Re: [Wikitech-l] Can we drop revision hashes (rev_sha1)?

Compute the hashes on the fly for the offline analysis doesn’t work for Wikistats 1.0, as it only parses the stub dumps, without article content, just metadata. Parsing the full archive dumps is a quite expensive, time-wise. This may change with Wikistats 2.0 with has a totally different process flow. That I can't tell. Erik Zachte -----Original Message----- From: Wikitech-l [mailto:wikitech-l-bounces@lists.wikimedia.org] On Behalf Of Daniel Kinzler Sent: Friday, September 15, 2017 12:52 To: Wikimedia developers &lt;wikitech-l(a)lists.wikimedia.org&gt; Subject: [Wikitech-l] Can we drop revision hashes (rev_sha1)? Hi all! I'm working on the database schema for Multi-Content-Revisions (MCR) < https://www.mediawiki.org/wiki/Multi-Content_Revisions/Database_Schema> and I'd like to get rid of the rev_sha1 field: Maintaining revision hashes (the rev_sha1 field) is expensive, and becomes more expensive with MCR. With multiple content objects per revision, we need to track the hash for each slot, and then re-calculate the sha1 for each revision. That's expensive especially in terms of bytes-per-database-row, which impacts query performance. So, what do we need the rev_sha1 field for? As far as I know, nothing in core uses it, and I'm not aware of any extension using it either. It seems to be used primarily in offline analysis for detecting (manual) reverts by looking for revisions with the same hash. Is that reason enough for dragging all the hashes around the database with every revision update? Or can we just compute the hashes on the fly for the offline analysis? Computing hashes is slow since the content needs to be loaded first, but it would only have to be done for pairs of revisions of the same page with the same size, which should be a pretty good optimization. Also, I believe Roan is currently looking for a better mechanism for tracking all kinds of reverts directly. So, can we drop rev_sha1? -- Daniel Kinzler Principal Platform Engineer Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V. _______________________________________________ Wikitech-l mailing list Wikitech-l(a)lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikitech-l _______________________________________________ Wikitech-l mailing list Wikitech-l(a)lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikitech-l