Use case:
Application requires a subset of attributes, based on business rules
Example:
Some students do not require to enter in home address
Database : Oracle
Proposed implementation:
Build json object containing all possible attribute named pairs, then selectively remove specific named pairs
Issue:
Hoped to use native oracle function to remove the specified named pair.
e.g json_object.remove_attribute('home_address');
However Oracle do not appear to provide any such method.
Workaround : Convert json_object to VARCHAR2 string, and then use combination of INSTR and REPLACE to remove named pair.
Illustrative code:
DECLARE
CURSOR cur_student_json (p_s_ref IN VARCHAR2) IS
SELECT JSON_OBJECT(
,'s_surname' value s.s_surname
,'s_forename_1' value s.s_forename_1
,'s_home_address_1' value s.s_home_address_1
RETURNING VARCHAR2 ) student_json
FROM students s
WHERE s.s_ref = p_s_ref;
BEGIN
FOR x IN cur_student_json (p_s_ref) LOOP
vs_student_json:=x.student_json;
EXIT;
END LOOP;
-- Determine student type
vs_student_type:=get_student_type(p_s_ref);
-- Collect list of elements not required, based on student type
FOR x IN cur_json_inorout(vs_student_type) LOOP
-- Remove element from the json
vs_student_json:=json_remove(vs_student_json,x.attribute);
END LOOP;
END;
/
Question:
There must be an elegant method to achieve requirement
Classify under RTFM. Needs Oracle 12.2
DECLARE
-- Declare an object of type JSON_OBJECT_T
l_obj JSON_OBJECT_T;
-- Declare cursor to build json object
CURSOR cur_student_json (p_s_ref IN VARCHAR2) IS
SELECT JSON_OBJECT(
,'s_surname' value s.s_surname
,'s_forename_1' value s.s_forename_1
,'s_home_address_1' value s.s_home_address_1
) student_json
FROM students s
WHERE s.s_ref = p_s_ref;
BEGIN
-- Initialise object
l_obj := JSON_OBJECT_T();
-- Populate the object
FOR x IN cur_student_json (p_s_ref) LOOP
l_obj:=JSON_OBJECT_T.parse(x.student_json);
EXIT;
END LOOP;
-- Determine student type
vs_student_type:=get_student_type(p_s_ref);
-- Collect list of elements not required, based on student type
FOR x IN cur_json_inorout(vs_student_type) LOOP
-- Remove element from the json
l_obj.remove(x.attribute);
END LOOP;
-- Display modified object
dbms_output.put_line(l_obj.stringify);
END;
/
Related
I try to do as explained in:
https://wiki.postgresql.org/wiki/Audit_trigger
Auditing values as JSON
For PostgreSQL 9.2, or 9.1 with the fantastic json_91 addon, you can
log the old and new values in the table as structured json instead of
flat text, giving you much more power to query your audit history.
Just change the types of v_old_data, v_new_data, original_data and
new_data from TEXT to json, then replace ROW(OLD.) and ROW(NEW.)
with row_to_json(OLD) and row_to_json(NEW) respectively.
However this get me a error:
CREATE OR REPLACE FUNCTION add_log (name text, Action TEXT, data jsonb, OUT RETURNS BOOLEAN)
AS $$
BEGIN
RETURNS = true;
END;
$$
LANGUAGE 'plpgsql';
CREATE OR REPLACE FUNCTION log_city() RETURNS TRIGGER AS
$$
DECLARE
v_new_data jsonb;
BEGIN
IF (TG_OP = 'UPDATE') THEN
RETURN NEW;
ELSIF (TG_OP = 'INSERT') THEN
v_new_data := row_to_jsonb(NEW);
EXECUTE add_log('City', 'City.New', v_new_data);
RETURN NEW;
END IF;
RETURN NULL; -- result is ignored since this is an AFTER trigger
END;
$$ LANGUAGE plpgsql;
INSERT INTO Location (city, state, country) values ('a', 'b' , 'c')
It say:
ERROR: function row_to_jsonb(location) does not exist
If I put v_new_data := row_to_jsonb(ROW(NEW)); then I get:
ERROR: function row_to_jsonb(record) does not exist
It's stated in the documentation that
Table 9-42 shows the functions that are available for creating json
and jsonb values. (There are no equivalent functions for jsonb, of the
row_to_json and array_to_json functions. However, the to_jsonb
function supplies much the same functionality as these functions
would.)
thus it's row_to_json that has to be used. a row_to_jsonb does not exists but row_to_json produces the desired result for the JSONB type as well.
i'm trying once again to work with postgres 9.4 and the new json functionalities and might have encountered a bug. The Problem is that once i have generated a json-string via to_json(..) i cant transform it back to an Composite type because postgres cant handle the json-array inside.
