are also sometimes referred to as computed columns or virtual columns.
Creating a generated column in MariaDB is essentially the same as creating a normal column. The difference is that the definition of the generated column contains an expression that determines the column’s value.
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