I am trying to run the following do block script in sql through sqlx. As do block doesn't accept parameters, I tried to prepare it beforehand.
func LinkSessionUser(sessionId string, userId string, result *bool) error {
db := database.GetDB()
statement, err := db.Preparex(`
do
$$
begin
if (exists(select id from "session" where id = $1) and exists(select id from "user" where id = $2)) then
return insert into "session_user" (session_id, user_id) values ($1, $2) on conflict do nothing;
else
raise exception "Either session(id=%) or user(id=%) doesn't exist" $1, $2;
end if;
end
$$;
`)
if err != nil {
return err
}
return statement.Get(result, sessionId, userId)
}
But as I run it, I got the following errors:
sql: expected 0 arguments, got 2
How can I fix this issue? Should I be using Preparex to replace prepare in sql?
"Should I be using Preparex to replace prepare in sql?" -- Yes, however the problem you've encountered has nothing to do with Preparex, or the Go language itself, for that matter.
The code block of the DO command is a string literal, this string literal will not be, and has no reason to be, parsed during the PREPARE command execution, which is why the resulting prepared statement will have no defined parameters. As you correctly point out, DO does not support input parameters, but trying to get around that limitation by wrapping DO in a prepared statement will simply not produce the result you were hoping for.
If you need to conditionally execute parameterized SQL statements then you should use the CREATE FUNCTION command and explicitly execute the resulting function.
Related
I trying to select query based on condition using IF ElSE in postgres. Below is my query.
DO
$do$
DECLARE res varchar(50) := 'a';
BEGIN
IF (res = 'a') THEN
SELECT "Name" FROM "TestTable";
ELSE
SELECT "ID" FROM "TestTable";
END IF;
END
$do$
but I am getting following error
ERROR: query has no destination for result data
HINT: If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT: PL/pgSQL function inline_code_block line 5 at SQL statement
What I am doing wrong here??
DO purpose is to execute anonymous code block and it doesn't return anything (it returns void, to be specific).
You can execute your SELECT statement afterwards (outside of DO block), or perform an INSERT to temporary table which you need to create beforehand (and this can be done within the block).
I have a .sql script like this:
DO $$
DECLARE
prev_count := (SELECT count(*) FROM ...);
END$$;
UPDATE [...]
DO $$
DECLARE
cur_count := (SELECT count(*) FROM ...);
BEGIN
ASSERT cur_count = prev_count, 'Mismatch';
END$$;
In which I get some value, modify the database, and expect a new value to match an old value. However, I get errors like this:
psql:migration.sql:163: ERROR: column "prev_count" does not exist
LINE 1: SELECT cur_count = prev_count
^
QUERY: SELECT cur_count = prev_count
CONTEXT: PL/pgSQL function inline_code_block line 4 at ASSERT
I can't tell if this is a scoping issue because of the anonymous block, and why it's attempting to treat my variables like columns. Any ideas?
According to the manual DO executes an anonymous code block that:
... is treated as though it were the body of a function with no parameters, returning void. It is parsed and executed a single time...
So it is a function that returns VOID. In that sense prev_count only exists in the first DO.
To avoid this, you could create a TEMP table and insert the prev_count in the first DO so you can use it anywhere in the transaction.
I wrote a procedure STRING_SESTAVLJEN_ENAKOST_TABEL('MERILA_STRANKE') that generates part of code that i want to execute (some long if statement)
IF ((new.LOKACIJA IS DISTINCT FROM old.LOKACIJA )
OR (new.MODIFIED IS DISTINCT FROM old.MODIFIED )
OR (new.KARAKTERISTIKE IS DISTINCT FROM old.KARAKTERISTIKE )
OR (new.LETNIK IS DISTINCT FROM old.LETNIK )
OR (new.ID_PNS_CERT_POS IS DISTINCT FROM old.ID_PNS_CERT_POS )
OR (new.ID_PNS_CERT_POS IS DISTINCT FROM old.ID_PNS_CERT_POS ))
and I want to call it in trigger, then add some code and run it all together.
