One solution for Packages in Postgre

Hi Posgre Developers,

Common table for all packages

table Package_Variable_Table :-
For Storing Package public and private Variables This table will be
common for all packages.
to distinguish between different sessions, it uses unique session id. Get
and Set functions used to access these variables.

Common Functions for all packages
1) function - Current_Session()
Function for getting current unique session id.
Reference :
http://archives.postgresql.org/pgsql-hackers/2006-06/msg01557.php

2)function - IsValidSession( sid character varying)
common for all packages. function for checking if given sessionid is
valid, returns true or false, if returns false then data from public and
local pack table data for that sesseion can be deleted.
sid = unique session id

3)function - IsPackLoaded( sid character varying )
common for all packages. function for checking if given sessionid 's
package is initialized or not, returns true or false, if returns false
then pack initialized -> global/private var values are set.
sid = unique session id

4)function - Delete_invld_pack_data()
Common for all packages .function for deleting invalid session' public and
private variable data.

Package specific additional functions

In addition to the procedure, functions in the oracle package( which will
be created as functions); below additional functions will be required for
each package -

1) Pack_Spec_THMS_Pack() - function to initialze package specification if
already not done (for setting any public private variable values
initially). Internally this function calls Delete_invld_pack_data for
deleting unnecessary data from table - Package_Variable_Table

2)GetPublicVar_THMS_Pack ( v_VariableName character varying ) One function
for getting value of all public variable of the package. this will
return char type; which can be typecasted if required. This function calls
Pack_Spec_THMS_Pack().

3)SetPublicVar_THMS_Pack( v_VariableName character varying,
v_VariableValue character varying)One function for setting value of each
private variable of the package. This function calls Pack_Spec_THMS_Pack()
.

Package functions/procedures
Each function has to call Pack_Spec_THMS_Pack() function at start, to
initialize package data.

How it works:
Whenever any procedure/function of package is called OR whenever any of
the public variable is accessed( that is to be done through get or set
functions ) ,
package initialization function - Pack_Spec_THMS_Pack() is get called, it
first removes unnecessary data from Package_Variable_Table table (possibly
for other packages also whose session' ended). Then it checks in the table
Package_Variable_Table if any entry for current session is there or not,
if not it inserts new data for public/private variables and initializes.

access to public variables of package - through get /set functions.
access to private variables of package - function and procedures can
directly access table Package_Variable_Table for this.

=============================================================================

By using temp tables in PostgreSQL (similar to global temp tables in
Oracle. The key difference is that in PostgreSQL, you can create them in
the session), you may be able to avoid the work of deleting data, storing
sessions etc. Here is an example of how you can create a temp table in a
session.
postgres=# \d myttmp
Did not find any relation named "myttmp".

postgres=# select now() into myttmp;
SELECT
postgres=# \d myttmp
Table "public.myttmp"
Column | Type | Modifiers
--------+--------------------------+-----------
now | timestamp with time zone |

The data won't be visible to other sessions and thus your package
variables not visible in other sessions. See link for details -
http://www.postgresql.org/files/documentation/books/aw_pgsql/node119.html
Please have a look at this too....
http://www.postgresql.org/docs/8.3/static/plpgsql-porting.html

Regards,
Jayadevan

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venkatrao.b@tcs.com writes:

I am new to Postgre. We are migrating an oracle db to postgre. In
oracle we have used so many packages. As per my understanding, there
is no oracle package like functionality in postgre. I was just trying
to find some way to migrate ocale packages to postgre.

This has been discussed already in the past, see the archives. In short,
Oracle Packages are not something the PostgreSQL community intend to
offer directly, even if we have some plans to provide better tools for
managing what we have and call "extensions".

The following shows the current state of the design, the code is yet to
be written, and that could happen this very year (it obviously missed
9.0).

http://wiki.postgresql.org/wiki/ExtensionPackaging

You will note that this document refers to C-coded extensions, but is
compatible with an extension not containing one of those. It could well
be that the feature you're missing is offered by this design.

Regards,
--
dim

Thanks a lot Jayadevan.

I was unaware of temp table kind of functionality exists in postgres.
Now i updated functions as follows-
I have one question - if is there any better way of checking if temporary
table already created for the given session package(other than one i used
to capture as exception).
###################################################################

--++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-- Package specific
CREATE OR REPLACE FUNCTION "MM".Pack_Spec_THMS_Pack()
RETURNS numeric AS
$BODY$
DECLARE
v_output numeric := 1 ;
v_SessionID character varying(500) ;
v_packName character varying(50) := 'THMS_Pack';
v_cnt numeric := 0 ;
v_tmp boolean := false ;
BEGIN

begin

create temporary table Tmp_Package_Variable_Table
(
Var_Name character varying(50),
Var_Value character varying(50),
Var_DataType character varying(50),
Var_Type character varying(50)--public or private
);

exception
when others then return 0 ;
end ;

-- insert global variables for package with their initial values
-- Glbl_Var_number
insert into Tmp_Package_Variable_Table
(
Var_Name,
Var_Value,
Var_DataType,
Var_Type
)
values (
'Glbl_Var_number',
'10',
'numeric',
'public'
);

-- Glbl_Var_char
insert into Tmp_Package_Variable_Table
(
Var_Name,
Var_Value,
Var_DataType,
Var_Type
)
values (

'Glbl_Var_char',
null,
'character varying',
'public'
);

-- insert private variables for package with their initial values
-- Locl_Var_number

insert into Tmp_Package_Variable_Table
(
Var_Name,
Var_Value,
Var_DataType,
Var_Type
)
values (

'Locl_Var_number',
'20',
'numeric',
'private'
);

-- Locl_Var_char
insert into Tmp_Package_Variable_Table
(
Var_Name,
Var_Value,
Var_DataType,
Var_Type
)
values (

'Locl_Var_char',
'localpack',
'character varying',
'private'
);
RETURN v_output;
END;
$BODY$ LANGUAGE 'plpgsql' VOLATILE

--++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

CREATE OR REPLACE FUNCTION "MM".GetPublicVar_THMS_Pack( v_VariableName
character varying )
RETURNS character varying AS
$BODY$
DECLARE
v_output character varying(500) ;
v_cnt numeric := 0;
v_tmp numeric := 0;
BEGIN
--set package initializtion
v_tmp := "MM".Pack_Spec_THMS_Pack();

select count(1)
into v_cnt
from Tmp_Package_Variable_Table
where Var_Name = v_VariableName
and Var_Type = 'public'
;
if v_cnt>0 then
select Var_Value
into v_output
from Tmp_Package_Variable_Table
where Var_Name = v_VariableName
and Var_Type = 'public'
;
else
v_output := null;
end if;

RETURN v_output;
END;
$BODY$ LANGUAGE 'plpgsql' VOLATILE

--++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

CREATE OR REPLACE FUNCTION "MM".SetPublicVar_THMS_Pack( v_VariableName
character varying, v_VariableValue character varying)
RETURNS numeric AS
$BODY$
DECLARE
v_output numeric := 1;
v_cnt numeric := 0;
v_tmp numeric := 0 ;
BEGIN

--set package initializtion
v_tmp := "MM".Pack_Spec_THMS_Pack();

update Tmp_Package_Variable_Table
set Var_Value = v_VariableValue
where Var_Name = v_VariableName
and Var_Type = 'public'
;

RETURN v_output;
END;
$BODY$ LANGUAGE 'plpgsql' VOLATILE
------------------------------------------------------------------------------

####################################################################

Thanks again.
Venkat
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