Re: [sqlite] Busy handler not called

2010-11-12 Thread Prakash Reddy Bande 
Hi,

Got it. I did read this, but probably did not understand very well.
Yes, it makes sense why busy handler is not called. May be it is a good idea to 
site some examples in the documentation...

Regards,
 
Prakash Bande
Altair Engg. Inc. 
Troy MI
Ph: 248-614-2400 ext 489
Cell: 248-404-0292
-Original Message-
From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] 
On Behalf Of Jay A. Kreibich
Sent: Friday, November 12, 2010 7:16 PM
To: General Discussion of SQLite Database
Subject: Re: [sqlite] Busy handler not called

On Fri, Nov 12, 2010 at 04:51:11PM -0500, Prakash Reddy Bande scratched on the 
wall:
> Hi,
> 
> I have set a busy handler.
> 
> int ret = sqlite3_open(dbname.c_str(), &m_ppDb);
> sqlite3_busy_handler(m_ppDb, &hwLMsqlite3BusyHandler, 0);
> 
> However it is not getting called.

  As the docs for sqlite3_busy_handler() point out, this is exactly how
  it is expected to work:

  <http://www.sqlite.org/c3ref/busy_handler.html>

  The presence of a busy handler does not guarantee that it will be
  invoked when there is lock contention. If SQLite determines that
  invoking the busy handler could result in a deadlock, it will go
  ahead and return SQLITE_BUSY or SQLITE_IOERR_BLOCKED instead of
  invoking the busy handler. Consider a scenario where one process
  is holding a read lock that it is trying to promote to a reserved
  lock and a second process is holding a reserved lock that it is
  trying to promote to an exclusive lock. The first process cannot
  proceed because it is blocked by the second and the second
  process cannot proceed because it is blocked by the first. If
  both processes invoke the busy handlers, neither will make any
  progress. Therefore, SQLite returns SQLITE_BUSY for the first
  process, hoping that this will induce the first process to
  release its read lock and allow the second process to proceed.



> 1. Using the sqlite3.exe run the following commands
> begin transaction;
> update users set name="hello"
> 
> 2. Note I have not yet commited.

  This will grab the reserved lock, and knows it will want to get an
  exclusive to finish the transaction.

> From my program I call
> 
> int ret = sqlite3_exec(m_ppDb, query.c_str(), &hwLMsqlite3TableCallback, &rs, 
> &zErr);
> 
> I get SQLITE_BUSY and hwLMsqlite3BusyHandler is not getting called.

  You said this is another update, so same thing... Any attempt to
  promote to a reserved lock will sense a possible deadlock and
  skip the busy handler.  At this point, there is no way out of
  this situation other than having the second query rollback.
  Exec is likely to do this automatically, aborting the second
  UPDATE, and returning the original SQLITE_BUSY error.


-j

-- 
Jay A. Kreibich < J A Y  @  K R E I B I.C H >

"Intelligence is like underwear: it is important that you have it,
 but showing it to the wrong people has the tendency to make them
 feel uncomfortable." -- Angela Johnson
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Re: [sqlite] Busy handler not called

2010-11-12 Thread Jay A. Kreibich 
On Fri, Nov 12, 2010 at 04:51:11PM -0500, Prakash Reddy Bande scratched on the 
wall:
> Hi,
> 
> I have set a busy handler.
> 
> int ret = sqlite3_open(dbname.c_str(), &m_ppDb);
> sqlite3_busy_handler(m_ppDb, &hwLMsqlite3BusyHandler, 0);
> 
> However it is not getting called.

  As the docs for sqlite3_busy_handler() point out, this is exactly how
  it is expected to work:

  

  The presence of a busy handler does not guarantee that it will be
  invoked when there is lock contention. If SQLite determines that
  invoking the busy handler could result in a deadlock, it will go
  ahead and return SQLITE_BUSY or SQLITE_IOERR_BLOCKED instead of
  invoking the busy handler. Consider a scenario where one process
  is holding a read lock that it is trying to promote to a reserved
  lock and a second process is holding a reserved lock that it is
  trying to promote to an exclusive lock. The first process cannot
  proceed because it is blocked by the second and the second
  process cannot proceed because it is blocked by the first. If
  both processes invoke the busy handlers, neither will make any
  progress. Therefore, SQLite returns SQLITE_BUSY for the first
  process, hoping that this will induce the first process to
  release its read lock and allow the second process to proceed.



> 1. Using the sqlite3.exe run the following commands
> begin transaction;
> update users set name="hello"
> 
> 2. Note I have not yet commited.

  This will grab the reserved lock, and knows it will want to get an
  exclusive to finish the transaction.

> From my program I call
> 
> int ret = sqlite3_exec(m_ppDb, query.c_str(), &hwLMsqlite3TableCallback, &rs, 
> &zErr);
> 
> I get SQLITE_BUSY and hwLMsqlite3BusyHandler is not getting called.

  You said this is another update, so same thing... Any attempt to
  promote to a reserved lock will sense a possible deadlock and
  skip the busy handler.  At this point, there is no way out of
  this situation other than having the second query rollback.
  Exec is likely to do this automatically, aborting the second
  UPDATE, and returning the original SQLITE_BUSY error.


