Yes, I think bringing in a mutable file in lucene-index brings it's own set of problems to handle. Filters, Caches, Scoring, Snapshots/Commits etc... will all be affected.
There is on JIRA on writing generation of updatable files, just like doc-deletes instead of over-writing a single file.[ https://issues.apache.org/jira/browse/LUCENE-4258]. But that is still in-progress and from what I understand, it could slow searches considerably. BTW, is it possible to extend BlurPartitioner and load it during start-up? Also, it would be awesome if Blur supports a per-row auto-complete feature. -- Ravi On Sat, Oct 5, 2013 at 2:01 AM, Aaron McCurry <[email protected]> wrote: > I have thought of one possible problem with this approach. To date the > mindset I have used in all of the Blur internals is that segments are > immutable. This is a fundamental principle that Blur uses and I don't > really have any ideas on where to behind checking for when this is a > problem. I know filters are going to be an issue, not sure where else. > > Not saying that it can't be done, it's just not going to be as clean as I > originally thought. > > Aaron > > > On Fri, Oct 4, 2013 at 4:26 PM, Aaron McCurry <[email protected]> wrote: > > > > > > > On Fri, Oct 4, 2013 at 7:15 AM, Ravikumar Govindarajan < > > [email protected]> wrote: > > > >> On a related note, do you think such an approach will fit in Blur > >> > >> 1. Store the BDB file in shard-server itself. > >> > > > > Probably not, this would pin the BDB (or whatever the solution would be) > > to a specific server. We will have to sync to HDFS. > > > > > >> > >> 2. Apply all incoming partial doc-updates to local BDB file as well as > an > >> update-transaction log > >> > > > > Blur already has a write ahead log as apart of internals. It's written > > and synced to HDFS. > > > > > >> > >> 3. Periodically sync dirty BDB files to HDFS and roll-over the update- > >> transaction log. > > > > > >> Whenever a shard-server goes down, the take-over server can initially > sync > >> the BDB file from HDFS to local, replay the update-transaction log and > >> then > >> start serving data > >> > > > > Blur already does this internally, it records the mutates and replays > them > > if a failure happens before a commit. > > > > Aaron > > > > > >> > >> -- > >> Ravi > >> > >> > >> On Thu, Oct 3, 2013 at 11:14 PM, Ravikumar Govindarajan < > >> [email protected]> wrote: > >> > >> > The mutate APIs are a good fit for individual cols update. BlurCodec > >> will > >> > be cool and solve a lot of problems. > >> > > >> > There are 3 caveats for such a codec > >> > > >> > 1. Scores for affected queries will be wrong, until segment-merge > >> > > >> > 2. Responsibility of ordering updates must be on the client. > >> > > >> > 3. Repeated updates for the same document can either take a > generational > >> > approach [Lucene-4258] or use a single version of storage [Redis/TC > >> etc..], > >> > pushing the onus to client, depending on how the Codec shapes up. > >> > > >> > The former will be semantically correct but really sluggish while the > >> > latter will be faster during search > >> > > >> > > >> > > >> > On Thu, Oct 3, 2013 at 8:53 PM, Aaron McCurry <[email protected]> > >> wrote: > >> > > >> >> On Thu, Oct 3, 2013 at 11:08 AM, Ravikumar Govindarajan < > >> >> [email protected]> wrote: > >> >> > >> >> > Yeah, you are correct. A BDB file might probably never be ported to > >> >> HDFS. > >> >> > > >> >> > Our daily update frequency comes to about 20% of insertion rate. > >> >> > > >> >> > Lets say "UPDATE <TABLE> SET COL2=1 WHERE COL1=X". > >> >> > > >> >> > This update could potentially span across tens of thousands of SQL > >> rows > >> >> in > >> >> > our case, where COL2 is just a boolean flip. > >> >> > > >> >> > The problem is not with lucene's ability to handle load. Instead it > >> is > >> >> with > >> >> > the consistent load it puts on our content servers to read and > >> >> re-tokenize > >> >> > such huge rows just for a boolean flip. Another big winner is that > >> all > >> >> our > >> >> > updatable fields are not involved in scoring at all. Just matching > >> will > >> >> do. > >> >> > > >> >> > The changes also sit in BDB only till the next segment merge, after > >> >> which > >> >> > it is cleaned out. There is very little perf hit here for us, as > >> users > >> >> > don't immediately search after a change. > >> >> > > >> >> > I