When i write it in postgres Notation it works and i can even access all the fields inside the Array.
Does anyone knows a better workarround?
Example 1: composite type to json and back
DROP TYPE IF EXISTS myType;
CREATE TYPE myType AS (
since TIMESTAMP,
words TEXT[]
);
DO $$
DECLARE
_my_variable myType;
_my_json JSON;
BEGIN
_my_variable := ROW(now(),ARRAY['Here','is','a','List','of','Words']);
_my_json := to_json(_my_variable);
RAISE INFO 'how my json looks like: %', _my_json;
--{"since":"2015-06-30T09:12:35.12346","word":["Here","is","a","List","of","Words"]}
_my_variable := json_populate_record(NULL::myType,_my_json);
--ERROR: malformed array literal: "["Here","is","a","List","of","Words"]"
--DETAIL: "[" must introduce explicitly-specified array dimensions.
--CONTEXT: PL/pgSQL function inline_code_block line 13 at assignment
END $$;
Example 2: json with postgres-notation like array to composite type
DO $$
DECLARE
_my_variable myType;
_my_json JSON;
BEGIN
_my_json := '{"since":"2015-06-30T09:12:35.12346","words": "{Here,is,a,List,of,Words}" }';
_my_variable := json_populate_record(NULL::myType,_my_json);
RAISE INFO 'how my object looks like: %', _my_variable;
RAISE INFO 'how my array looks like: %', _my_variable.words;
--("2015-06-30 09:12:35.12346","{Here,is,a,List,of,Words}")
END $$;
I'm new with PL/SQL I have a assignment where I need to make a function. The assignment is as follows:
> "Create a function 'afdeling_van:'
> - this function accepts a medewerkernummer(employee number) as argument
> - give the afdelingnummer(department number) from the medewerkernummer(employee number) back"
So I need to create a function with a parameter that returns a number. After that I probably need to add some code to make it return a medewerker(employee) number back.
I got pretty stuck with this one as I am really new to PL/SQL. What I do have at the moment is this:
declare
procedure afdeling_van(p_persoon in medewerkers.mnr%type)--table name with column name
is
begin
select med.mnr
from medewerkers med;
where mnr = p_persoon;
end afdeling_van;
begin
afdeling_van(10);
end;
It's not working for me. I have tried different solutions. But as I lack experience and I cannot find the solution or information that I need on the web. I am trying it to ask here
one other thing. I think it's similair to my problem. In the previous assignment I made a procedure instead of a function. The procedure is as follows:
declare
v_medewerker varchar2(50) := ontsla_med();
procedure ontsla_med(p_medewerkers in medewerkers.naam%type)
is
begin
delete from medewerkers
where naam = p_medewerkers;
end ontsla_med;
begin
ontsla_med('');
dbms_output.put_line('Medewerker: ' || v_medewerker || 'verwijdert uit medewerker, inschrijven en uitvoeringen bestand.' );
exception
when no_data_found then
dbms_output.put_line('Medewerker bestaat niet/ is al verwijderd.');
end;
/
this works except for the last dbms_output.put_line. If I remove the output line, then it will work and with the output line, it won't.
I hope my question is not too vague.
Thanks in advance.
