Change 546763 had a related patch set uploaded (by Hoo man; owner: Hoo man):
[mediawiki/extensions/Wikibase@master] Don't store EntityUsage objects in ParserOutput, but minimal identifiers

https://gerrit.wikimedia.org/r/546763

Change 546763 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@master] Don't store EntityUsage objects in ParserOutput, but minimal identifiers

https://gerrit.wikimedia.org/r/546763

I collected some data about the parser cache sizes of the ruwiki pages with the most hits this month (as per stats.wikimedia.org).

With that I found that currently, for all of these articles:

1. The average PC size is 103986.95
2. The median PC size is 73419.5
3. The minimum PC size is 13313
4. The maximum PC size is 399637

For that I took the ParserCache objects, serialized and gzdeflated them, like SqlBagOStuff does. I also looked into using gzcompress with level 9, like MemcachedClient does, but that doesn't seem to have much of an impact.

With this data as baseline we can roughly estimate the impact this will have on highly visited pages.

The scripts I used can be found in P9535.

I purged all pages from above (which haven't been re-parsed since) and gathered new numbers:

1. The average PC size is 101219.66 (down ~2.7%)
2. The median PC size is 68137 (down ~7.2%)
3. The minimum PC size is 12911 (down ~3.1%)
4. The maximum PC size is 393856 (down ~1.4%)