Extension functions PostgreSQL

It is possible to write PostgreSQL functions in C. Because PostgreSQL itself is written in C, any extension functions can take advantage of the internal representation of RDMBS data. In fact, examples on which C functions might be based are the very functions used by the PostgreSQL RDMBS for processing standard SQL data. This puts any C functions on an equal footing with any built-in SQL functions. For this reason, C functions are the best choice when issues of speed are important. 

There is an open-source extension of PostgreSQL called pgchem.7 It uses C functions and OpenBabel. It implements some of the core functions described in Chapter 7. The names of the functions are not the same as the names used here. Using pgchem, it should be possible to perform most of the operations represented by the core functions described in this book. 

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