I have a little problem when calling a Postgresql function in Delphi with FireDAC.
The Postgresql function has the following definition:
CREATE OR REPLACE FUNCTION public."pgpDecryptMe" (
todecode text
)
RETURNS text AS
$body$
DECLARE
PGPPrivate TEXT;
BEGIN
...
So it expects a "text" value and returns a "text" value.
I can call it with a long text parameter (over 900 character) and it returns the correct value in any sql admin tool without any problems.
select "pgpDecryptMe"('c1c04c030...a378624e6a659a20765') as Decrypt
But calling it in Delphi with the following code:
PGQuery.SQL.Text := 'select "pgpDecryptMe"(:test) as testvalue';
PGQuery.ParamByName('test').AsString := 'c1c04c030...a378624e6a659a20765';
PGQuery.Open();
Gives me the following error message:
[FireDAC][DatS]-2. Object [id] is not found
I googled and searched here but can't find any solution for the problem.
It is probably something very small I can't see :-(
I am working with Delphi XE7 and PostgreSQL 9.3
Ok, now I got it working.
It looks like it needed an additional index field name which doesn't really make sense because it just returned one value...
So it worked when I changed my code to the following:
PGQuery.SQL.Text := 'select "pgpDecryptMe"(:test) as testvalue';
PGQuery.ParamByName('test').AsString := 'c1c04c030...a378624e6a659a20765';
PGQuery.IndexFieldNames := 'testvalue';
PGQuery.Open();
Related
Tell me, please, why does the empty value come?
To send a request, I use SoapUI 5.5.
But :body is not null.
Do I need to do something in the settings of ORDS?
DECLARE
--b_body BLOB := :body;
c_body CLOB := :body_text;
BEGIN
if :body_text is null then
htp.print('EMPTY');
end if;
END;
As it says in documentation https://docs.oracle.com/en/database/oracle/oracle-rest-data-services/18.3/aelig/implicit-parameters.html#GUID-76A23568-EA67-4375-A4AA-880E1D160D27, for each implicit parameter :body and :body_text "if it is dereferenced more than once, then the second and subsequent dereferences will appear to be empty."
So, change your code like this:
DECLARE
--b_body BLOB := :body;
c_body CLOB := :body_text;
BEGIN
if c_body is null then
htp.print('EMPTY');
end if;
END;
If I remember correct it's not a good idea to use both binds in 1 code block...
If ORDS checks that you're using :body, :body_text is not populated (I think because of the overall performance of converting a blob to clob).
So just use :body_text and you should be fine!
This symptom may result from creating RESTful Services via older versions of the APEX SQL Workshop interface. APEX 5.1 certainly exhibits this behaviour, possibly others. If you are unable to upgrade APEX, use SQL Developer to create your ORDS modules.
Common sense dictates that SQL query strings should never be assembled by hand. Thus, all database interfaces offer parameter substitution, and all users use it, without exceptions.*
I'm using PostgreSQL v10.5, nodejs v8.12.0, node-postgres 7.6.1.
Parameter substitution works as expected for SELECT statements:
> await db.query("select from users where id = 'mic'");
(success, 1 row returned)
> await db.query("select from users where id = $1", ["mic"]);
(success, 1 row returned)
But it doesn't work for LISTEN statements:
> await db.query("listen topicname");
(success)
> await db.query("listen $1", ["topicname"]);
(error: syntax error at or near "$1")
The name of the topic I want to listen to is dynamic. It is coming from semi-trustworthy sources, which should not be user-controllable. But why go against all established best practice and take any chances?
Unfortunately, from my tests I fear that PostgreSQL simply can't do parameter substitution for LISTEN queries.
Is there any solution or workaround for this?
*) This statement may only be true in some utopic future society.
I don't have enough reputation to comment on the answer, but the proposed solution doesn't work for me.
Using %L results in a quoted string, which causes the following error:
ERROR: syntax error at or near "'topic'"
The %I format should be used instead (SQL identifier, this is documented for table and column names, but it also works for the channel name,). You can also use the quote_ident function. See the documentation on creating dynamic queries here.
The following PL/pgSQL function works for us:
CREATE OR REPLACE FUNCTION listenForChannel(
channel_ TEXT
) RETURNS VOID AS $$
BEGIN
EXECUTE format('LISTEN %I', channel_);
END
$$ LANGUAGE PLPGSQL;
You are right that this cannot be done in PostgreSQL.
As a workaround, write a PL/pgSQL function that uses dynamic SQL like this:
EXECUTE format('LISTEN %L', topicname);
The format function escapes strings properly; in this case, the %L format that produces a properly quoted string Literal is the appropriate one.
I am struggling to figure out how to best handle the return of results or errors to my application from Postgres stored functions.
