Re: [sqlite] Sqlite handler in trigger

[techi eth]

Thanks for clarification.

My understanding:

Process creating notified function has to create trigger & do the other
operation (Update, Insert and Delete) to get trigger logic execution. I
understand it may not be in same sequence.

Process can register function & create trigger, But trigger operation may
come on run time .(All by using common sqlite handler...)

>Which part of this sentence did you find unclear the first time round?

It is all clear

I was just checking for hint, if some one comes across to handle this kind
of scenario by using combination of sqlite capability & application logic!!!


On Fri, Sep 6, 2013 at 10:34 AM, Igor Tandetnik  wrote:

> On 9/6/2013 12:51 AM, techi eth wrote:
>
>> I am not sure if my problem I have stated clearly, found below detail
>> explanation!!!
>>
>> --**--**
>> 
>>
>> Process 1:
>>
>> Handler1 = OpenConn();
>>
>> Sqlite_Createfunc(Handler1, my_notifier_function()..);
>>
>> CREATE TRIGGER Event_test1 AFTER Update ON test BEGIN
>>
>> SELECT my_notifier_function();
>>
>> END;
>>
>> --**--**
>> 
>>
>> Proecss2:
>>
>> Handler2 = OpenConn();
>>
>> Update test SET value;
>>
>
> That last statement will fail with "unknown function
> 'my_notifier_function' " error.
>
>  In this scenario when proecss2 will do update...
>>
>
> In this scenario process2 will be unable to do update.
>
>
>  If above will not happen then please suggest what is best I can get from
>> sqlite3 to handle this kind of scenario.
>>
>
> Once again: there is no mechanism built into SQLite that would allow one
> process to be automatically notified that another process made a change to
> the database. Which part of this sentence did you find unclear the first
> time round?
>
> --
> Igor Tandetnik
>
> __**_
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Re: [sqlite] Sqlite handler in trigger

[Igor Tandetnik]

On 9/6/2013 12:51 AM, techi eth wrote:

I am not sure if my problem I have stated clearly, found below detail
explanation!!!



Process 1:

Handler1 = OpenConn();

Sqlite_Createfunc(Handler1, my_notifier_function()..);

CREATE TRIGGER Event_test1 AFTER Update ON test BEGIN

SELECT my_notifier_function();

END;



Proecss2:

Handler2 = OpenConn();

Update test SET value;


That last statement will fail with "unknown function 
'my_notifier_function' " error.



In this scenario when proecss2 will do update...


In this scenario process2 will be unable to do update.


If above will not happen then please suggest what is best I can get from
sqlite3 to handle this kind of scenario.


Once again: there is no mechanism built into SQLite that would allow one 
process to be automatically notified that another process made a change 
to the database. Which part of this sentence did you find unclear the 
first time round?

--
Igor Tandetnik

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Re: [sqlite] Sqlite handler in trigger

[techi eth]

I am not sure if my problem I have stated clearly, found below detail
explanation!!!



Process 1:

Handler1 = OpenConn();

Sqlite_Createfunc(Handler1, my_notifier_function()..);

CREATE TRIGGER Event_test1 AFTER Update ON test BEGIN

   SELECT my_notifier_function();

END;



Proecss2:

Handler2 = OpenConn();

Update test SET value;



In this scenario when proecss2 will do update then trigger logic will get
executed & my_notifier_function() function may get called.

If above will not happen then please suggest what is best I can get from
sqlite3 to handle this kind of scenario. May be any other possible
operation?

Thanks..



On Thu, Sep 5, 2013 at 6:55 PM, Igor Tandetnik  wrote:

> On 9/5/2013 5:39 AM, techi eth wrote:
>
>> I have case where one process is updating data with his private handler
>> but
>> trigger on update is created by other process by his private handler.
>>
>
> I'm not sure I understand this sentence. When you run CREATE TRIGGER
> statement, the trigger you've just created becomes part of the database
> schema, visible to all connections (unless you do CREATE TEMP TRIGGER; is
> this what you are talking about?)
>
> On the other hand, sqlite3_create_function() registers a custom function
> just for this connection. If you create a trigger that calls this function,
> then those connections where the function is not registered will fail to
> even prepare an UPDATE statement - SQLite will issue an "unknown function"
> error.
>
> In general, there is no mechanism built into SQLite that would allow one
> process to be automatically notified that another process made a change to
> the database. If that's what you want, you would have to implement that in
> your application - you can't somehow trick SQLite into doing it for you.
> --
> Igor Tandetnik
>
> __**_
> sqlite-users mailing list
> sqlite-users@sqlite.org
> http://sqlite.org:8080/cgi-**bin/mailman/listinfo/sqlite-**users
>
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Re: [sqlite] Sqlite handler in trigger

[Igor Tandetnik]

On 9/5/2013 5:39 AM, techi eth wrote:

I have case where one process is updating data with his private handler but
trigger on update is created by other process by his private handler.


I'm not sure I understand this sentence. When you run CREATE TRIGGER 
statement, the trigger you've just created becomes part of the database 
schema, visible to all connections (unless you do CREATE TEMP TRIGGER; 
is this what you are talking about?)


On the other hand, sqlite3_create_function() registers a custom function 
just for this connection. If you create a trigger that calls this 
function, then those connections where the function is not registered 
will fail to even prepare an UPDATE statement - SQLite will issue an 
"unknown function" error.


In general, there is no mechanism built into SQLite that would allow one 
process to be automatically notified that another process made a change 
to the database. If that's what you want, you would have to implement 
that in your application - you can't somehow trick SQLite into doing it 
for you.

--
Igor Tandetnik

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[sqlite] Sqlite handler in trigger

[techi eth]

Hi,

 I would like to check sqlite handler usability while using trigger:

I have register one function to sqlite by sqlite3_create_function().Now I
am creating trigger on update & selecting that function for callaback.

In above scenario it is mandatory that sqlite3 handler used while create
function & setting trigger should use for update.

I have case where one process is updating data with his private handler but
trigger on update is created by other process by his private handler.

Cheers -

Techi
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