[Xapian-discuss] "dangerous" patch
olly at survex.com
Thu Jul 1 19:37:42 BST 2004
On Wed, Jun 30, 2004 at 10:44:07PM +0100, Olly Betts wrote:
> Attached is a patch which turns off the B-tree versioning mechanism
> during update. You'll lose atomic updates, so if the indexer or machine
> crashes, you've probably got a useless database. But it reduces the
> number of blocks written which can speed up updating quite a bit if
> it is I/O bound - it's good for reindexing from scratch, for example.
> Here's a couple of graphs showing performance on a fairly low spec
> machine. The first is without, the second with. X axis is database
> size, Y axis is documents added per second:
> These graphs don't show off the gain especially well, but they're what
> I have to hand. Notice how the second graph only drops away from 20
> docs/sec at around 800,000 documents while the first drops below at
> around 350,000.
I realised just overlaying the two graphs would make the difference more
obvious - a couple of minutes with the gimp gives this:
Green is standard, red is "dangerous".
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