Consider the following contrived psudeocode example:
app.get_resource(_username text)
RETURNS <???>
BEGIN
IF ([ ..user exists.. ] = FALSE) THEN
RETURN 'ERR_USER_NOT_FOUND';
END IF;
IF ([ ..user has permission.. ] = FALSE) THEN
RETURN 'ERR_NO_PERMISSION';
END IF;
-- Return the full user object.
RETURN QUERY( SELECT 1
FROM app.resources
WHERE app.resources.owner = _username);
END
The function can fail with a specific error or succeed and return 0 or more resources.
At first I tried creating a custom type to always use as a standard return type in eachh function:
CREATE TYPE app.appresult AS (
success boolean,
error text,
result anyelement
);
Postgres does not allow this however:
[42P16] ERROR: column "result" has pseudo-type anyelement
I then discovered OUT parameters and attempted the following uses:
CREATE OR REPLACE FUNCTION app.get_resource(
IN _username text,
OUT _result app.appresult -- Custom type
-- {success bool, error text}
)
RETURNS SETOF record
AS
$$
BEGIN
IF 1 = 1 THEN -- just a test
_result.success = false;
_result.error = 'ERROR_ERROR';
RETURN NULL;
END IF;
RETURN QUERY(SELECT * FROM app.resources);
END;
$$
LANGUAGE 'plpgsql' VOLATILE;
Postgres doesn't like this either:
[42P13] ERROR: function result type must be app.appresult because of OUT parameters
Also tried a similar function but reversed: Returning a custom app.appresult object and setting the OUT param to "SETOF RECORD". This was also not allowed.
Lastly i looked into Postgres exception handling using
RAISE EXCEPTION 'ERR_MY_ERROR';
So in the example function, i'd just raise this error and return.
This resulted in the driver sending back the error as:
"ERROR: ERR_MY_ERROR\nCONTEXT: PL/pgSQL function app.test(text) line 6 at RAISE\n(P0001)"
This is easy enough to parse but doing things this way feels wrong.
What is the best way to solve this problem?
Is it possible to have a custom AppResult object that i could return?
Something like:
{ success bool, error text, result <whatever type> }
//Edit 1 //
I think I'm leaning more towards #Laurenz Albe solution.
My main goal is simple: Call a stored procedure which can return either an error or some data.
Using RAISE seems to accomplish this and the C++ driver allows easy checking for an error condition returned from a query.
if ([error code returned from the query] == 90100)
{
// 1. Parse out my overly verbose error from the raw driver
// error string.
// 2. Handle the error.
}
I'm also wondering about using custom SQLSTATE codes instead of parsing the driver string.
Throwing '__404' might mean that during the course of my SPs execution, it could not continue because some record needed was not found.
When calling the sql function from my app, i have a general idea of what it failing with a '__404' would mean and how to handle it. This avoids the additional step of parsing driver error string.
I can also see the potential of this being a bad idea.
Bedtime reading:
https://www.postgresql.org/docs/current/static/errcodes-appendix.html
This is slightly opinion based, but I think that throwing an error is the best and most elegant solution. That is what errors are for!
To distinguish various error messages, you could use SQLSTATEs that start with 6, 8 or 9 (these are not used), then you don't have to depend on the wording of the error message.
You can raise such an error with
RAISE EXCEPTION SQLSTATE '90001' USING MESSAGE = 'my own error';
We do something similar to what you're trying to do, but we use TEXT rather than ANYELEMENT, because (almost?) any type can be cast to TEXT and back. So our type looks something like:
(errors our_error_type[], result TEXT)
The function which returns this stores errors in the errors array (it's just some custom error type), and can store the result (cast to text) in the result field.
The calling function knows what type it expects, so it can first check the errors array to see if any errors were returned, and if not it can cast the result value to the expected return type.
As a general observation, I think exceptions are more elegant (possibly because I come from a c# background). The only problem is in plpgsql exception handling is (relatively) slow, so it depends on the context - if you're running something many times in a loop, I would prefer a solution that doesn't use exception handling; if it's a single call, and/or especially when you want it to abort, I prefer raising an exception. In practice we use both at various points throughout our call stacks.
And as Laurenz Albe pointed out, you're not meant to "parse" exceptions, so much as raise an exception with specific values in specific fields, which the function that catches the exception can then extract and act on directly.
As an example:
Setup:
CREATE TABLE my_table (id INTEGER, txt TEXT);
INSERT INTO my_table VALUES (1,'blah');
CREATE TYPE my_type AS (result TEXT);
CREATE OR REPLACE FUNCTION my_func()
RETURNS my_type AS
$BODY$
DECLARE
m my_type;
BEGIN
SELECT my_table::TEXT
INTO m.result
FROM my_table;
RETURN m;
END
$BODY$
LANGUAGE plpgsql STABLE;
Run:
SELECT (m.result::my_table).*
FROM my_func() AS m
Result:
| id | txt |
-------------
| 1 | blah |
I just noticed that I could alter my stored procedure code with a misspelled user defined function in it.
