On Wed, Oct 26, 2016 at 10:51 AM, Adrien Grand <[email protected]> wrote: > Le mer. 26 oct. 2016 à 16:23, Yonik Seeley <[email protected]> a écrit : >> >> Docvalues benefits is the reason we recommend them by default (and >> non-text fields now do have docvalues by default). >> They do have some drawbacks however: >> - Require reindexing > > > I don't think that one is an issue if the schema examples enable doc values > by default.
People upgrading and using their old schema for example. >> - Take up more index space > > > If doc values are using X GB of disk space, then it means FieldCache would > use *at least* as much *memory*. It sounds pretty weird to me to not be > willing to put on disk something that would reside in memory otherwise. Sure, and things like that are why docvalues are default. But it doesn't follow that it won't be an issue for anyone though. And if one has a workload where writes are much more important than reads (again a minority), and one is IO bound indexing, that larger index space is going to directly translate to worse indexing throughput. >> - Slower than FieldCache > > > It depends what we are talking about. While facets on a static index might > be slightly faster, FieldCache makes reopens much slower. Right. Again, the FieldCache advantages aren't across the board (which is why it's not default). For some though, reopens aren't an issue, and maximum throughput on static indexes is (and more than slightly faster I think, but I'd have to benchmark again...). Just like UnInvertedField (which is arguably part of "uninverted"...), it's *very* expensive to reopen, but some people have decided it's still worth the cost. Additionally, some of the weaknesses in the FieldCache can always be improved in the future. Limitations aren't permanent. -Yonik >> So although the majority will be better served by docvalues, I don't >> think there should be a rush to remove the option of using the >> FieldCache. > > > Doc values have been out for more than 4 years, I don't think I am rushing > anything. FieldCache has existed for a very long time, so it does not look > too terrible, but when you think about it, wouldn't you think it is crazy if > we decided to build an inverted index in memory from stored fields on the > first time that a field is searched on? > > Finally something that annoys me too is that it makes points harder to > integrate since it is expected that a field that is indexed with points > instead of the inverted index should be uninvertable too. --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
