After upgrading PostgreSQL from 7.4 to 8.2 it started crashing sporadically with the following entries in the log file:

LOG:  server process (pid 21460) was terminated by signal 11
LOG:  terminating any other active server processes
LOG:  all server processes terminated; reinitializing shared memory and semaphores

CAUSE:

There were changes between PostgreSQL releases in functions definition used by pgcrypto module.

According to [1] and [3] in PostgreSQL 8.0 the pgcrypto functions were non-strict and checked for NULLs, in PostgreSQL 8.1 they were made STRICT, in PostgreSQL 8.2 the NULL checks were removed from code.

SOLUTION:

In order to correct the problem these functions are needed to be recreated. Required SQL commands are defined in pgcrypto.sql which is usually located in
/usr/local/pgsql/share/contrib when pgcrypto is installed.

psql -d DBNAME -f /usr/local/pgsql/share/contrib/pgcrypto.sql

Also it is a good idea to add functions to template1 database if you use pgcrypto often. template1 is the default source database name when using CREATE DATABASE command.

REFERENCES:

1. http://marc.info/?l=postgresql-general&m=118794006505296&w=2
2. http://www.mail-archive.com/pgsql-hackers@postgresql.org/msg109917.html
3. http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/pgcrypto/pgcrypto.sql.in