So does that mean that local hashmap is not controlled with all the heavy locks that are present around the cache? On 22 Jul 2015 07:31, "Alexey Goncharuk" <alexey.goncha...@gmail.com> wrote:
> Metadata cache access is backed by a local hash map, so the real cost is a > String object hashcode which is cached in the String object and a hashmap > lookup by an integer key. > > On the other hand, the marshaller is still pluggable and after the ticket > is completed, it should be fairly easy to implement this approach and > compare performance. > > --Alexey > > 2015-07-21 10:01 GMT-07:00 Sergi Vladykin <sergi.vlady...@gmail.com>: > > > I think O(N) reasoning does not make a real sense here since N is always > > small, lets not fool ourselves. > > To my mind operation cost of cache access (with all busy locks...), > > hashCode/equals and stuff like that has much bigger impact here. > > Do we still have a pluggable marshaller? Can my approach be implemented > > separately? > > > > Sergi > > > > > > > > > > 2015-07-21 9:14 GMT+03:00 Alexey Goncharuk <alexey.goncha...@gmail.com>: > > > > > Currently an index-enabled serialized object form has the following > > layout > > > (simplified): > > > > > > [object fields][field1Offset,field1Length, > > > field2Offset,field2Length,...,fieldNOffset,fieldNLength] > > > > > > where fields order is determined upon the first object serialization > and > > > stored in metadata cache which is available on all nodes. Thus, the > field > > > lookup is performed as follows: > > > > > > fieldName -> fieldIndex (metadata lookup, O(1)), > fieldIndex->fieldOffset > > in > > > footer (O(1)), fieldOffset->fieldValue (O(1)). > > > > > > BTW, I am finalizing the branch with marshaller changes and will send > > this > > > for a preliminary review soon. > > > > > > 2015-07-16 0:55 GMT-07:00 Atri Sharma <atri.j...@gmail.com>: > > > > > > > Keep in mind that JSONB's performance comes from the fact that it > uses > > > > server encoding, is binary represented and can have GIN indexes on > top > > of > > > > it. Not sure if Ignite's marshalling approach keeps those features as > > > well. > > > > > > > > On Thu, Jul 16, 2015 at 1:20 PM, Sergi Vladykin < > > > sergi.vlady...@gmail.com> > > > > wrote: > > > > > > > > > HSTORE and JSONB appeared to have similar format in Postgresql > > (because > > > > > they was developed by the same people). They noticed that they > > switched > > > > off > > > > > of using key length sorting because they sometimes need > > lexicographical > > > > > order but this is irrelevant for us. > > > > > > > > > > Sergi > > > > > > > > > > 2015-07-16 10:43 GMT+03:00 Atri Sharma <atri.j...@gmail.com>: > > > > > > > > > > > Are you referring to JSONB here? > > > > > > > > > > > > On Thu, Jul 16, 2015 at 1:10 PM, Sergi Vladykin < > > > > > sergi.vlady...@gmail.com> > > > > > > wrote: > > > > > > > > > > > > > Guys, specially Alexey G. > > > > > > > > > > > > > > I've attended PostgreSQL conference and there was a talk about > > > > > > unstructured > > > > > > > data format. > > > > > > > They had an interesting idea of serialized layout close enough > to > > > > ours, > > > > > > I'm > > > > > > > not sure how much this is different from our approach and if we > > can > > > > use > > > > > > > some ideas from it but anywaus it looks really promising to me > > and > > > I > > > > > want > > > > > > > to share. > > > > > > > > > > > > > > The structure basically is the following: > > > > > > > > > > > > > > [key headers] [keys] [values] > > > > > > > > > > > > > > Key headers are [key offset, key length] so they are of a fixed > > > > length. > > > > > > > > > > > > > > The cool idea here is that keys and respectively the key > headers > > > > sorted > > > > > > by > > > > > > > (key length, key) so that you can do a lookup first by fast > > picking > > > > key > > > > > > of > > > > > > > the needed length without looking at keys at all and then pick > an > > > > exact > > > > > > > key. Both searches can be done with fast scan if there are > small > > > > number > > > > > > of > > > > > > > keys and binary search for a larger number of keys. > > > > > > > > > > > > > > Alexey G., could you please compare this to our new marshalling > > > > > approach > > > > > > > you are about to merge? > > > > > > > BTW, it would be nice if you will describe it in details here. > > > > > > > > > > > > > > Sergi > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > Regards, > > > > > > > > > > > > Atri > > > > > > *l'apprenant* > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > Regards, > > > > > > > > Atri > > > > *l'apprenant* > > > > > > > > > >
