PostgreSQL Extensions - Design and Use of Relational Databases in Chemistry - page 120

Table 10.1 Core Extension Functions

Function Name Returns Arguments

valid Boolean smiles

cansmiles Text smiles

isosmiles Text smiles

keksmiles Text smiles

matches Boolean smiles, smarts

list_matches Integer[] smiles, smarts, imatch, istart

count_matches Integer smiles, smarts

molfile_to_smiles Text molfile text

smiles_to_molfile Text smiles text

fp Bit smiles, nbits, maxpath

contains Boolean bit, bit

function is not implemented using PerlMol or FROWNS. The keksmiles
function is not implemented using FROWNS.

10.5.4 C Language Functions
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.
The CHORD 6 chemical cartridge is a commercial product from
gNova, Inc. It is written using C functions and the OEChem toolkit from
OpenEye. It provides the core functions discussed in this topic, such as
cansmiles , matches , count _ matches , list _ matches , smiles _
to _ molfile , molfile _ to _ smiles , and xform . CHORD makes it
possible to efficiently process RDBMS tables containing many millions of
chemical structures.
Unlike the procedural languages discussed above, C language func-
tions are compiled separately. The code itself is not included in the SQL
create function command. Instead, the create function command
refers to a compiled object such as shared object (.so) file located in some
directory on the server running the RDBMS. For example, the CHORD
oe _ smiles function is defined as follows.

Create or Replace Function oe_smiles(Text, integer)
Returns Text As 'gnova', 'oe_anysmiles'
Language 'c' Immutable Strict;
Comment On Function oe_smiles(Text, integer)
Is 'smiles to smiles of various types';