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To:	cygwin AT cygwin DOT com
From:	Achim Gratz <Stromeko AT nexgo DOT de>
Subject:	Re: [ANNOUNCEMENT] [TEST] sqlite3-3.7.17-3
Date:	Thu, 13 Jun 2013 19:07:10 +0200
Lines:	44
Message-ID:	<87vc5i548x.fsf@Rainer.invalid>
References:	<announce DOT 51B73B35 DOT 7010206 AT etr-usa DOT com>
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User-Agent:	Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)

Warren Young writes:
> This version of Cygwin SQLite also makes one other big, potentially
> breaking change: temporary files are created in-memory exclusively, by
> default.

I've been reading the documentation for that option again and it appears
that eventually the temporary table _will_ be committed to disk anyway
when it exceeds some size threshold (or SQLite runs out of page
buffers), so it looks that whatever problems with creating or using such
an actual file should manifest itself before the table gets that large.
This would also explain why there is no strong warning about this
potentially breaking with large temporary tables, I'd think.

> There is some concern that this could cause problems with huge DB
> files on 32-bit Cygwin.  If this version of SQLite fails with some
> out-of-memory error with your DB, there is a pragma you can set to
> make it behave the old way:
>
> 	https://www.sqlite.org/pragma.html#pragma_temp_store
>
> If setting this pragma to 1 fixes such an error, I want to hear it!
> (I'd also be curious to know how big the DB file is, and how much RAM
> there is in your machine.)

A new version of DBD::SQLite was released just recently, so I took the
occasion and built it against the test version of sqlite3 today.  I've
added "pragma TEMP_STORE=1" to the test that originally triggered the
"treat Cygwin as UNIX" saga and this still works, not setting
CYGWIN_SQLITE_LOCKING to anything at all.  That test doesn't have
concurrency so locking is not really involved, however I can't see why
temp table files and locking would interfere at all.  I think it would
be exceedingly rare that any other process would know the name of the
file backing the table or the directory that it lives in.  I've lost
track of what values use which locking strategy in the latest build, so
let me know if I should try a something different as well.


Regards,
Achim.
-- 
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