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Perl can be convinced to execute user-defined code during compilation of a plperl function (or at least a plperlu function). That's not such a big problem as long as the activity is confined within the Perl interpreter, and it's not clear we could do anything about that anyway. However, if such code tries to use plperl's SPI functions, we have a bigger problem. In the first place, those functions are likely to crash because current_call_data->prodesc isn't set up yet. In the second place, because it isn't set up, we lack critical info such as whether the function is supposed to be read-only. And in the third place, this path allows code execution during function validation, which is strongly discouraged because of the potential for security exploits. Hence, reject execution of the SPI functions until compilation is finished. While here, add check_spi_usage_allowed() calls to various functions that hadn't gotten the memo about checking that. I think that perhaps plperl_sv_to_literal may have been intentionally omitted on the grounds that it was safe at the time; but if so, the addition of transforms functionality changed that. The others are more recently added and seem to be flat-out oversights. Per report from Mark Murawski. Back-patch to all supported branches. Discussion: https://postgr.es/m/9acdf918-7fff-4f40-f750-2ffa84f083d2@intellasoft.net
src/pl/plperl/README PL/Perl allows you to write PostgreSQL functions and procedures in Perl. To include PL/Perl in the build use './configure --with-perl'. To build from this directory use 'make all; make install'. libperl must have been built as a shared library, which is usually not the case in standard installations. Consult the PostgreSQL User's Guide and the INSTALL file in the top-level directory of the source distribution for more information.