VFS FCNTL question

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VFS FCNTL question

J Decker
https://sqlite.org/c3ref/c_fcntl_busyhandler.html

#define SQLITE_FCNTL_PDB 30

SQLITE_FCNTL_PDB has no documentation as to what it's for.
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Re: VFS FCNTL question

Cezary H. Noweta
Hello,

On 2017-12-03 17:41, J Decker wrote:
> https://sqlite.org/c3ref/c_fcntl_busyhandler.html
>
> #define SQLITE_FCNTL_PDB 30
>
> SQLITE_FCNTL_PDB has no documentation as to what it's for.
The only place, where this FCNTL is used, is btree.c:sqlite3BtreeOpen().
The FCNTL informs a VFS driver on sqlite3 * connection using BTree file.

It is useful when your VFS driver uses time-consuming I/O operations
(for example, over a network) and asynchronous sqlite3_interrupt() has
been invoked. Your driver can periodically check a status of sqlite3's
isInterrupted flag and immediately stop time-consuming I/O without
wasting a time for retrieving/writing a data which would be finally
discarded due to an interrupt.

-- best regards

Cezary H. Noweta
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