The code is:
SET TERM ^ ;
ALTER TRIGGER BI_MERILA_STRANKE ACTIVE
BEFORE INSERT OR UPDATE POSITION 0
AS
declare variable besedilo_primerjave varchar(5000);
BEGIN
begin
if (new.ID_MERILA_STRANKE is null OR new.ID_MERILA_STRANKE = 0) then new.ID_MERILA_STRANKE = gen_id(GEN_ID_MERILA_STRANKE,1);
end
begin
execute procedure STRING_SESTAVLJEN_ENAKOST_TABEL('MERILA_STRANKE')
returning_values :besedilo_primerjave;
execute statement besedilo_primerjave || ' THEN BEGIN INSERT INTO SYNC_INFO(TABLE_NAME,ID_COLUMN_NAME,ID_VALUE,DATETIME)
VALUES (
''MERILA_STRANKE'',
''ID_MERILA_STRANKE'',
NEW.ID_MERILA_STRANKE,
CURRENT_TIMESTAMP
);
END ELSE BEGIN
exception ENAK_RECORD;
END';
end
END^
SET TERM ; ^
Now when I run the update and trigger triggers I get this error:
SQL Message : -104 Invalid token
Engine Code : 335544569 Engine Message : Dynamic SQL Error SQL
error code = -104 Token unknown - line 1, column 1 IF
On the other hand if I write it like this:
SET TERM ^ ;
ALTER TRIGGER BI_MERILA_STRANKE ACTIVE
BEFORE INSERT OR UPDATE POSITION 0
AS
BEGIN
begin
if (new.ID_MERILA_STRANKE is null OR new.ID_MERILA_STRANKE = 0) then new.ID_MERILA_STRANKE = gen_id(GEN_ID_MERILA_STRANKE,1);
end
begin
IF ((new.LOKACIJA IS DISTINCT FROM old.LOKACIJA )
OR (new.MODIFIED IS DISTINCT FROM old.MODIFIED )
OR (new.KARAKTERISTIKE IS DISTINCT FROM old.KARAKTERISTIKE )
OR (new.LETNIK IS DISTINCT FROM old.LETNIK )
OR (new.ID_PNS_CERT_POS IS DISTINCT FROM old.ID_PNS_CERT_POS )
OR (new.ID_PNS_CERT_POS IS DISTINCT FROM old.ID_PNS_CERT_POS ))
THEN BEGIN
INSERT INTO SYNC_INFO(TABLE_NAME,ID_COLUMN_NAME,ID_VALUE,DATETIME)
VALUES (
'MERILA_STRANKE',
'ID_MERILA_STRANKE',
NEW.ID_MERILA_STRANKE,
CURRENT_TIMESTAMP
);
END ELSE BEGIN
exception ENAK_RECORD;
END
end
END^
SET TERM ; ^
It works as it should. I do not understand why it doesn't run if is more or less the same code.
As I also mentioned in your previous question, execute statement cannot be used to execute snippets of PSQL (procedural SQL) like that, it can only execute normal DSQL (dynamic SQL). And as it doesn't understand PSQL, you get the "token unknown - if" error, because if is not valid in DSQL.
execute statement is equivalent to executing SQL yourself from a query tool or application (it uses the same API), you can't use if there either.
There is a loophole by using an execute block statement, but that still would not allow you to gain access to the NEW (or OLD) trigger context variables unless explicitly passed as parameters, which would negate most of the usefulness of dynamically generated code in this context.
The only real solution is to write the trigger and not do it dynamically, maybe using a code generator (I'm not sure if any exist, otherwise you need to write that yourself).
I tried to run this script with the parameters in place but it keeps throwing syntax errors.Is there anything wrong with the syntax.Also what is the correct way to call this function.I require an output that tells me the update statement was executed successfully. I tried "select function_name(schema_name.TABLE_NAME);".Let me add that I am a beginner and am open to any kind of feedback. will also provide more details if necessary.
