Search technology has improved considerably over the years since Joomla was first launched and yet the standard, basic search component has not changed much over that time. It is still very crude and lacks the kind of search features that web users have come to expect, especially given the prevalence of advanced search engines such as Google. Smart Search allows you to incorporate some of those more advanced search features into your website.
Generally, if you have a type of content that is not handled by the core Joomla components, and you want to give your site visitors the opportunity to search that content, then you will need to write a Smart Search plug-in to support it. For example, suppose you have a component that stores information about different animal species. The component maintains a database table containing fields such as scientific name, vernacular name, classification and a description. Then you will need to create a plug-in that will tell the Smart Search indexer how to index the data in that table. As well as indexing individual words and phrases, you can also have the plug-in add each record to a content map, which might in this case include the kingdom, phylum, class, order and family. Content maps can then be used to filter search results.
Yes, this is fully supported by Smart Search itself. Indeed, you can use whatever user interface you care to devise for the filters. Just take a look at the code provided in the standard front-end module and component and you will see how you need to do it.
If you are changing content on your site frequently then you will need to run the indexer periodically to tidy-up the index. This is because deleting unused terms and phrases from the index is not currently handled automatically on-the-fly. This can be done manually from the Administrator or using the command-line indexer (which can be set up as a cron job to be run automatically).
Large sites may be better off with a dedicated standalone search engine, such as Solr, rather than the pure-PHP implementation used in Smart Search. In this first iteration of advanced search in Joomla it is likely that issues relating to scaling and performance will be revealed. There is also the potential for race conditions to occur when updating the index on frequent content changes. These issues are expected to be addressed more fully in Joomla 3.x.
Smart Search adds quite a few new tables to a Joomla installation, including 16 "mapping tables". These mapping tables resolve the many-to-many relationship between search terms and the content items that contain them. In theory those 16 tables could be merged into a single table and doing so would have negligible impact on small sites. However, on larger sites there would be a substantial impact on performance because the mapping table would have a very large number of entries and updating such a large table can be time-consuming.
Maintaining a search term index requires a fair amount of disk space, which increases the more terms that content items contain. Since phrases are also indexed, the longer the phrases, the more disk space required. For Smart Search in Joomla 2.5 the maximum length of a phrase has been fixed at 3 terms as a reasonable compromise between search usability and disk space usage. It is likely that this will be a parameter that can be tuned in a future version of search, probably starting in Joomla 3.0.
It is perhaps surprising that the number of entries in each of the mapping tables is not even roughly the same. Surely performance would be improved with uniform distribution? Actually no, there is a trade-off between insertion performance and search performance with a uniform distribution being good for the former but poor for the latter. This is an area of ongoing research with the number of tables and the distribution algorithm subject to change in the light of experience.
This is just a convenience that makes it easier to enable or disable all the Smart Search plug-ins with a single operation. This was considered desirable because Smart Search is not enabled by default in Joomla 2.5. It is likely that plug-ins will not be required at all when we move to search in Joomla 3.x.
Smart Search uses its own events, such as onFinderContentAfterSave, rather than the generic equivalent onContentAfterSave, purely as a convenience to make it easy to enable or disable Smart Search indexing by enabling/disabling a single plug-in.
Because Joomla 2.5 is the last in the 1.x/2.x series it must maintain a high degree of backwards-compatibility with the previous release in the series. As Smart Search is something entirely new and does not bear any resemblance to the regular search component of this or earlier releases it was considered important that users upgrading from those earlier versions would not be forced to change the way search works on their sites. Indeed, activation of Smart Search is something that should be done in a carefully considered way.
The focus of the present version of Smart Search was in moving code from the old JXtended Finder component into the latest version of Joomla. As that code was already considered stable and there was only a short window of opportunity to port the code over, it was felt that a major redevelopment of Finder was out of scope for the Joomla 2.5 release. Consequently, the code uses plug-ins to avoid any changes to the core CMS code, rather than developing a proper search API. We will definitely be looking to create such an API for the next iteration of Joomla.
Yes. The advanced search available from the search results page and the smart search module provide an example of how you can filter search results to produce facetted search. There is nothing stopping you from creating your own variations on these basic ideas. For example, you could change the simple drop-downs to accept multiple selections, or you could replace the drop-downs with an array of checkboxes.
The old Joomla search used a very primitive method of searching which relied on the FULLTEXT search provided by the database. This was very inefficient but provided a simple means of handling wildcard search queries. Smart Search provides an autocompletion feature which is effectively a wildcard search of terms in the index, but full wildcard searching is not supported due to the potential for crippling the server if the feature were to be abused. In most cases wildcard searching is used to cater for variations in a search term. For example, searching for "juggl*" in order to catch references to "juggling" as well as "juggler". Smart Search attempts to avoid the need for wildcard searching by instead supporting word stemming where words that have the same stem are considered equivalent so that searching for "juggler" will also retrieve instances of "juggling" without the need to use wildcards.
Yes, but there are still some issues to be resolved, especially regarding support for Asian languages.
If you use Smart Search on a multi-lingual site and come across any issues, please report them on the tracker so that we can better understand the problems that need to be resolved.
No. You will need to update Finder plug-ins to work with Smart Search. However, the changes should not be difficult to implement and in most cases will result in significantly less code. If you take a look at the current Smart Search plug-ins you should see that updating a Finder plug-in is pretty straightforward.