Lucene in Action

...In this section, we cover three closely related topics: concurrent index access, thread-safety of IndexReader and IndexWriter, and the locking mechanism that Lucene uses to prevent index corruption. These issues are often misunderstood by users new to Lucene. Understanding these topics is important, because it will eliminate surprises that can result when your indexing application starts serving multiple users simultaneously or when it has to deal with a sudden need to scale by parallelizing...

... simultaneously. Lucene's concurrency rules are simple but should be strictly followed: Any number of read-only operations may be executed concurrently. For instance, multiple threads or processes may ... IndexReader at a time. Based on these concurrency rules, we can create a more comprehensive set of examples, shown in table 2.2. These rules represent the allowed and disallowed concurrent operations on a single index. Table 2.2 Examples of allowed and disallowed concurrent operations performed...

...This chapter has given you a solid understanding of how a Lucene index oper- ates. In addition to adding Documents to an index, you should now be able to remove and update indexed Documents as well as manipulate a couple of index- ing factors to fine-tune several aspects of indexing to meet your needs. The knowledge about concurrency, thread-safety, and locking is essential if you're using Lucene in a multithreaded application or a multiprocess system. By now you should be dying to learn how...

...This chapter covers Performing basic index operations Boosting Documents and Fields during indexing Indexing dates, numbers, and Fields for use in sorting search results Using parameters that affect Lucene's indexing performance and resource consumption Optimizing indexes Understanding concurrency, multithreading, and locking issues in the context of indexing 28 So you want to search files stored ... that Lucene employs to prevent concurrent index modification....

... for Clustering Data. Prentice Hall. Lea, Doug. 2003. Overview of package util.concurrent Release 1.3.4. http:/ /gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html. Manning, Christopher...

..., it can also perform load tests by simulating a number of concur- rent users. The same decorator ... , which executes the TimedTest 10 times concurrently. SearchLoadTest executes testSearchByDay() 10 times concurrently, with each thread required to execute in under 100 milliseconds. It should ... , since it fails even the SearchTimedTest. The timings of each SearchTest, run as 10 concurrent tests ... the 100-millisecond requirement, even running under concurrent load....

... close the IndexWriter instance that opened that same index before. The concurrency matrix in the table ... , as you saw in section 2.2.4 Table 2.3 Concurrency matrix when the same instance of IndexWriter ... IndexReader oper- ation is in progress. You can think of these Lucene concurrency rules as analogous ... misuse and even misunderstanding of concurrency issues, so it uses a locking mechanism to do its best...

... Query Handler and each Index Searcher. There are many concurrent threads on the Query Handler side, any...

...Related to the concurrency issues in Lucene is the topic of locking. To prevent index corruption from misuse of its API, Lucene creates file-based locks around all code segments that need to be executed by a single process at a time. Each index has its own set of lock files; by default, all lock ... from concurrently attempting to modify an index. More precisely, the write.lock is obtained ... of Lucene sometimes don't have a good understanding of the concurrency issues described in this section...

... about concurrent index modification. An index should be modified by only a single operating system ... to try to prevent this type of concurrent index modification. When to optimize Although an index...

... is occurring concurrently with searching, newer documents indexed won't be visible to searches. In order... [Full sample chapter]

... of Doug Lea's util.concurrent package. The queue- based architecture easily scales to multiple machines...

...QueryParser rears its ugly head again with our changed date format. The built-in date-range handling parses DateFormat.SHORT formats into the DateField text conversions. It would be nice to let users enter a typical date format like 1/1/04 and have it converted to our revised date format of YYYYMMDD. This can be Figure 6.3 Performance test results for 10 concurrent SearchTests, each required to complete in 100 milliseconds or less done in a similar fashion to what we did in section 6.3.3 to pad...

.../otis/PDFs /tmp/pdfindex Indexing PDF document: /home/otis/PDFs/Concurrency-j-jtp07233.pdf Indexing...

... 297 compound format 341 updating documents 36 compound index 399-400 batching 37 K concurrency rules...