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39.5. Missing Features

The following features are currently missing from PL/Perl, but they would make welcome contributions.

  • PL/Perl functions cannot call each other directly (because they are anonymous subroutines inside Perl). There's presently no way for them to share global variables, either.

  • PL/Perl cannot be used to write trigger functions.

  • DBD::PgSPI or similar capability should be integrated into the standard PostgreSQL distribution.

For security reasons, PL/Perl executes functions called by any one SQL role in a separate Perl interpreter for that role. This prevents accidental or malicious interference by one user with the behavior of another user's PL/Perl functions. Each such interpreter has its own value of the %_SHARED variable and other global state. Thus, two PL/Perl functions will share the same value of %_SHARED if and only if they are executed by the same SQL role. In an application wherein a single session executes code under multiple SQL roles (via SECURITY DEFINER functions, use of SET ROLE, etc) you may need to take explicit steps to ensure that PL/Perl functions can share data via %_SHARED. To do that, make sure that functions that should communicate are owned by the same user, and mark them SECURITY DEFINER. You must of course take care that such functions can't be used to do anything unintended.