If the documents indexed in a container are spread across multiple document stores, changing the main index settings produces lesser performance gain compared to having all the documents in one document store.
omniq.index.term.useRootChildrenCache and omniq.lexicon.document.useRootChildrenCache are
set to true. Disabling these degrades performance.
omniq.index.term.numSegments index parameter has a greater impact on query performance, but will have lesser effect on indexing performance. The default setting is:
<SystemProperty name="omniq.index.term.numSegments" value="5"/>
The main index data is striped across each segment to reduce the Java RandomAccessFile seek time. For larger files, RandomAccessFile seek time gets progressively longer, so by having multiple segments, the overall index size is kept the same, but is split over multiple files. As file lengths are shorter, the seek times in each of the files gets reduced. Increasing the number of index segments increases the number of files handled, which impacts the JVM settings of the container.By default, the number of term index segments is set to 5. If you intend to index more than 250,000 documents in a document store, Sybase recommends increasing the number of term segments to, for example, 10.
For higher numbers of documents (above 500,000), setting
the number of index segments to a lower value can cause indexing
errors. Indexing more than 2 million documents in a single document
store requires 20 term index segments or more.
The second main index setting that can affect performance is omniq.lexicon.reverseDocument.numSegments. The default setting is:
<SystemProperty name="omniq.lexicon.reverseDocument.numSegments" value="4"/>
Increasing the number of reverse document lexicon segments slightly improves performance since it shares the data across more segments. The number of reverse document lexicon segment value must be a factor of the document maximum key length. For the default maximum document key length of 256, different document path lengths are split across 4 segments with lengths 0-64, 64-128, 128-196, and 196-256.
The number of reverse documents lexicon segment settings
applies only to file system document stores.
omniq.lexicon.document.maxKeyLength is the last main index setting parameters that has an impact on Sybase Search performance. The default setting is:
<SystemProperty name="omniq.lexicon.document.maxKeyLength" value="256"/>
If the source documents have document paths that are less than the default value, reducing maxKeyLength improves performance. When maxKeyLength is reduced, index lexicon files require less space to store the indexed document paths; because there is less data to read, access time is reduced.
The number of reverse documents lexicon segment settings
applies only to file system document stores.
