[Xapian-discuss] 1.2.2/3 performance issue

[Markus Wörle]

Hi,

I noticed a decrease of query-performance when upgrading from xapian 1.2.0 to 1.2.2 (1.2.3 also makes no difference).

I am constantly benchmarking our setup by recording the average execution time of a query, the amount of slow-queries (queries that took > 0.5 seconds in my case), and the execution time of the slowest query within 5 minutes. With 1.2.2, the average execution time increased about 20-30%, slow-queries nearly doubled, and so did the slowest-query-maximum. I am measuring the plain in-xapian execution-time only, that is without any influence by a query-parser or other overhead.

I can reproduce it with flint as well as the chert backend (where chert ist generally a bit faster). Both speed up when downgrading to 1.2.0 and speed down again when upgrading to 1.2.2 or 1.2.3.

I did not do further testing so far. Next step could be either to log all queries to check which types of queries are affected most, or trying to reproduce it in a testing environment.

Do have any idea yet what change from 1.2.0 to 1.2.2 could have been caused the slowdown?

Regards,
mrks