Functions return information from the database. Except for Vertica meta-functions, you can use a function anywhere an expression is allowed.
This section describes functions that Vertica supports. The Behavior Type section on each reference page categorizes the function's return behavior as one or more of the following:
Immutable (invariant): When run with a given set of arguments, immutable functions always produce the same result, regardless of environment or session settings such as locale.
Stable: When run with a given set of arguments, stable functions produce the same result within a single query or scan operation. However, a stable function can produce different results when issued under different environments or at different times, such as change of locale and time zone—for example, SYSDATE.
Volatile: Regardless of their arguments or environment, volatile functions can return a different result with each invocation—for example, UUID_GENERATE.
Unless otherwise noted, Vertica meta-functions are volatile; thus, reference pages for these functions omit a Behavior Type section.