-j

-- 
Jay A. Kreibich < J A Y  @  K R E I B I.C H >

"Intelligence is like underwear: it is important that you have it,
 but showing it to the wrong people has the tendency to make them
 feel uncomfortable." -- Angela Johnson
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Re: [sqlite] Busy handler not called

2010-11-12 Thread Prakash Reddy Bande 
Hi,

Basically I am doing the same query i.e.
int ret = sqlite3_exec(m_ppDb, "begin transaction", &hwLMsqlite3TableCallback, 
&rs, &zErr);

int ret = sqlite3_exec(m_ppDb, "update users set name=\"something\"", 
&hwLMsqlite3TableCallback, &rs, &zErr);

The second one return SQLITE_BUSY as expected (since begin transaction does no 
locking as per documentation of sqlite)

Regards,
 
Prakash Bande
Altair Engg. Inc. 
Troy MI
Ph: 248-614-2400 ext 489
Cell: 248-404-0292

-Original Message-
From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] 
On Behalf Of Pavel Ivanov
Sent: Friday, November 12, 2010 4:57 PM
To: General Discussion of SQLite Database
Subject: Re: [sqlite] Busy handler not called

> int ret = sqlite3_exec(m_ppDb, query.c_str(), &hwLMsqlite3TableCallback, &rs, 
> &zErr);
>
> I get SQLITE_BUSY and hwLMsqlite3BusyHandler is not getting called.

What query do you use?


Pavel

On Fri, Nov 12, 2010 at 4:51 PM, Prakash Reddy Bande
 wrote:
> Hi,
>
> I have set a busy handler.
>
> int ret = sqlite3_open(dbname.c_str(), &m_ppDb);
> sqlite3_busy_handler(m_ppDb, &hwLMsqlite3BusyHandler, 0);
>
> However it is not getting called. Here is what I am doing:
> 1. Using the sqlite3.exe run the following commands
> begin transaction;
> update users set name="hello"
>
> 2. Note I have not yet commited.
>
> From my program I call
>
> int ret = sqlite3_exec(m_ppDb, query.c_str(), &hwLMsqlite3TableCallback, &rs, 
> &zErr);
>
> I get SQLITE_BUSY and hwLMsqlite3BusyHandler is not getting called.
>
> I am using is 3.7.2
>
> Regards,
>
> Prakash Bande
> Altair Engg. Inc.
> Troy MI
> Ph: 248-614-2400 ext 489
> Cell: 248-404-0292
>
> ___
> sqlite-users mailing list
> sqlite-users@sqlite.org
> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
>
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Re: [sqlite] Busy handler not called

2010-11-12 Thread Pavel Ivanov 
> int ret = sqlite3_exec(m_ppDb, query.c_str(), &hwLMsqlite3TableCallback, &rs, 
> &zErr);
>
> I get SQLITE_BUSY and hwLMsqlite3BusyHandler is not getting called.

What query do you use?


Pavel

On Fri, Nov 12, 2010 at 4:51 PM, Prakash Reddy Bande
 wrote:
> Hi,
>
> I have set a busy handler.
>
> int ret = sqlite3_open(dbname.c_str(), &m_ppDb);
> sqlite3_busy_handler(m_ppDb, &hwLMsqlite3BusyHandler, 0);
>
> However it is not getting called. Here is what I am doing:
> 1. Using the sqlite3.exe run the following commands
> begin transaction;
> update users set name="hello"
>
> 2. Note I have not yet commited.
>
> From my program I call
>
> int ret = sqlite3_exec(m_ppDb, query.c_str(), &hwLMsqlite3TableCallback, &rs, 
> &zErr);
>
> I get SQLITE_BUSY and hwLMsqlite3BusyHandler is not getting called.
>
> I am using is 3.7.2
>
> Regards,
>
> Prakash Bande
> Altair Engg. Inc.
> Troy MI
> Ph: 248-614-2400 ext 489
> Cell: 248-404-0292
>
> ___
> sqlite-users mailing list
> sqlite-users@sqlite.org
> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
>
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[sqlite] Busy handler not called

2010-11-12 Thread Prakash Reddy Bande 
Hi,

I have set a busy handler.

int ret = sqlite3_open(dbname.c_str(), &m_ppDb);
sqlite3_busy_handler(m_ppDb, &hwLMsqlite3BusyHandler, 0);

However it is not getting called. Here is what I am doing:
1. Using the sqlite3.exe run the following commands
begin transaction;
update users set name="hello"

2. Note I have not yet commited.

>From my program I call

int ret = sqlite3_exec(m_ppDb, query.c_str(), &hwLMsqlite3TableCallback, &rs, 
&zErr);

I get SQLITE_BUSY and hwLMsqlite3BusyHandler is not getting called.

I am using is 3.7.2

Regards,

Prakash Bande
Altair Engg. Inc.
Troy MI
Ph: 248-614-2400 ext 489
Cell: 248-404-0292

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