CREATE OR REPLACE FUNCTION function_name (TABLE_NAME IN character varying)
RETURNS text AS $SQLQuery$
DECLARE SQLQuery text;
BEGIN
SQLQuery =
' UPDATE '|| TABLE_NAME || ' SET column1=''0''
WHERE column1 is null;' ||
' UPDATE '|| TABLE_NAME || ' SET column2='value'
WHERE column2=''different value'';' ||
--multiple update statements later
Execute SQLQuery;
Return SQLQuery;
END;
$SQLQuery$
LANGUAGE plpgsql;
Update:
this is the error i am getting when i call the test function
ERROR: missing FROM-clause entry for table "schema_name"
LINE 2: select test_function(schema_name.TABLE_NAME);
^
********** Error **********
ERROR: missing FROM-clause entry for table "schema_name"
SQL state: 42P01
it is reading the function as a table?
I have also received syntax errors saying
EXECUTE column does not exist or that the function does not exist
even though i just declared it.
To use single quotes inside a siting constant, you must escape them by doubling them.
Instead of
' SET column1='0''
you'll have to write
' SET column1=''0'''
smth like:
CREATE OR REPLACE FUNCTION function_name (schema_name text,TABLE_NAME IN character varying)
RETURNS text AS $SQLQuery$
DECLARE
c int;
rtn text :='';
BEGIN
execute format(' UPDATE %I.%I SET column1=''0'' WHERE column1 is null;',schema_name,TABLE_NAME);
get diagnostics c = row_count;
raise info '%', 'affected: '||c;
rtn = rtn + 'affected: '||c||chr(10);
--repeat above construct for multiple update statement
return rtn;
END;
$SQLQuery$
LANGUAGE plpgsql;
and advises. I'm novice like you, but I learned to follow several rules, that help me:
with dynamic sql use format to avoid sql injection
don't overcomplicate things (eg the functionality you are looking for is inside UPDATE statement already - check the output. If you want to check the resulting row use, UPDATE ... RETURNING * construct.
practice is good, but reading concepts is precious.
In your POST select function_name(schema_name.TABLE_NAME); would not work, because you use schema_name.TABLE_NAME without quotes, but even if you put them, your function is vulnerable - what will happen if you run select function_name(';drop sometable;--');?..
You are trying to pass SQL Identifier, but your function takes string as parameter instead. You should change it to something like:
select test_function('schema_name.TABLE_NAME');
You can try that function below as base for whatever you are trying to do.
/* You need to split table and schema name
or you might get errors when using names that aren't lower case.
This: 'public.TEST1' would be translated to: "public.TEST1"
that is different table from public.test1
*/
CREATE OR REPLACE FUNCTION multi_update_stuff(schema_name varchar, table_name varchar)
/* We will return set of multiple columns. One possible method is to return table.
First column shows executed query, second if it returned no errors (true)
*/
RETURNS TABLE(SQLQuery text, result boolean)
AS $body$
DECLARE
/* Declare arroy of queries that we will iterate and execute later.
We use format() to build query from template and fill it with values.
%1$I can be described as "put first value here and treat it as object identifier"
%3$L can be described as "put third value here and treat it as SQL literal"
*/
SQLQueries text[] := array[
/* First query */
format('UPDATE %1$I.%2$I SET column1 = %3$L WHERE column1 is null;',
schema_name, table_name, '0'),
/* Second query */
format('UPDATE %1$I.%2$I SET column2 = %3$L WHERE column2 = %4$L;',
schema_name, table_name, 'value', 'different value'),
/* Third query, to see error free result */
'SELECT 1'];
BEGIN
/* Iterate our array */
FOREACH SQLQuery IN ARRAY SQLQueries
LOOP
/* Start transaction block */
BEGIN
EXECUTE SQLQuery;
result := true;
/* Catch error if any */
EXCEPTION
WHEN others THEN
result := false;
END;
/* Return row with whatever is assigned to variables listed in RETURNS.
In this case SQLQuery was already assigned by FOREACH.
