Re: parallel restore vs. windows

Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:

> I did this, but it turned out that the problem was a logic error that I
> found once I had managed to get a working debugger. However, the Windows
> thread code should now be more robust, so thanks to Andrew and Magnus
> for the suggestions.

Hello, I tested parallel restore on Windows.
I have some random comments about it:

* Two compiler warnings.
pg_backup_custom.c: In function `_PrintTocData':
pg_backup_custom.c:437: warning: unused variable `ctx'
pg_backup_custom.c: In function `_ReopenArchive':
pg_backup_custom.c:849: warning: unused variable `ctx'

* No description about new options in pg_restore --help.
There are no help messages about multi-thread (-m) and
truncate-before-load options.

* multi-thread option is ignored if --data-only is on.
Is it an intended behavior? Even if so, we'd better to have
warning messages here.

* Threads, forked processes and connections are disposed per entry.
I think it's a designed behavior, but there might be room for
improvement. The present implementation is slower when there
are many small objects. If we can specialize in thread-based
implementation, thread pooling and connections pooling are
typically used in the context. -- it might be a ToDo item in 8.5.

----
I have no idea about performance because I don't have multi-core
machine for windows. Parallel restore seems to be slower than
serial restore on single-cpu machine.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center