[Hibernate] Plan for a full text search facility built on top of Hibernate Lucene annotations
After chatting with Emmanuel, here is a draft plan for a closer integration between Hibernate and Lucene for performing full text queries. Hibernate annotations for Lucene helps keeping the lucene indexes up to date, but doesn't provide a query facility. It also lacks converters that would for example help store a Date with the proper format in Lucene, so that the alphabetic order matches the Object's natural order. A framework like Compass ( http://www.opensymphony.com/compass ) is meant to fix this problem, by implementing it's own OSEM (Object, Search Engine Mapping), and having a query facility that mimics what hibernate is doing with database side. Compass can even reuse Hibernate's mapping thus minimizing the configuration effort. One short coming I've found with Compass though is that the objects that you get when you query the full text engine aren't connected to the ones in the database. So if you manipulate them, the changes aren't persisted or can actually erase some of the information in the database. The best way to have a simple and risk free integration is to build a Full Text query facility that would be closely integrated with Hibernate Hibernate Lucene annotations. So, querying the Full Text indexes would return objects, like Compass does, but those objects would be fetched from the database. Actually, for performance reasons, they could be initialized with the information from the FT index, and, through byte code enhancement, if an uninitialized property is read, or a property is set, the real object could be fetched from the database and read/set accordingly. Here are a few examples : 1) Just make a full text search : query toto would fetch all the object with an indexed field containing toto from the Lucene index. If the objects are initialized from the Lucene index, just one query to the Lucene index is done, and the search results can be displayed. = Best performance. Loading the objects from the database is useless here, and would only lead to poorer performances. 2) Make a full text search AND manipulate the objects : You want to query all the objects with toto, and increment their searchHits property. You do the query, with a Load.EAGER parameter. Only the objects' ids are retrieved from Lucene, and the real objects are retrieved from Hibernate 3) Mix both approaches Requires byte code enhancements. Can be useful for cases where for some types of objects you don't want to store all the properties required to display the search view results in the index. Only those objects will be loaded from Hibernate. All 3 modes should work, but we can always begin by implementing mode 2 only (retrieving only the id's from Lucene, and initializing the objects from Hibernate). Everything will still work, but performance will not be optimal. Later on we can implement mode 3 (which would also solve situation 1), and the changes will be transparent to the user. Only the performance will be better. Another advantage of integrating the Full Text query closely with Hibernate is that in some cases where a field isn't indexed but the query is still simple (fiels x like toto%), the Lucene index would not be needed, and some queries can be performed directly via Hibernate in a transparent way for the user. To summarize this, the biggest changes would be : - Add converters to Hibernate Lucene annotations, like what Compass is doing : http://www.opensymphony.com/compass/versions/0.9.1/html/core-settings.html#config-converter - Build a Full Text query facility similar to Hql / Criteria, but focussed on full text search (also like Compass's one : http://www.opensymphony.com/compass/versions/0.9.1/html/core-workingwithobjects.html#Searching ) but that would make sure the objects retrieved from the Lucene index behave as if they were retrieved from the database. I would be glad to ear from your feedback on this. Thanks, Sylvain. ___ hibernate-devel mailing list hibernate-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/hibernate-devel
Re: [Hibernate] Plan for a full text search facility built on top of Hibernate Lucene annotations
About the QL : You're right, the goal isn't to provide yet another QL, and Lucene's one should be used. I meant having a Criteria type of QL, like what Compass does :CompassQueryBuilder queryBuilder = session.createQueryBuilder(); CompassHits hits = queryBuilder.bool() .addMust( queryBuilder.term(name, jack) ) .addMustNot( queryBuilder.term(familyName, london) ) .toQuery() .addSort(familyName, CompassQuery.SortPropertyType.STRING) .addSort(birthdate, CompassQuery.SortPropertyType.INT) .hits(); More details here : http://www.opensymphony.com/compass/versions/0.9.1/html/core-workingwithobjects.html#Searching About the cache : You're probably right, but I don't know enough about this. I only know Compass also provides some cache. About the bytecode enhancement : This one is quite important. Support you have several types of Objects that have an report property, and you want to show all those documents containing the word toto in their report property. The best way is for the query facility to return a collection of those documents with their id report property set (which can be done only by getting the result from Lucene), without ever touching the SQL database. Forcing all those objects, that might be persisted in different tables, to be loaded by Hibernate would be both a performance killer and useless. But then, if you ever decide to do more than access one of the Lucene initialized property, you will need those documents to be loaded from Hibernate. This can only be done through some kind of wrapper / mock / byte enhancement, whatever you call