Generally, newer versions of dtSearch can search and update indexes created by older versions, going back to version 6.

File parser changes between versions may cause hit highlighting to appear incorrectly in retrieved documents when a different dtSearch version is used to search an index than was used to create the index. This is because dtSearch stores word offsets in the index, and when a file parser changes in a way that affects word counting, the same word offset may point to a different word when a newer file parser is used. 

In practice, this usually affects a very small percentage of documents with each minor update. When upgrading across many versions (for example, from version 7.22 to 7.64), a significant percentage of documents may be affected. 

To correct this, rebuild the index with the current dtSearch version. You can also use the flag dtsConvertAutoUpdateHits with FileConverter to have it automatically update the locations of hits to take into account any file parser changes or changes in the file since it was indexed.

dtSearch 7 supports a new index format, with higher capacity (up to 1 terabyte per index). In addition to higher capacity, the new format has some other advantages over the dtSearch 6 index format:

• Support for caching text in the index
• Faster indexing and searching
• Much faster incremental updates

dtSearch 7 can read and update indexes created with any of the dtSearch 6.x versions. To create an index in the old version 6 format, set the dtsIndexCreateVersion6 flag in IndexJob.IndexingFlags. 

The format of an index is automatically detected when the index is opened, so there is no need to specify when updating or searching an index what the format of the index is. 

dtSearch 6 generally cannot read version 7 indexes. 

Upgrading an index 

Compressing a version 6 index using version 7 of the dtSearch Engine will automatically convert the index to the version 7 format 

Beta notes 

Some dtSearch Engine 6.x versions had beta support for the version 7 index format, but only version 6.51 fully supports the final release version of the dtSearch 7 index format. Older versions of the dtSearch Engine should not be used with dtSearch 7 indexes. 

dtSearch 7 supports all of the interim versions of the dtSearch 7 index format that were used during beta testing. However, any indexes that were created with beta versions should be re-created with the release version of dtSearch 7, or at least compressed with version 7 to upgrade and optimize the index structure.

Building and Maintaining Indexes