Agreed. Perhaps I will abandon the static init. I really only put it as
an option due to your synchronized cost concerns (a preload allows non
synched read only access to the indexaccessor cache). Due keep in mind
that you don't have to use it though...if you dont preload, accessors
are created on demand but require you to go through a synch block.
I have some ideas and I will be making an attempt to smooth this all out
tonight. Thanks for your input.
- Mark
Jay Yu wrote:
I agree with you on the compromise aspect of the design.
In particular, I think it's hard to preload all the index accessors in
the static init while allowing users specify the analyzer for each dir
without requiring complicated config file ans using reflection.
So a good compromise might be abandon preload the accessors. After
all, the accessors are cached and not created often.
Thanks!
Jay
Mark Miller wrote:
I think its just a compromise in the design, though it could be
improved. You only ever want a single Writer at a time on the index.
Those two flags are really just hints for when a Writer is first
opened...should it auto-commit and should it overwrite/create...if a
thread tries to writer concurrently with another thread, they will
briefly share a Writer, but generally a new Writer is created fairly
often.
The general strategy should be to pick constant values and always
pass them. There is an opening for the issue that you have a Writer
and are adding a doc, and then before releasing that Writer, another
Writer from another thread tries to clear the index with a
create=true, and it won't work. That's not a big concern though.
So the problem really is that these params control what happens when
a new writer is created, but your not guaranteed to be creating a
Writer, it may be cached. You really should pass the same autocommit
flag , though its not necessary. I am open to suggestions for a more
coherent design, but functionally, it does work. I am also thinking
about how to handle the Analyzer, and I think the solution (the need
to init some indexaccessor params) might involve all these issues.
- Mark
Jay Yu wrote:
Mark,
Looking at your implementation of the DefaultIndexAccessor regarding
the writer, I think there could be a problem: you have only one
cached writer but the getWriter(boolean, boolean) allows 2 booleans,
so ideally, you need 4 cached writer. Otherwise if one starts with a
writer that over writes the existing index, then later he cannot
append docs to the index.
Do I miss sth here or you have not finished the implementation of
getWriter yet?
Thanks!
Jay
Mark Miller wrote:
Ah, thanks for catching that. One of the pieces I did not
finish...the keyword analyzer was placeholder code.
I will take your comments into account and update the code.
I have some other pieces to polish as well. Previously, I extended
and built upon the original code, but I can't give it away, so this
is my attempt at something lessor, but cleaner.
Jay Yu wrote:
Thanks for the tip.
One small improvement on the IndexAccessorFactory might be to
allow user to specify the Analyzer instead of using a default
KeywordAnalyzer, which of course will make your static init of the
cached accessors difficult unless you add more interfaces to the
accessor to allow reset analyzer/Dir as in my own version.
Jay
Mark Miller wrote:
One final note....if you are using the IndexAccessor and you are
only accessing the index from one JVM, you can use the
NoLockFactory and save some sync cost there.
Jay Yu wrote:
Mark,
Great effort getting the original lucene index accessor package
in this shape. I am sure this will benefit a lot of people using
Lucene in a multithread env.
I have a quick question to ask you:
Do you have to use the core Lucene 2.3-dev in order to use the
accessor?
I will take a look at your codes to see if I could help. I used
a slightly modified version of the original package in my
project but it breaks some of my tests. I hope your version
works better.
Thanks a lot!
Jay
Mark Miller wrote:
I have sat down and rewrote IndexAccessor from scratch. I
copied in the same reference counting logic, pruned some
things, and tried to make the whole package a bit simpler to
use. I have a few things to do, but its pretty solid already.
The only major thing I'd still like to do is add an option to
warm searchers before putting them in the Searcher cache. Id
like to writer some more tests as well. Any help greatly
appreciated if your interested in using the thing.
http://myhardshadow.com/indexaccessor/trunk/src/test/com/mhs/indexaccessor/SimpleSearchServer.java
Here is a an example of a class that can be instantiated in one
of multiple threads and read /modify a single index without
worrying about what any
of the other threads are doing to the index at any given time.
This is a very simple example of how to use the IndexAccessor
and not necessarily an
example of best practices. The main idea is that you get your
Writer, Searcher, or Reader, and then be sure to release it as
soon as your done with it
in a finally block. For loading, you will want to load many
docs with a Writer (batch them) before releasing it, but
remember that Readers will not get a new view
of the index until you release all of the Writers. So beware
hogging a Writer unless you thats what your intending.
JavaDoc:
http://myhardshadow.com/indexaccessorapi/
Code:
http://myhardshadow.com/indexaccessor/trunk/
Jar:
http://myhardshadow.com/indexaccessorreleases/indexaccessor.jar
Your synchronized block concerns:
The synchronized blocks that control accesss to the
IndexAccessor do not have a huge impact on performance. Keep in
mind that all of the work is not done in a synchonrized block,
just the retrieval of the Searcher, Writer, Reader. Even if the
synchronization makes the method twice as expensive, it is
still overpowered by the cost of parsing queries and searching
the index. This applies with or without contention. I wrote a
simple test and included the output below. You might use the
IBM Lock Analyzer for Java to further analyze these costs.
Trust me, this thing is speedy. Its many times better than
using IndexModifier.
Without Contention
Just retrieve and release Searcher 100000 times
----
avg time:6.3E-4 ms
total time:63 ms
Parse query and search on 1 doc 100000 times
----
avg time:0.03107 ms
total time:3107 ms
With Contention (40 other threads running 80000 searches)
Just retrieve and release Searcher 100000 times
----
avg time:0.04643 ms
total time:4643 ms
Parse query and search on 1 doc 100000 times
----
avg time:0.64337 ms
total time:64337 ms
- Mark
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