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Fix for ticket #111: Update the documentation to explain that you may not

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start a transaction in one thread and complete it in another thread under
Linux Threads where each thread has its own process ID. (CVS 695)

FossilOrigin-Name: 0b0c0492cc1e55c1c4feba6e92765ea09896096c
This commit is contained in:
drh
2002-07-30 17:42:10 +00:00
parent 62160e798c
commit c51d204464
4 changed files with 50 additions and 10 deletions
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36
www/c_interface.tcl
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@ -1,7 +1,7 @@
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: c_interface.tcl,v 1.31 2002/07/13 17:18:37 drh Exp $}
set rcsid {$Id: c_interface.tcl,v 1.32 2002/07/30 17:42:10 drh Exp $}
puts {<html>
<head>
@ -301,6 +301,9 @@ is used incorrectly. Examples of incorrect usage include calling
<b>sqlite_exec()</b> after the database has been closed using
<b>sqlite_close()</b> or calling <b>sqlite_exec()</b> with the same
database pointer simultaneously from two separate threads.
This error code will also be returned under Unix if <b>sqlite_exec()</b>
is called while a transaction is pending that was started in another
process or thread that has a different process ID.
</p></dd>
</dl>
</blockquote>
@ -792,6 +795,37 @@ new SQL functions, review the SQLite source code in the file
<b>func.c</b>.
</p>
<h2>Multi-Threading And SQLite</h2>
<p>
If SQLite is compiled with the THREADSAFE preprocessor macro set to 1,
then it is safe to use SQLite from two or more threads of the same process
at the same time. But each thread should have its own <b>sqlite*</b>
pointer returned from <b>sqlite_open()</b>. It is never safe for two
or more threads to access the same <b>sqlite*</b> pointer at the same time.
</p>
<p>
In precompiled SQLite libraries available on the website, the Unix
versions are compiled with THREADSAFE turned off but the windows
versions are compiled with THREADSAFE turned on. If you need something
different that this you will have to recompile.
</p>
<p>
Under Unix, an <b>sqlite*</b> pointer should not be carried across a
<b>fork()</b> system call into the child process. The child process
should open its own copy of the database after the <b>fork()</b>.
</p>
<p>
When using LinuxThreads (where each thread has its own process ID)
it is illegal to start a transaction in one thread and then attempt
to read or write the database from a different thread. This
restriction does not apply to Posix threads where all threads share
the same process ID.
</p>
<h2>Usage Examples</h2>
<p>For examples of how the SQLite C/C++ interface can be used,