---
title: "Functions for delaying execution"
url: "https://docs.yugabyte.com/stable/api/ysql/datatypes/type_datetime/functions/delaying-execution/"
---

# Functions for delaying execution

The semantics of the functions for delaying execution. [YSQL]

The three functions *pg\_sleep(double precision)*, *pg\_sleep\_for(interval)*, and *pg\_sleep\_until(timestamp\_tz)* are understood simply. The argument of *pg\_sleep()* is interpreted as the number of seconds for which to sleep. Because each has a formal parameter with a different data type, they could all have been implemented as overloads of a single function. Presumably, somebody chose to use different names somewhat whimsically. The fact that they are functions allows them to be invoked within the same SQL statement, just as the demonstration of the semantic difference between *statement\_timestamp()* and *clock\_timestamp()* does above. It's probably more common to use them within PL/pgSQL code. A procedure would have been more natural here than a function. But this has no practical consequence because the invocation *perform pg\_sleep(n)* comes to the rescue.

Notice that you cannot declare a PL/pgSQL variable with the data type *void*. (The attempt causes the *0A000* error. This is mapped to the *feature\_not\_supported* exception.) If you need to include a *pg\_sleep()* invocation in a *select into* SQL statement in PL/pgSQL code, then you should typecast its return value to *text*. (This typecast produces the empty string.)

### function pg\_sleep() returns void

Here is a simple example:

```plpgsql
select (pg_sleep(1.0::double precision)::text = '')::text;
```

The result is *true*.

### function pg\_sleep\_for() returns void

Here is a simple example:

```plpgsql
select (pg_sleep_for(make_interval(secs=>1))::text = '')::text;
```

The result is *true*.

### function pg\_sleep\_until() returns void

Here is a simple example:

```plpgsql
select (pg_sleep_until( (clock_timestamp() + make_interval(secs=>1))::timestamptz )::text = '')::text;
```

The result is *true*. Notice that *pg\_sleep\_until()* function has no overloads other than the one with the single *timestamptz* parameter. This is yet another reason always to use *timestamptz* for moment values and only to convert to other data type values on the fly if the need arises.