When setting a timeout on a key in Redis, we have the option of setting the timeout only if it’s less than the existing timeout. We can do this with the LT option of commands such as EXPIRE, EXPIREAT, PEXPIRE, and PEXPIREAT.
Subtract Seconds from a Time Value in PostgreSQL
In PostgreSQL, we can use the - operator to subtract one or more seconds from a time value.
By “time” value, this could be an actual time value, a timestamp, or an interval. We can also subtract seconds from a date value or a date and time combination.
How to Return a Key’s Value and Set its Expiry in a Single Operation in Redis
In Redis, typically when we want to return a key’s value, we use the GET command. But there’s also a GETEX command (introduced in Redis 6.2.0) that allows us to get the value and return it’s expiry at the same time.
Redis SDIFFSTORE Command Explained
In Redis, the SDIFFSTORE command works just like the SDIFF command, except that instead of returning the result, it stores it in the key that we specify. The destination key will then hold the members of the set resulting from the difference between the first set and all the successive sets.
5 Ways to See if a Table has a Generated Column in MySQL
MySQL supports generated columns. If you’re not sure whether a table has a generated column or not, you can check it using any of the following methods.
Continue readingRedis SDIFF Command Explained
In Redis, the SDIFF command returns the members of the set resulting from the difference between the first set and all the successive sets. In other words, it returns all members of the first set that aren’t in any of the successive sets.
How to Return the Expiry Time as a Unix Timestamp in Redis
In Redis, we have several options for returning the expiry time of a key. One option from Redis 7.0.0 and above is to return it as a Unix timestamp.
When returning the expiry as a Unix timestamp, we can have it returned in seconds or milliseconds. To return it in seconds, we can use the EXPIRETIME command. To return it in milliseconds, we can use the PEXPIRETIME command.
2 Ways to Set a Redis Key Only When it Doesn’t Already Exist
In Redis, it’s possible to set a key only if it doesn’t already exist. As with most things, there’s more than one way to do this.
Continue readingHow to Set an Expiry Only When the New Expiry is Greater Than the Existing Expiry in Redis
Redis 7.0.0 introduced some potentially useful options for setting timeouts on keys. One of these is the GT option, which allows us to set the expiry only if the new expiry is greater than the existing one.
The GT option is available for commands such as EXPIRE, EXPIREAT, PEXPIRE, and PEXPIREAT.
Redis SCARD Command Explained
In Redis, the SCARD command returns the number of members in the specified set. This is referred to as the cardinality of the set.