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README.md

Interface to the PostgreSQL Database Server from [GNU|SWI] Prolog

PREDICATES

pl_pgsql_connect/6 (+host,+port,+user,+password,+dbname,-connection) connect to the server on host as user with password, returns the connection id, which must be used in further request.

pl_pgsql_disconnect/1 (+connection) disconnect and free allocated memory

pl_pgsql_query/2 (+connection,+query) sends the query to the server. There is no result. Used for insert/update/delete.

pl_pgsql_query/3 (+connection,+query,-result) sends the query to the server. This predicate is backtrackable and succeeds for every row in the result set of the query.

pl_pgsql_query_all/3 (+connection,+query,-results) sends the query to the server. This predicate is deterministic and collects all rows from the result set of the query.

EXAMPLES

load module:

use_module(sbcl(pgsql)).
  1. something that works:
| ?- pl_pgsql_connect("localhost",5432,"testuser","my_password","postgres",DBx),
     pl_pgsql_query(DBx,"select 3*7",Result),
     format("result: ~d~n",Result),
     pl_pgsql_disconnect(DBx).
  1. better: we should always succeed a query to disconnect from the db at the end
  run_query(DBx) :-
     pl_pgsql_query(DBx,"select nr,name,city from addresses",Result),
     format("~d: ~s lives in ~s~n",Result),
     fail,  % to backtrack over next row in Result

  run_query(_DBx).  % always succeed

| ?- pl_pgsql_connect("localhost",5432,"test,"my_password","the_db",DBx),
     run_query(DBx),
     pl_pgsql_disconnect(DBx).

HOW TO COMPILE

aclocal --force && autoheader --force && autoconf --force

then run

./configure

then call make

INSTALLATION

copy the plpgsql- file to where your search path points to. I have added the following in the file ~/.config/swi-prolog/init.pl:

:- assertz(file_search_path(sbcl,'/home//lib/sbcl')).

also copy the src/pgsql.qlf to this directory

COMMENTS

Arguments that are strings are passed as character code lists. Same for strings in the result. Have a look at the code if you want to change this behaviour and get returned atoms for strings.

On the mips/IRIX there were quite a few problems with gprolog tagged integers. As I pass the pl_pgsql_?? routines the address of the connection structure in C and this address has the 29th bit set the value is a negative number after tagging (left shift of 3 bits). By Un_Tagging this number, the processor thinks it should still be a negative number after right shifting of 3 bits. Hence that does not work. I did something very bad: the address is divided by two (because it anyway is aligned on some even byte boundery) and then passed to gprolog. That helps but is quite a hack.

LICENSE

Copyright (C) 1999-2023 Alexander Diemand

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.