Re: dblink_ora - a first shot on Oracle ... - Mailing list pgsql-hackers

Hans-Jürgen Schönig wrote:
> Thanks a lot. I will integrate named connections as proposed by the most 
> recent version of dblink as soon as possible.
> Thanks for doing the configure stuff. What we need is Oracle's OCI 
> interface and libsqlora (http://www.poitschke.de/libsqlora8/).

I was thinking that we should be merging dblink_ora (and eventually 
jdbclink) into dblink. If you wanted to start down that road, here are 
my thoughts on how that should be done.

dblink functions can be roughly divided into three groups. I'll address 
each one separately:

1) connection related
   SQL interface:   --------------   1.a dblink_connect (text <conn_str>)   1.b dblink_connect (text <conn_name>, text
<conn_str>)  1.c dblink_disconnect ()   1.d dblink_disconnect (text <conn_name>)
 
   To these I would add:   1.e  dblink_connect (text <name>, text <conn_str>, text <conn_type>)
   Acceptable values for <conn_type> would be 'postgres', 'oracle', and   eventually 'jdbc', non-case-sensitive. New
typescould be added to   this list later if/when other connection types are developed.
 
   1.a and 1.b would default to type 'postgres'. Hence the only way to   get a non-postgres connection would be to use
anamed persistent   connection, but I think that makes sense anyway.
 
   Implementation:   ---------------   There are actually only two underlying functions, dblink_connect()   and
dblink_disconnect().Both of these should be modified so that   the mode (i.e. unnamed_default, named_default,
named_with_type)is   discovered based on the arguments, then the real work farmed out to   connection type specific
functions.I'm not entirely sure how it   should be handled when, for instance, the oracle library is not found   by
configure.I suppose in that case you can use #ifdef's to provide   stubs with appropriate error messages.
 

2) connection consumers
   SQL interface:   --------------   2.a dblink_open (text <cursor_name>, text <sql>)   2.b dblink_fetch (text
<cursor_name>,int <num>)   2.c dblink_close (text <cursor_name>)   2.d dblink (text <sql>)   2.e dblink_exec (text
<sql>)  2.f dblink_open (text <conn_name>, text <cursor_name>, text <sql>)   2.g dblink_fetch (text <conn_name>, text
<cursor_name>,int <num>)   2.h dblink_close (text <conn_name>, text <cursor_name>)   2.i dblink (text
<conn_name_or_str>,text <sql>)   2.j dblink_exec (text <conn_name_or_str>, text <sql>)
 
   2.a - 2.e all use the unnamed connection and therefore only apply   to connections of type 'postgres'
   2.f - 2.h all use named connections
   2.i and 2.j can use named connections or connection strings
   The existing named connections functions can be made to work with   <conn_type> == 'oracle', etc. It probably makes
senseto add two   functions:   2.k dblink (text <conn_str>, text <conn_type>, text <sql>)   2.l dblink_exec (text
<conn_str>,text <conn_type>, text <sql>)   This would allow dynamic specification of connections to   connection types
otherthan 'postgres'.
 
   Implementation:   ---------------   Similar to the above, there is only one underlying function for each   SQL
functionname. These should be modified in a similar manner as   the connection functions.
 

3) miscellaneous utility functions
   SQL interface:   --------------   3.a dblink_get_pkey   3.b dblink_build_sql_insert   3.c dblink_build_sql_delete
3.ddblink_build_sql_update   3.e dblink_current_query
 
   These functions don't use libpq, they use SPI or other internals.   I wouldn't try to support other types of
databasesfor them.
 


> Joe, you have told me some time ago that you are planning some sort of 
> connection table which tells dblink to establish some connections 
> automatically. Did you work on that?
No, I wouldn't worry too much about that right now.

Comments?

Joe