update-apt-xiapian-index uses too much memory with a large amount of package sources

I was wondering why my system suddenly started to swap a lot shortly after resume from suspend and found that update-apt-xiapian-index was the culprit after force-oomkill-ing some things to get the system responsive again.

After watching it a bit, top showed this:
PID USER PR NI VIRT RES SHR SWAP S %CPU %MEM TIME+ COMMAND
  20183 root 39 19 1500m 1.3g 3744 99m R 99.4 35.8 3:31.91 /usr/bin/python /usr/sbin/update-apt-xapian-index --quiet

My sources.list is comparatively huge, but an automatically triggered background process shouldn't require almost 1.5G of memory (that's a lot on a system with 4G available)

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: apt-xapian-index 0.45ubuntu3
ProcVersionSignature: Ubuntu 3.11.0-15.25-generic 3.11.10
Uname: Linux 3.11.0-15-generic x86_64
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: amd64
Date: Thu Feb 13 09:54:16 2014
EcryptfsInUse: Yes
MarkForUpload: True
PackageArchitecture: all
SourcePackage: apt-xapian-index
UpgradeStatus: Upgraded to saucy on 2013-03-06 (343 days ago)