am afraid there is no documentation/code/numbers on this > currently > >> in > >> >> > public, as it is still proprietary but is remarkably similar to the > >> >> popular > >> >> > to RedisCodec. > >> >> > > >> >> > "If you really need partial document updates, there would need to > be > >> >> > changes > >> >> > throughout the entire stack" > >> >> > > >> >> > You mean, the entire stack of Blur? In case this is possible, can > you > >> >> give > >> >> > me 10000-ft overview of what you have in mind? > >> >> > > >> >> > >> >> Interesting, now that I think about it. The situation that you > >> describe > >> >> is > >> >> very interesting, I'm wondering if we came up with something like > this > >> in > >> >> Blur that it would fix our large Row issue. Or at the very least > help > >> the > >> >> problem. > >> >> > >> >> https://issues.apache.org/jira/browse/BLUR-220 > >> >> > >> >> Plus the more I think about it, the mutate methods are probably the > >> right > >> >> implementation for modifying single columns. So the API of Blur > >> probably > >> >> wouldn't need to be changed. Maybe just the way it goes about > dealing > >> >> with > >> >> changes. I thinking maybe we need our own BlurCodec to handle large > >> Rows > >> >> as well as Record (Document) updates. > >> >> > >> >> As an aside I constantly am having to refer to Records as Documents, > >> this > >> >> is why I think we need a rename. > >> >> > >> >> Aaron > >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > > >> >> > -- > >> >> > Ravi > >> >> > > >> >> > > >> >> > On Thu, Oct 3, 2013 at 5:36 PM, Aaron McCurry <[email protected]> > >> >> wrote: > >> >> > > >> >> > > The biggest issue with this is that the shards (the indexes) > >> inside of > >> >> > Blur > >> >> > > actually move from one server to another. So to support this > >> behavior > >> >> > all > >> >> > > the indexes are stored in HDFS. Do due the differences between > >> HDFS > >> >> and > >> >> > > the a normal POSIX file system, I highly doubt that the BDB file > >> form > >> >> in > >> >> > > TokyoCabinet can ever be supported. > >> >> > > > >> >> > > If you really need partial document updates, there would need to > be > >> >> > changes > >> >> > > throughout the entire stack. I am curious why you need this > >> feature? > >> >> Do > >> >> > > you have that many updates to the index? What is the update > >> >> frequency? > >> >> > > I'm just curious of what kind of performance you get out of a > >> setup > >> >> like > >> >> > > that? Since I haven't ever run such a setup I have no idea how > to > >> >> > compare > >> >> > > that kind of system to a base Lucene setup. > >> >> > > > >> >> > > Could you point be to some code or documentation? I would to go > >> and > >> >> > take a > >> >> > > look. > >> >> > > > >> >> > > Thanks, > >> >> > > Aaron > >> >> > > > >> >> > > > >> >> > > > >> >> > > On Thu, Oct 3, 2013 at 7:00 AM, Ravikumar Govindarajan < > >> >> > > [email protected]> wrote: > >> >> > > > >> >> > > > One more help. > >> >> > > > > >> >> > > > We also maintain a file by name "BDB", just like the "Sample" > >> file > >> >> for > >> >> > > > tracing used by Blur. > >> >> > > > > >> >> > > > This "BDB" file pertains to TokyoCabinet and is used purely for > >> >> > > supporting > >> >> > > > partial updates to a document. > >> >> > > > All operations on this file rely on local file-paths only, > >> through > >> >> the > >> >> > > use > >> >> > > > of native code. > >> >> > > > Currently, all update requests are local to the index files and > >> it > >> >> > > becomes > >> >> > > > trivial to support. > >> >> > > > > >> >> > > > Any pointers on how to take this forward in Blur set-up of > >> >> > shard-servers > >> >> > > & > >> >> > > > controllers? > >> >> > > > > >> >> > > > -- > >> >> > > > Ravi > >> >> > > > > >> >> > > > > >> >> > > > On Tue, Oct 1, 2013 at 10:15 PM, Aaron McCurry < > >> [email protected]> > >> >> > > wrote: > >> >> > > > > >> >> > > > > You can control the fields to warmup via: > >> >> > > > > > >> >> > > > > > >> >> > > > > > >> >> > > > > >> >> > > > >> >> > > >> >> > >> > http://incubator.apache.org/blur/docs/0.2.0/Blur.html#Struct_TableDescriptor > >> >> > > > > > >> >> > > > > The preCacheCols field. The comment is wrong however, so I > >> will > >> >> > > create a > >> >> > > > > task to correct. The use of the field is: "family.column" > just > >> >> like > >> >> > > you > >> >> > > > > would search. > >> >> > > > > > >> >> > > > > Aaron > >> >> > > > > > >> >> > > > > > >> >> > > > > On Tue, Oct 1, 2013 at 12:41 PM, Ravikumar Govindarajan < > >> >> > > > > [email protected]> wrote: > >> >> > > > > > >> >> > > > > > Thanks Aaron > >> >> > > > > > > >> >> > > > > > General sampling and warming is fine and the code is really > >> >> concise > >> >> > > and > >> >> > > > > > clear. > >> >> > > > > > > >> >> > > > > > The act of reading > >> >> > > > > > brings the data into the block cache and the result is that > >> the > >> >> > index > >> >> > > > is > >> >> > > > > > "hot". > >> >> > > > > > > >> >> > > > > > Will all the terms of a field be read and brought into the > >> >> cache? > >> >> > If > >> >> > > > so, > >> >> > > > > > then it has an obvious implication to avoid fields like, > say > >> >> > > > > > attachment-data from warming up, provided queries don't > often > >> >> > include > >> >> > > > > such > >> >> > > > > > fields > >> >> > > > > > > >> >> > > > > > > >> >> > > > > > On Tue, Oct 1, 2013 at 7:58 PM, Aaron McCurry < > >> >> [email protected]> > >> >> > > > > wrote: > >> >> > > > > > > >> >> > > > > > > Take a look at this package. > >> >> > > > > > > > >> >> > > > > > > > >> >> > > > > > > > >> >> > > > > > > >> >> > > > > > >> >> > > > > >> >> > > > >> >> > > >> >> > >> > https://git-wip-us.apache.org/repos/asf?p=incubator-blur.git;a=tree;f=blur-store/src/main/java/org/apache/blur/lucene/warmup;h=f4239b1947965dc7fe8218eaa16e3f39ecffdda0;hb=apache-blur-0.2 > >> >> > > > > > > > >> >> > > > > > > Basically when the warmup process starts (which is > >> >> asynchronous > >> >> > to > >> >> > > > the > >> >> > > > > > rest > >> >> > > > > > > of the application) it flips a thread local switch to > allow > >> >> for > >> >> > > > tracing > >> >> > > > > > of > >> >> > > > > > > the file accesses. The sampler will sample each of the > >> >> fields in > >> >> > > > each > >> >> > > > > > > segment and create a sample file that attempts to detect > >> the > >> >> > > > boundaries > >> >> > > > > > of > >> >> > > > > > > each field within each file within each segment. Then it > >> >> stores > >> >> > > the > >> >> > > > > > sample > >> >> > > > > > > info into the directory beside each segment (so that way > it > >> >> > doesn't > >> >> > > > > have > >> >> > > > > > to > >> >> > > > > > > re-sample the segment). After the sampling is complete > or > >> >> > loaded, > >> >> > > > the > >> >> > > > > > > warmup just reads the binary data from each file. The > act > >> of > >> >> > > reading > >> >> > > > > > > brings the data into the block cache and the result is > that > >> >> the > >> >> > > index > >> >> > > > > is > >> >> > > > > > > "hot". > >> >> > > > > > > > >> >> > > > > > > Hope this helps. > >> >> > > > > > > > >> >> > > > > > > Aaron > >> >> > > > > > > > >> >> > > > > > > > >> >> > > > > > > > >> >> > > > > > > > >> >> > > > > > > On Tue, Oct 1, 2013 at 10:09 AM, Ravikumar Govindarajan < > >> >> > > > > > > [email protected]> wrote: > >> >> > > > > > > > >> >> > > > > > > > As I understand, > >> >> > > > > > > > > >> >> > > > > > > > Lucene will store the files in following way > per-segment > >> >> > > > > > > > > >> >> > > > > > > > TIM file > >> >> > > > > > > > Field1 ---> Some byte[] > >> >> > > > > > > > Field2 ---> Some byte[] > >> >> > > > > > > > > >> >> > > > > > > > TIP file > >> >> > > > > > > > Field1 ---> Some byte[] > >> >> > > > > > > > Field2 ---> Some byte[] > >> >> > > > > > > > > >> >> > > > > > > > > >> >> > > > > > > > Blur will "sample" this lucene-file in the following > way > >> >> > > > > > > > > >> >> > > > > > > > Field1 --> <TIM, start-offset>, <TIP, start-offset>, > ... > >> >> > > > > > > > > >> >> > > > > > > > Field 2 --> <TIM, start-offset>, <TIP, start-offset>, > ... > >> >> > > > > > > > > >> >> > > > > > > > Is my understanding correct? > >> >> > > > > > > > > >> >> > > > > > > > How does Blur warm-up the fields, when it does not know > >> the > >> >> > > > > > "end-offset" > >> >> > > > > > > or > >> >> > > > > > > > the "length" for each field to warm. > >> >> > > > > > > > > >> >> > > > > > > > Will it by default read all Terms of a field? > >> >> > > > > > > > > >> >> > > > > > > > -- > >> >> > > > > > > > Ravi > >> >> > > > > > > > > >> >> > > > > > > > >> >> > > > > > > >> >> > > > > > >> >> > > > > >> >> > > > >> >> > > >> >> > >> > > >> > > >> > > > > >