You need to create a function instead of a procedure, and you've got a semi-colon in the wrong place. Try something like:
declare
nReturned_value MEDEWERKERS.AFDELINGNUMMER%TYPE;
FUNCTION afdeling_van(p_persoon in medewerkers.mnr%type) --table name with column name
RETURN MEDEWERKERS.AFDELINGNUMMER%TYPE
is
nAFDELINGNUMMER MEDEWERKERS.AFDELINGNUMMER%TYPE;
begin
select med.AFDELINGNUMMER
INTO nAFDELINGNUMMER
from medewerkers med
where mnr = p_persoon;
RETURN nAFDELINGNUMMER ;
end afdeling_van;
begin
nReturned_value := afdeling_van(10);
DBMS_OUTPUT.PUT_LINE('nReturned_value = ' || nReturned_value);
end;
Edit
In your second example, I don't believe that the line v_medewerker varchar2(50) := ontsla_med(); will compile. ontsla_med is a procedure rather than a function, and because procedures don't return anything they can't be used in an assignment statement.
However, v_medewerker is only used in the DBMS_OUTPUT line which you say causes a problem - thus, it may be that the compiler is eliminating the variable because it's not used if the DBMS_OUTPUT line is removed, thus eliminating the problem. Try changing the declaration to v_medwerker varchar2(50) := 'Hello'; and see if that helps.
I'm migrating mysql database to postgres and ran into a roadblock regarding some basic xml functionality. In MySql I had stored procedures which would replace nodes inside xml document but cannot find any way to do so in postgres.
Here's my stored proc from mysql:
CREATE DEFINER=`root`#`localhost` PROCEDURE `SP_UpdateExamFilesXmlNode`(examFileId int, xPathExpression varchar(128), xmlNode longtext)
BEGIN
DECLARE xmlData longtext;
DECLARE newXmlData longtext;
DECLARE xmlNodeCount int;
SET xmlData = NULL;
SELECT xml_data INTO xmlData FROM sonixhub.exam_files WHERE id = examFileId;
IF xmlData IS NOT NULL THEN
-- check if the node already exists and if it does then simply update it
SET xmlNodeCount = ExtractValue(xmlData, CONCAT('count(',xPathExpression,')'));
IF xmlNodeCount > 0 THEN
SET newXmlData = UpdateXML(xmlData, xPathExpression, xmlNode);
-- if node doesn't exist then we have to add it manually
ELSE
SET newXmlData = REPLACE(xmlData, '</ImageXmlData>', CONCAT(xmlNode, '</ImageXmlData>'));
END IF;
UPDATE sonixhub.exam_files SET xml_data = newXmlData WHERE id = examFileId;
ELSE
-- there is no xml found so create xml from scratch and insert the node
SET xmlData = CONCAT('<ImageXmlData>',xmlNode,'</ImageXmlData>');
UPDATE sonixhub.exam_files SET xml_data = xmlData WHERE id = examFileId;
END IF;
END
Is there any way to replicate this functionality in postgres function instead of moving the logic into the application itself?
EDIT - FOUND A SOLUTION TO MY PROBLEM
I found a solution using mix of postgres xml and string formatting functions.
examFileId is used to find the row to be updated with the xml, change the code with your table info
is the hardcoded root node in my case, but you can change it to whatever you like.
Here's how you call the function:
-- this adds <DicomTags> node to your xml value in the table, if <DicomTags> already exists then it's replaced by the one passed in
select update_exam_files_xml_node(1, '/ImageXmlData/DicomTags', '<DicomTags><DicomTag>xxx</DicomTag></DicomTags>');
-- this adds <Settings> node to your xml value in the table, if <Settings> already exists then it's replaced by the one passed in
select update_exam_files_xml_node(1, '/ImageXmlData/Settings', '<Settings>asdf</Settings>');
CREATE OR REPLACE FUNCTION update_exam_files_xml_node(examFileId int, xPathExpression text, xmlNode text)
RETURNS void AS
$BODY$
DECLARE xmlData xml;
DECLARE newXmlData xml;
DECLARE xmlNodeCount int;
DECLARE replaceTag text;
BEGIN
SELECT xml_data INTO xmlData FROM exam_files WHERE id = examFileId;
IF xml_is_well_formed(xmlNode) = false THEN
PERFORM add_error_log('update_exam_files_xml_node', 'xmlNode is not well formed xml');
RETURN;
END IF;
IF xmlData IS NOT NULL THEN
-- check if the node already exists and if it does then simply update it
IF xmlexists(xPathExpression PASSING BY REF xml(xmlData)) = true THEN
-- get the node name
replaceTag := regexp_replace(xPathExpression, '/.*/', '');
-- replace the existing node with the newly passed in node
newXmlData := xml(regexp_replace(xmlData::text, '<'||replaceTag||'>.*</'||replaceTag||'>', xmlNode));
-- if node doesn't exist then we have to add it manually
ELSE
newXmlData := xml(REPLACE(xmlData::text, '</ImageXmlData>', xmlNode||'</ImageXmlData>'));
END IF;
UPDATE exam_files SET xml_data = newXmlData WHERE id = examFileId;
ELSE
-- there is no xml found so create xml from scratch and insert the node
xmlData := '<ImageXmlData>'||xmlNode||'</ImageXmlData>';
UPDATE exam_files SET xml_data = xmlData WHERE id = examFileId;
END IF;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
Glad you got a solution. To be honest, string formatting functions tend to be a bit difficult to reliably use inside SGML due to issues relating to hierarchies of languages. I.e. regexps have hard limits as to what they can do.
