I have a trigger ON UPDATE on a table that calls a custom function. In the custom function, I want to insert into a log table the name of the current SAVEPOINT (the deepest unsaved one) along with the name of the table and the timestamp. I am currently hardcoding the name of the table (please let me know if there is a better way) but I cannot figure out how to get the name of the current SAVEPOINT.
Thanks!
By default, SQLite has no functions to get the current savepoint (or the current trigger's table).
However, if you have compiled SQLite into your application, you could use sqliteInt.h, and, from a variable sqlite3 *db, access the current savepoint's name as db->pSavepoint->zName.
One way to determine current save point, without resorting to using sqlite3int.h and the sqlite3* db structure is to set up a compile time authorization callback (http://www.sqlite.org/c3ref/set_authorizer.html) and then look for an action code (http://www.sqlite.org/c3ref/c_alter_table.html) of SQLITE_SAVEPOINT.
The fourth parameter passed to the authorizer callback will be the name of a savepoint. By storing this name in your structure - you will have access to the name of the last save point passed in during analysis/preparation of your sqlite3_stmt.
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I have a scenario like we need to load data from source file to target table from a particular date [like LOAD_DATE], So I’ll create a mapping parameter for LOAD_DATE and pass that in Source Qualifier query. My query looks like this.
SELECT * FROM my_TABLE where DATE >= ‘$$LOAD_DATE’
So here I need to pass parameter values for ‘$$LOAD_DATE’ from another external database. I know that I need to pass the values from the Parameter file.
But my requirement is not to hardcore the values in the Parameter file but to feed it in runtime from another database. I will appreciate your help and thoughts on this.
You dont have to hardcode.
You can do it like this -
option 1. Create a mapping to create the param file in particular format.
Read for the other DB.
In expression transformation create below port which will generate actual param string. Pls note, we need to add new line so its recognized like a actual param file.
out_str = '[<<name of folder . name of workflow or sessoin>>]' || chr(12) ||
'$$LOAD_DATE='|||| CHR(39) ||<<date value from another DB>>|| CHR(39)
Then link above port to a flat file target. Name the output file as session_param.txt or whatever suitable. Pls make sure the parameter is generated correctly.
Use above file as a parameter file in your actual workflow.
Option 2 - You can join another table with original table flow. This can be difficult and need to change existing mapping.
Join the another table from another DB with main table based on a dummy condition. make sure you get distinct values of LOAD_DATE from another table. Make sure you always have 1 value from this DB.
Once you have the LOAD_DATE field from another table, you can use it in filter transformation to filter the data.
After this point you can add your original mapping.
Whole mapping should be like this-
SQ_MAIN_TABLE ----------------------->|
sq_ANOTHER_TABLE --DISTINCT_LOAD_DT-->JNR--FIL on LOAD_DT --><<your mapping logic>>
I have an Ionic App using SQLite. I don't have any problems with implementation.
The issue is that I need to import an SQL file using SQLitePorter to populate the database with configuration info.
But also, on the same database I have user info, so my question is:
Everytime I start the app, it will import the sql file, fill the database and probably overwrite my user data too? Since it is all on the same base?
I assume that you can always init your table using string queries inside your code. The problem is not that you are importing a .sql file. Right?
According to https://www.sqlitetutorial.net/sqlite-create-table/ it is obvious that you always create a table with [IF NOT EXISTS] switch. Writing a query like :
CREATE TABLE [IF NOT EXISTS] [schema_name].table_name (
column_1 data_type PRIMARY KEY);
you let sqlite to decide if it's going to create a table with the risk to overwrite an existing table. It is supposed that you can trust that sqlite is smart enough, not to overwrite any information especially if you use 'BEGIN TRANSACTION' - 'COMMIT' procedure.
I give my answer assuming that you have imported data and user data in distinct tables, so you can manipulate what you populate and what you don't. Is that right?
What I usually do, is to have a sql file like this:
DROP TABLE configutation_a;
DROP TABLE configutation_b;
CREATE TABLE configutation_a;
INSERT INTO configutation_a (...);
CREATE TABLE configutation_b;
INSERT INTO configutation_b (...);
CREATE TABLE IF NOT EXIST user_data (...);
This means that every time the app starts, I am updating with the configuration data I have at that time (that's is why we use http.get to get any configuration file from a remote repo in the future) and create user data only if user_data table is not there (hopefully initial start).
Conclusion: It's always a good practice, in my opinion, to trust a database product 100% and abstractly let it do any transaction that might give you some risk if you implemented your self in your code; since it gives a tool for that.For example, the keyword [if not exists], is always safer than implementing a table checker your self.
I hope that helps.
PS: In case you refer in create database procedure, SQLite, connects to a database file and it doesn't exist, it creates it. For someone comfortable in sqlite command line, when you type
sqlite3 /home/user/db/configuration.db will connect you with this db and if the file is not there, it will create it.