*/
RETURN NEXT;
END LOOP;
END;
$body$
LANGUAGE plpgsql;
SELECT * FROM multi_update_stuff('schema_name', 'TABLE_NAME')
I am trying check if a value is null if so the select null else cast to numeric, but it throws an error. This is actually part of an insert statement
INSERT into someTable(name,created,power)
SELECT 'xyz',now(),
case when :power ='null' then NULL else cast(:power as numeric) end from abc
error that I get is
Error: ERROR: invalid input syntax for type numeric: "null"
:power is a variable that can be given any value using java code. If I give a value of null it give an error.
In code I get the following error from the java stack trace
org.postgresql.util.PSQLException: ERROR: cannot cast type bytea to numeric
Error:
SELECT CASE WHEN 'null' = 'null' THEN NULL ELSE cast('null' AS numeric) END
No error:
DO $$
DECLARE
power text := 'null';
BEGIN
PERFORM CASE WHEN power = 'null' THEN NULL ELSE cast(power AS numeric) END;
END;
$$
Explanation:
If you build a query string, the expression cast('null' AS numeric) or simply 'null'::numeric always raises an exception, even in an ELSE block that is never executed, because it is invalid input syntax and the exception is raised during the syntax check (like the error message implies), not during execution.
A CASE statement like you display only makes sense with a parameter or variable not with literals. The second instance of the literal has no connection to the first instance whatsoever after the query string has been assembled.
For dynamic SQL like that, you need to check the value before you build the query string. Or you use a function or prepared statement and pass the value as parameter. That would work, too.
More advice after comment:
In your particular case you could check the value in the app and build a query string like this:
INSERT INTO tbl(name, abc_id, created, power)
SELECT 'xyz'
, abc_id
, now()
, <insert_value_of_power_or_NULL_here> -- automatically converted to numeric
FROM abc
You may be interested in a different approach to INSERT data from a file conditionally.
Use COPY for files local to the server or psql's meta-command \copy for files local to the client.
if the field value is null, and you want in this case to map it to some value you can use coalesce(field_name, 'Some value') or coalesce(field_name, 123).
For full documentation see here.
You have to check with the IS operator, and not with the equal when you dealing with NULL :
INSERT into someTable(name,created,power)
SELECT 'xyz',now(),
case when :power IS null then NULL else cast(:power as numeric) end from abc
INSERT into someTable(name,created,power) SELECT 'xyz',now(),
case :power when 'null' then NULL else :power end::numeric from abc
I was trying to do something similar in order to update/insert some records where a numeric value can be null or not.
You can validate a variable before you send it to the function or inside the function depending the value passed
(For me using a variable is better than use CASE WHEN THEN ELSE END CASE every time you need to validate the value)
So to work with the NULL values using a regular comparison operand in order to find a record to update can be done by turning transform_null_equals to ON
I hope this help someone
CREATE OR REPLACE FUNCTION update_insert_transaction(vcodaccount integer, vcodaccountaux text,
vdescription text, vcodgroup integer)
RETURNS integer AS $$
DECLARE
n integer = 0;
vsql text = 'NULL';
BEGIN
IF vcodaccountaux <> '' THEN
vsql = vcodaccountaux;
END IF;
SET LOCAL transform_null_equals TO ON;
EXECUTE 'UPDATE account_import_conf SET (codaccount, codaccountaux, description, codgroup) =
('||vcodaccount||','||vsql||',trim('||quote_literal(vdescription)||'),'||vcodgroup||')
WHERE codaccount='||vcodaccount||' AND codaccountaux = '||vsql||' RETURNING * ';
GET DIAGNOSTICS n = ROW_COUNT;
IF n = 0 THEN
EXECUTE 'INSERT INTO account_import_conf (codaccount, codaccountaux, description, codgroup)
SELECT '||vcodaccount||','||vsql||' ,trim('||quote_literal(vdescription)||'),'||vcodgroup||';';
END IF;
RETURN n;
END;$$
LANGUAGE plpgsql;