Re: [sqlite] SELECT ... FOR UPDATE

[Hick Gunter]

SQLite does not use row level locking, only file level locking. You can use 
BEGIN IMMEDIATE to exclude writers or BEGIN EXCLUSIVE to exclude readers and 
writers. If you do not explicitly start a transaction, each statement 
constitutes it's own transaction.

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Von: sqlite-users-boun...@mailinglists.sqlite.org 
[mailto:sqlite-users-boun...@mailinglists.sqlite.org] Im Auftrag von Scott 
Doctor
Gesendet: Dienstag, 24. Mai 2016 19:34
An: sqlite-users@mailinglists.sqlite.org
Betreff: [sqlite] SELECT ... FOR UPDATE

My current project has me bouncing between sqlite and mysql. In mysql, to lock 
a row of data at the start of a process to hold off concurrent operations, the 
recommended technique with the innodb engine is to issue

SELECT field FROM table FOR UPDATE;

This holds off any other process from accessing that row until it is released. 
This is according to the mysql manual.

My question is, looking through the sqlite documentation, it is not clear how 
sqlite will handle that statement. Since I am porting sql between several 
databases, I am trying to figure out if I need to search and destroy any of 
those statements from mysql when converting it to sqlite.


Scott Doctor
sc...@scottdoctor.com
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Re: [sqlite] SELECT ... FOR UPDATE

[Simon Slavin]

On 24 May 2016, at 8:04pm, Igor Tandetnik  wrote:

> SQLite will report a syntax error. That's pretty easy to confirm 
> experimentally.

Download the command line shell tool as a "precompiled binary" for your 
platform:



and test commands to your heart's content:



Simon.
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Re: [sqlite] SELECT ... FOR UPDATE

[Igor Tandetnik]

On 5/24/2016 1:34 PM, Scott Doctor wrote:

SELECT field FROM table FOR UPDATE;

My question is, looking through the sqlite documentation, it is not
clear how sqlite will handle that statement.


SQLite will report a syntax error. That's pretty easy to confirm 
experimentally.

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Igor Tandetnik

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[sqlite] SELECT ... FOR UPDATE

[Scott Doctor]

My current project has me bouncing between sqlite and mysql. In 
mysql, to lock a row of data at the start of a process to hold 
off concurrent operations, the recommended technique with the 
innodb engine is to issue


SELECT field FROM table FOR UPDATE;

This holds off any other process from accessing that row until 
it is released. This is according to the mysql manual.


My question is, looking through the sqlite documentation, it is 
not clear how sqlite will handle that statement. Since I am 
porting sql between several databases, I am trying to figure out 
if I need to search and destroy any of those statements from 
mysql when converting it to sqlite.



Scott Doctor
sc...@scottdoctor.com
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Re: [sqlite] SELECT FOR UPDATE

[Jay Sprenkle]

Hi,

We are newbie to SQLite and we would like to lock a table through a select +
update.

Something like that:

BEGIN TRANSACTION

   currentValue = select currentValue from sequence_transactions;

   update sequence_transactions set currentValue = currentValue + 1;

   COMMIT;

END TRANSACTION

When the program reachs the select, we would like other threads /
applications wait for that transaction to finish.

Is there any way of achiving that?



Read through the documentation on locking. It should do what you want
and explain
it so you can understand it. I think what you already have written will probably
work fine, but as always, the difficulty is in the details.

http://sqlite.org/lockingv3.html



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[sqlite] SELECT FOR UPDATE

[jfbaro]

Hi,

We are newbie to SQLite and we would like to lock a table through a select +
update.

Something like that:

BEGIN TRANSACTION

   currentValue = select currentValue from sequence_transactions;   

   update sequence_transactions set currentValue = currentValue + 1;

   COMMIT;

END TRANSACTION

When the program reachs the select, we would like other threads /
applications wait for that transaction to finish.

Is there any way of achiving that?

Cheers


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