A better solution is likely to be to go a very different direction and write your functions in PL/PerlU or PL/Python, and use existing XML processing capabilities for those languages. This is likely to give you a better and more robust solution.
I keep getting a error when i run this code, What wrong with the code?
create or replace function f_vars(line varchar2,delimit varchar2 default ',')
return line_type is type line_type is varray(1000) of varchar2(3000);
sline varchar2 (3000);
line_var line_type;
pos number;
begin
sline := line;
for i in 1 .. lenght(sline)
loop
pos := instr(sline,delimit,1,1);
if pos =0 then
line_var(i):=sline;
exit;
endif;
string:=substr(sline,1,pos-1);
line_var(i):=string;
sline := substr(sline,pos+1,length(sline));
end loop;
return line_var;
end;
LINE/COL ERROR
20/5 PLS-00103: Encountered the symbol "LOOP" when expecting one of
the following:
if
22/4 PLS-00103: Encountered the symbol "end-of-file" when expecting
one of the following:
end not pragma final instantiable order overriding static
member constructor map
Stack Overflow isn't really a de-bugging service.
However, I'm feeling generous.
You have spelt length incorrectly; correcting this should fix your first error. Your second is caused by endif;, no space, which means that the if statement has no terminator.
This will not correct all your errors. For instance, you're assigning something to the undefined (and unnecessary) variable string.
I do have more to say though...
I cannot over-emphasise the importance of code-style and whitespace. Your code is fairly unreadable. While this may not matter to you now it will matter to someone else coming to the code in 6 months time. It will probably matter to you in 6 months time when you're trying to work out what you wrote.
Secondly, I cannot over-emphasise the importance of comments. For exactly the same reasons as whitespace, comments are a very important part of understanding how something works.
Thirdly, always explicitly name your function when ending it. It makes things a lot clearer in packages so it's a good habit to have and in functions it'll help with matching up the end problem that caused your second error.
Lastly, if you want to return the user-defined type line_type you need to declare this _outside your function. Something like the following:
create or replace object t_line_type as object ( a varchar2(3000));
create or replace type line_type as varray(1000) of t_line_type;
Adding whitespace your function might look something like the following. This is my coding style and I'm definitely not suggesting that you should slavishly follow it but it helps to have some standardisation.
create or replace function f_vars ( PLine in varchar2
, PDelimiter in varchar2 default ','
) return line_type is
/* This function takes in a line and a delimiter, splits
it on the delimiter and returns it in a varray.
*/
-- local variables are l_
l_line varchar2 (3000) := PLine;
l_pos number;
-- user defined types are t_
-- This is a varray.
t_line line_type;
begin
for i in 1 .. length(l_line) loop
-- Get the position of the first delimiter.
l_pos := instr(l_line, PDelimiter, 1, 1);
-- Exit when we have run out of delimiters.
if l_pos = 0 then
t_line_var(i) := l_line;
exit;
end if;
-- Fill in the varray and take the part of a string
-- between our previous delimiter and the next.
t_line_var(i) := substr(l_line, 1, l_pos - 1);
l_line := substr(l_line, l_pos + 1, length(l_line));
end loop;
return t_line;
end f_vars;
/