In the previous chapter, we introduced you to the possibilities of untrusted pluggable languages being available to a PostgreSQL developer to achieve things impossible in most other relational databases.

While using a pluggable scripting language is enough for a large class of problems, there are two main categories, where they may fall short: performance and depth of functionality.

Most scripting languages are quite a bit slower than optimized C code when executing the same algorithms. For a single function, this may not be the case because common things such as dictionary lookups or string matching have been optimized so well over the years. But in general, C code will be faster than scripted code. Also, in cases where the function is called millions of times per query, the overhead of actually calling the function and converting the arguments and return values to and from the scripting language counterparts can be a significant portion of the run...