I noticed that at 1st time I execute the SP.
Is there any way to get a compile error when an SP include an invalid user-defined function name in it?
At compile time? No.
You can, however, use some of SQL's dependency objects (if using MS SQL) to find problems just after deployment, or as part of your beta testing. Aaron Bertran has a pretty nice article rounding up the options, depending upon the version of SQL Server.
Here is an example using SQL Server 2008 sys object called sql_expression_dependencies
CREATE FUNCTION dbo.scalarTest
(
#input1 INT,
#input2 INT
)
RETURNS INT
AS
BEGIN
-- Declare the return variable here
DECLARE #ResultVar int
-- Add the T-SQL statements to compute the return value here
SELECT #ResultVar = #input1 * #input2
-- Return the result of the function
RETURN #ResultVar
END
GO
--Fn Works!
SELECT dbo.ScalarTest(2,2)
GO
CREATE PROCEDURE dbo.procTest
AS
BEGIN
SELECT TOP 1 dbo.scalarTest(3, 3) as procResult
FROM sys.objects
END
GO
--Sproc Works!
EXEC dbo.procTest
GO
--Remove a dependency needed by our sproc
DROP FUNCTION dbo.scalarTest
GO
--Does anything have a broken dependency? YES
SELECT OBJECT_NAME(referencing_id) AS referencing_entity_name,
referenced_entity_name, *
FROM sys.sql_expression_dependencies
WHERE referenced_id IS NULL --dependency is missing
GO
--Does it work? No
EXEC dbo.procTest
GO
Though I have been using SQL Server, Oracle from last decade, I have been asked to
do some research on PostgreSQL and after some initial investigation it is evident that I am now stuck on retrieving data from the PostgreSQL database using Function.
Using following piece of code to retrieve the data and getting error
('ERROR [26000] ERROR: prepared statement "mytabletest" does not exist;
'Error while executing the query)
Code Snippets
Dim oDBCommand As DbCommand = GetDBCommand(oConnectionType, "mytabletest", CommandType.StoredProcedure)
Dim dstResults As DataSet = GetDataSet(ConnectionTypes.ODBC, oDBCommand)
Public Function GetDataReader(dbType As ConnectionTypes, command As DbCommand) As DbDataReader
Try
Dim oConnection As DbConnection = GetDBConnection(dbType)
Dim oDBTransaction As DbTransaction = oConnection.BeginTransaction
command.Connection = oConnection
command.Transaction = oDBTransaction
'GETTING ERROR ON FOLLOWING LINE
'ERROR [26000] ERROR: prepared statement "mytabletest" does not exist;
'Error while executing the query
return command.ExecuteReader()
Catch ex As Exception
Throw ex
Finally
End Try
Return Nothing
End Function
Environement I am currently working on is following:-
32 Bit Machine.
Visual Studio 2010 + SP1
ODBC Prodiver: PostgreSQL Unicode 9.01.02.00
ADO.Net (System.Data.Odbc)
Please note that I am open to any suggestions i.e. if I am completely doing it wrong
OR partially etc. Please feel free to write.
In order to make it easier for you to create a same environment, please use following table/function definition.
--- Simple table to make things easier to understand. <br>
CREATE TABLE mytable
(
messagetypeid integer NOT NULL,
messagetype character varying(100) NOT NULL
)
-- Function to retrieve data. <br>
CREATE OR REPLACE FUNCTION mytabletest() <br>
RETURNS SETOF refcursor AS $$
DECLARE
ref1 refcursor;
BEGIN
OPEN ref1 FOR SELECT * FROM mytable;
RETURN NEXT ref1;
END;
$$ LANGUAGE plpgsql;
Please Note:
If I use <br>
Dim oDBCommand As DbCommand = GetDBCommand(oConnectionType, "SELECT * FROM mytable", CommandType.Text)
then system manages to retrieve information from the datbase without any issue, however, as I mentioned as soon we use "Function" it throws an exception.
During my failed efforts to search any solution from the internet someone mentioned that Table should be created with the lower case it so just for the sake of it I recreated with the lower case, however, problem persists.
I am unfamiliar with .net but I suspect you meant something more like:
GetDBCommand(oConnectionType, "SELECT myfunc()", CommandType.Text)
Or in the case of SETOF functions etc..
GetDBCommand(oConnectionType, "SELECT * FROM myfunc()", CommandType.Text)
PostgreSQL does not have 'stored procedures' per-ce. It does have functions and I believe that the client/server protocol has a method for preparing statements that can then be executed multiple times with different variables (to save on the cost of parsing the SQL), but this should be exposed via your client library.