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From Preetham Kajekar <>
Subject Re: Combining results of multiple indexes
Date Wed, 17 Dec 2008 15:46:53 GMT
Hi Erick,
 Thanks for the response. Replies inline.

Erick Erickson wrote:
> The very first question is always "are you opening a new searcher
> each time you query"? But you've looked at the Wiki so I assume not.
> This question is closely tied to what kind of latency you can tolerate.
> A few more details, please. What's slow? Queries? Indexing?
Indexing. Again, it is not slow. It is just faster with two separate 
indexers in two threads.
> How slow? 100ms? 100s? What are your target times and
> what are you seeing?
With a single indexer in a single thread, I can index about 20,000 event 
objects per second. With 2 thread and 2 indexers, it is close to 50,000. :-)
> How big is your index? 100M? 100G? What kind of VM
> parameters are you specifying?
The index will have about 20mil entries. The size of the index lands up 
being about 500M.
I start the VM with 1G of heap. No other options for GC etc is used.
> As an aside, do note that there's no requirement in Lucene that
> each document have the same fields, so it's unclear why you
> need two indexes, but perhaps some of the answers to the above
> will help us understand.
Like I mentioned, Lucene does the job much faster with two indexes.
> Also, be very very careful what you measure when you measure
> queries. You absolutely *have* to put some instrumentation in
> the code since "slow queries" can result from things other than
> searching. For instance, iterating over a Hits object for 100s of
> documents....
The Query speeds are much faster than what I need :-) So no complains here.
> Show the code, man <G>!
Code below. EvIndexer is the base class. There are two subclasses which 
implement addEvFieldsToIndexDoc() (template pattern) to add different 
fields to the index. that code is also pasted below

--Code ---


    public EvIndexer(String indexName) throws Exception { = indexName;
        a = new KeywordAnalyzer();
        INDEX_PATH = System.getProperty(StoreManager.PROP_DB_DB_LOC, 
        FSDirectory directory = FSDirectory.getDirectory(INDEX_PATH + 
File.separatorChar + indexName, NoLockFactory.getNoLockFactory());
        indexWriter = new IndexWriter(directory, a, 
    /** Method implemented by extending classes to add data into the 
index document for the
     *  given event
     * @param d
    protected abstract void addEvFieldsToIndexDoc(Document d, Ev event);
    public void addToIndex(Ev ev) throws Exception {
        Document d = new Document();      
        addEvFieldsToIndexDoc(d, ev);
        if ((noOfEventsIndexed % COMMIT_INTERVAL) == 0) {
            System.out.println(name + " indexed " + 
NumberFormat.getInstance().format(noOfEventsIndexed) + " Commiting them");

    protected void addEvFieldsToIndexDoc(Document d, Ev ev) {
        Field id = new Field(EV_ID, Long.toString(ev.getId()), 
Field.Store.YES, Field.Index.NO);
        Field src = new Field(EV_SRC, Long.toString(ev.getSrcId()), 
Field.Store.NO, Field.Index.NOT_ANALYZED);
        Field type = new Field(EV_TYPE, 
Integer.toString(ev.getEventTypeId()), Field.Store.NO, 
        Field pri = new Field(EV_PRI, Short.toString(ev.getPriority()) , 
Field.Store.NO, Field.Index.NOT_ANALYZED);
        Field time = new Field(EV_TIME, getHexString(ev.getRecvTime()) , 
Field.Store.NO, Field.Index.NOT_ANALYZED);
        //noOfFieldsIndexed +=  4;

Thanks for the support.

> Best
> Erick
> On Wed, Dec 17, 2008 at 9:40 AM, Preetham Kajekar <>wrote:
>> Hi Grant,
>> Thanks four response. Replies inline.
>> Grant Ingersoll wrote:
>>> On Dec 17, 2008, at 12:57 AM, Preetham Kajekar wrote:
>>>  Hi,
>>>> I am new to Lucene. I am not using it as a pure text indexer.
>>>> I am trying to index a Java object which has about 10 fields (like id,
>>>> time, srcIp, dstIp) - most of them being numerical values.
>>>> In order to speed up indexing, I figured that having two separate
>>>> indexers, each of them indexing different set of fields works great. So I
>>>> have the first 5 fields in index1 and the remaining in index2.
>>> Can you explain this a bit more?  Are those two fields really large org
>>> something?  How are you obtaining them?  How are you correlating the
>>> documents between the two indexes?  Did you actually try a single index and
>>> it was too slow?
>> I have a java object which has about 10 fields. However, the fields are not
>> fixed. The java object is essentially a representation of Syslogs from
>> network devices. So different syslogs have different fields. Each field has
>> a unique id and a value (mostly numeric types, so i convert it to string).
>> There are some fixed fields. So the object is a list of fields which is
>> produced by a parser.
>> I am trying to index using two indexers in two separate threads- one for
>> fixed and another for the non-fixed fields. Except for a unique id, I do not
>> store the fields in Lucene - i just index them. From the index, i get the
>> unique id which is all I care about. (the objects are stored elsewhere and
>> can be looked up based on this unique id).
>> I did try using a single indexer, but things were quite slow. Getting high
>> throughput is crucial and having two indexers seemed to do very well. (more
>> than twice as fast)
>> Further, the index will never be modified and I can have just one thread
>> writing to the index. If there are any other performance tips would be very
>> helpful. I have already looked at the wiki link regarding performance and
>> using some of them.
>> Thanks,
>> ~preetham
>>>> Now, I want to have boolean AND query's looking for values in both
>>>> indexes. Like f1=1234 AND f7=ABCD.f1 and f7 and present in two separate
>>>> indexes. Would using the MultiIndexReader help ? Since I am doing an AND,
>>>> dont expect that it would work.
>>>> Thanks,
>>>> ~preetham
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>>> --------------------------
>>> Grant Ingersoll
>>> Lucene Helpful Hints:
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