I am writing in an RMD code as follows:
$$
\text{We start with the following equation}\\
\mu=\lambda*\theta^E*PT\\
\text{The following represents a model for lambda within the context of our question}\\
\lambda=\lambda_0*\theta_1^M*\theta_2^{M_75}*\theta_3^{M_80}*\theta_4^{M_85}*\theta_5^{M2000}*\theta_6^{M2005}*PT\\
\log(\lambda)=log(\lambda_0)+log(\theta_1)*M+log(\theta_2)*M75+log(\theta_3)*M80+log(\theta_4)*M85+log(\theta_5)*M2000+log(\theta_6)*M2005+log(PT)\\
$$
In my R studio, I am getting the expected output:
.
However, when I knit my file to HTML, I get an unexpected output:
.
Does anyone know what's going on here?
You should do this:
$\text{We start with the following equation}\\$
$$\mu=\lambda*\theta^E*PT\\$$
$\text{The following represents a model for lambda within the context of our question}\\$
$$\lambda=\lambda_0*\theta_1^M*\theta_2^{M_75}*\theta_3^{M_80}*\theta_4^{M_85}*\theta_5^{M2000}*\theta_6^{M2005}*PT\\$$
$\text{My big equation}\\$
$$\log(\lambda)=log(\lambda_0)+log(\theta_1)*M+log(\theta_2)*M75+log(\theta_3)*M80+log(\theta_4)*M85+log(\theta_5)*M2000+log(\theta_6)*M2005+log(PT)\\$$
$ - inline formula, $$ - "centered" formula
Related
I'm trying to create this trigger in my PostgresSql environment:
CREATE TRIGGER MYTRIGGER
BEFORE INSERT
ON MYTABLE
FOR EACH ROW
BEGIN
IF( LENGTH( :NEW.VAL ) > 10 )
THEN
RAISE_APPLICATION_ERROR( -20003,
'Cannot exceed 10 chars' );
END IF;
IF :NEW.FQN_ID IS NULL THEN
:NEW.FQN_ID :=
CASE :NEW.SUBTYPECODE
WHEN NULL THEN 'A:'
WHEN 0 THEN 'B:'
WHEN 1 THEN 'C:'
WHEN 2 THEN 'D:'
ELSE 'Z:' || :NEW.SUBTYPECODE || '::'
--END || :NEW.OBJECTID;
END || STRUCTURE_FQNID_SEQ.NEXTVAL;
END IF;
END;
But I get this error:
ERROR: syntax error at or near "BEGIN"
LINE 5: BEGIN
^
SQL state: 42601
Character: 79
I think I'm missing something but I can't get it.
Any suggestion would be greatly appreciated.
Thank you.
Here are my notes about triggers in several DBMSs: https://github.com/iwis/SQL-notes. I marked the differences between the DBMSs in orange. I think that the notes are quite complete, so you don't have to read about triggers in Postgres documentation.
I see the following changes that need to done in your example:
Change Oracle :NEW to Postgres NEW.
Instead of a BEGIN ... END block, write EXECUTE FUNCTION my_trigger_function();, where my_trigger_function is a function that needs to be created like in the example given by a_horse_with_no_name.
This function should return NEW in your case - the reason is described here.
If a more complicated code is fired by a trigger, then you also need to understand the differences between PL/SQL and PL/pgSQL languages. These languages are quite similar, though there are some differences. Your code is simple so the differences are small. It's probably enough to:
Write Postgres RETURNS in the function definition instead of Oracle RETURN.
Write $$ before BEGIN, and $$ LANGUAGE plpgsql; after END.
Write Postgres RAISE 'Cannot exceed 10 chars'; instead of Oracle RAISE_APPLICATION_ERROR(-20003, 'Cannot exceed 10 chars');.
I don't know if sequences work in the same way in PostgreSQL - I haven't read about them yet.
Let me know if my notes are understandable - I'm not sure about it because they are super compact so you need to decipher the markings used by me.
I am struggling to figure out how to best handle the return of results or errors to my application from Postgres stored functions.
Consider the following contrived psudeocode example:
app.get_resource(_username text)
RETURNS <???>
BEGIN
IF ([ ..user exists.. ] = FALSE) THEN
RETURN 'ERR_USER_NOT_FOUND';
END IF;
IF ([ ..user has permission.. ] = FALSE) THEN
RETURN 'ERR_NO_PERMISSION';
END IF;
-- Return the full user object.
RETURN QUERY( SELECT 1
FROM app.resources
WHERE app.resources.owner = _username);
END
The function can fail with a specific error or succeed and return 0 or more resources.
At first I tried creating a custom type to always use as a standard return type in eachh function:
CREATE TYPE app.appresult AS (
success boolean,
error text,
result anyelement
);
Postgres does not allow this however:
[42P16] ERROR: column "result" has pseudo-type anyelement
I then discovered OUT parameters and attempted the following uses:
CREATE OR REPLACE FUNCTION app.get_resource(
IN _username text,
OUT _result app.appresult -- Custom type
-- {success bool, error text}
)
RETURNS SETOF record
AS
$$
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 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();
I'm unable to get a simple SQL function that run over rows of a tables and display it column info
Here how the SQL function looks like.
CREATE OR REPLACE FUNCTION iterators() RETURNS Void AS $$
DECLARE
t2_row call_records%ROWTYPE;
BEGIN
FOR t2_row IN (SELECT timestamp,plain_crn INTO call_records limit 2)
LOOP
RAISE NOTICE t2_row.timestamp;
END LOOP
END
$$ LANGUAGE plpgsql;
But I keep getting following error
ERROR: syntax error at or near "t2_row"
LINE 7: RAISE NOTICE t2_row.timestamp;
I'm not sure what possible syntax error the code has? Is it possible to get a bit more verbose error log or know as to what is the syntax error in code that I have to fix.
Statement RAISE requires format string. It should be trivial, but should be there.
RAISE NOTICE '%', t2_row.timestamp;
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.