The catalog pg_proc stores information about functions (or procedures). The description of CREATE FUNCTION and Section 33.3 contain more information about the meaning of some columns.
The table contains data for aggregate functions as well as plain functions. If proisagg is true, there should be a matching row in pg_aggregate.
Implementation language or call interface of this function
proisagg
bool
Function is an aggregate function
prosecdef
bool
Function is a security definer (i.e., a "setuid" function)
proisstrict
bool
Function returns null if any call argument is null. In that case the function won't actually be called at all. Functions that are not "strict" must be prepared to handle null inputs.
proretset
bool
Function returns a set (i.e., multiple values of the specified data type)
provolatile
char
provolatile tells whether the function's result depends only on its input arguments, or is affected by outside factors. It is i for "immutable" functions, which always deliver the same result for the same inputs. It is s for "stable" functions, whose results (for fixed inputs) do not change within a scan. It is v for "volatile" functions, whose results may change at any time. (Use v also for functions with side-effects, so that calls to them cannot get optimized away.)
An array with the data types of the function arguments
prosrc
text
This tells the function handler how to invoke the function. It might be the actual source code of the function for interpreted languages, a link symbol, a file name, or just about anything else, depending on the implementation language/call convention.
probin
bytea
Additional information about how to invoke the function. Again, the interpretation is language-specific.
proacl
aclitem[]
Access privileges
prosrc contains the function's C-language name (link symbol) for compiled functions, both built-in and dynamically loaded. For all other language types, prosrc contains the function's source text. probin is unused except for dynamically-loaded C functions, for which it gives the name of the shared library file containing the function.
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