I am aware of some ways for seeing the recent queries for the current database, such as:
SELECT deqs.last_execution_time AS [Time], dest.text AS [Query], dest.*
FROM sys.dm_exec_query_stats AS deqs
CROSS APPLY sys.dm_exec_sql_text(deqs.sql_handle) AS dest
WHERE dest.dbid = DB_ID()
ORDER BY deqs.last_execution_time DESC
My problem is that the results aren't showing the values being passed to the PROC, but are instead showing the names of the parameters. I already know the name of the PROC and I have the script. I need to know what a particular ASP app is passing in.
For now I just have the PROC INSERTing the param values into a logging table, but I was wondering if there was a better way.
Try to use custom logging in the stored procedure. Whenever the stored procedure is invoked, log an entry into the log table with the passed in params.
I need to parameterize a view, and I am doing so by creating a TEMP TABLE which has the parameters for the view.
CREATE TEMP TABLE parms (parm1 INTEGER, parm2 INTEGER);
CREATE VIEW tableview AS ...
The VIEW is rather complex, but it basically uses these two parameters to kick start a recursive CTE, and there isn't any other way that I have found to express the view without these parameters.
The parameters must be stored in a temporary table because each connection should be able to have its own view with different parameters.
In any case, this works fine for creating the view itself, so long as I create the same TEMP TABLE at the start of any queries that use the view, e.g.:
CREATE TEMP TABLE parms (parm1 INTEGER, parm2 INTEGER);
INSERT INTO parms (parm1,parm2) VALUES (5,66);
SELECT * FROM tableview;
I am able to do the same thing to create a trigger to allow inserts on the view:
CREATE TEMP TABLE parms (parm1 INTEGER, parm2 INTEGER);
CREATE TRIGGER tableinsert INSTEAD OF INSERT ON tableview ...
However, when I try to do an actual INSERT (re-creating the TEMP TABLE first as before) I get an error:
no such table: main.parms
If I create a non-temporary table, I do not get this error, but then I have the problem that different connections can't have their own separate views.
I have review the documentation for triggers, and it mentions caveats of using temporary triggers on a non-temporary table, but I don't see anything regarding the reverse.
I did find a reference elsewhere that indicated that "the table... must exist in the same database as the table or view to which the trigger is attached". I thought a temporary table was part of the current database, is this not true? Is there some way to make this true?
I also tried accessing the parms table as temp.parms in the TRIGGER, but got the error:
qualified table names are not allowed on INSERT, UPDATE, and DELETE
statements within triggers
If I can't use a temporary table, is there some way to work around it to accomplish the same thing?
Update: Ok, so it seems to be an SQLite limitation. After digging around a bit in the SQLite source code, it seems to be pretty trivial to allow SELECT access to a temporary table in a trigger. However, allowing UPDATE access appears to be a lot harder.
Temporary objects are created in a separate database named temp, so they are not accessible from triggers in other databases.
The remaining mechanism to get a connection-specific value into a trigger is to use a user-defined function.
SQLite allows to define custom functions that can be called from SQL statements. I use this to get notified of trigger activity in my application:
CREATE TRIGGER AfterInsert AFTER INSERT ON T
BEGIN
-- main trigger code involves some extra db modifications
-- ...
-- invoke application callback
SELECT ChangeNotify('T', 'INSERT', NEW.id);
END;
However, user-defined functions are added only to current database connection. There may be other clients who haven't defined ChangeNotify and I don't want them to get a "no such function" error.
Is is possible to call a function only if it's defined? Any alternative solution is also appreciated.
SQLite is designed as an embedded database, so it is assumed that your application controls what is done with the database.
SQLite has no SQL function to check for user-defined functions.
If you want to detect changes made only from your own program, use sqlite3_update_hook.
Prior to calling your user defined function, you can check if the function exists by selecting from pragma_function_list;
select exists(select 1 from pragma_function_list where name='ChangeNotify');
1
It would be possible by combining a query against pragma_function_list and a WHEN statement on the trigger --
CREATE TRIGGER AfterInsert AFTER INSERT ON T
WHEN EXISTS (SELECT 1 FROM pragma_function_list WHERE name = 'ChangeNotify')
BEGIN
SELECT ChangeNotify('T', 'INSERT', NEW.id);
END;
except that query preparation attempts to resolve functions prior to execution. So, afaik, this isn't possible to do in a trigger.
I need to do the same thing and asked here: https://sqlite.org/forum/forumpost/a997b1a01d
Hopefully they come back with a solution.
Update
SQLite forum suggestion is to use create temp trigger when your extension loads -- https://sqlite.org/forum/forumpost/96160a6536e33f71
This is actually a great solution as temp triggers are:
not visible to other connections
are cleaned up when the connection creating them ends