it. This is what mixed mode means. You initialize the objects from the Lucene index, but later fetch the real persisted object from the database as needed, and in a transparent way for the user. As I said, in a first implementation, we can always fetch eager from Hibernate, but some provision should be made to avoid loading from the database when it's not necessary. If you use mostly the full text search to display search result pages, then most of the time, you'll never need to hit the database. Sylvain. On Thu, 2006-06-01 at 11:23 +0200, Max Rydahl Andersen wrote: All sounds cool ;) I can see the advantage of converters which can put elements into Lucence in a better/human manner. The loading of objects from Lucene + yet another QL I'm a bit more critical about. Would it not be better to do the following: 1. Use whatever QL Lucene supports to express the query. (What does another QL helps here ?) 2. Do the query against the Lucence index and return id's which then is resolved via Hibernate and possible in 2nd lvl cache. (We could maybe optimize the id lookups via some targetted queries) 3. IFF you really want look into have Lucene be a 2nd lvl cache provider ? (would probably require a chainable cacheprovider to have both lucence and ehcache queries in the same app...but that is sugar) ...maybe there is something I miss because I don't understand what the mixed mode means and why you want bytecode enhancement mixed in here ? /max After chatting with Emmanuel, here is a draft plan for a closer integration between Hibernate and Lucene for performing full text queries. Hibernate annotations for Lucene helps keeping the lucene indexes up to date, but doesn't provide a query facility. It also lacks converters that would for example help store a Date with the proper format in Lucene, so that the alphabetic order matches the Object's natural order. A framework like Compass ( http://www.opensymphony.com/compass ) is meant to fix this problem, by implementing it's own OSEM (Object, Search Engine Mapping), and having a query facility that mimics what hibernate is doing with database side. Compass can even reuse Hibernate's mapping thus minimizing the configuration effort. One short coming I've found with Compass though is that the objects that you get when you query the full text engine aren't connected to the ones in the database. So if you manipulate them, the changes aren't persisted or can actually erase some of the information in the database. The best way to have a simple and risk free integration is to build a Full Text query facility that would be closely integrated with Hibernate Hibernate Lucene annotations. So, querying the Full Text indexes would return objects, like Compass does, but those objects would be fetched from the database. Actually, for performance reasons, they could be initialized with the information from the FT index, and, through byte code enhancement, if an uninitialized property is read, or a property is set, the real object could be fetched from the database and read/set accordingly. Here are a few examples : 1) Just make a full text search : query toto would fetch all the object with an indexed field containing toto from the Lucene index. If the objects are initialized from the Lucene index, just one
Re: [Hibernate] Any timeframe for the resolution of ANN-1 (Map annotations support)
Ok, thanks, Sylvain. On Wed, 2006-04-12 at 11:54 +0200, Emmanuel Bernard wrote: (Subclass of) CollectionBinder is the area that will do the job And HbmBinder is the code to take inspiration from. Let me know if you've some annotation choice desing questions. Sylvain Vieujot wrote: Ok, thanks for your response. I'll dive into the code and try to come up with something. As I'm not familiar with that code yet, if you have any direction / advise, please do. It'll save me a lot of time. Thanks, Sylvain. On Wed, 2006-04-12 at 00:27 +0200, Emmanuel Bernard wrote: I'm very busy these days on some personal areas and on EJB3 compliance. So apart from a contributed patch, I can't see any quick resolution. I think Anthony is pretty busy too. Sylvain Vieujot wrote: Hello, We have moved a project that was hibernate+xdoclet based to hibernate annotations. We're pretty happy with it except that hibernate annotations still doesn't support maps of non-entities (bug ANN-1). When we started the migration we were quite confident it would be solved by now as it was marked to be solved in beta9. But now we start to be afraid this continues to slip and puts us in trouble. So, is there any fore-casted time-frame for this bug to be resolved ? Can we help in some way ? Is there a simple workaround that would be compatible with the standard hibernate mapping on the database side ? Thanks, Sylvain, --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ hibernate-devel mailing list hibernate-devel@lists.sourceforge.net mailto:hibernate-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/hibernate-devel --- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnkkid=110944bid=241720dat=121642 ___ hibernate-devel mailing list hibernate-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/hibernate-devel
[Hibernate] Any timeframe for the resolution of ANN-1 (Map annotations support)
Hello, We have moved a project that was hibernate+xdoclet based to hibernate annotations. We're pretty happy with it except that hibernate annotations still doesn't support maps of non-entities (bug ANN-1). When we started the migration we were quite confident it would be solved by now as it was marked to be solved in beta9. But now we start to be afraid this continues to slip and puts us in trouble. So, is there any fore-casted time-frame for this bug to be resolved ? Can we help in some way ? Is there a simple workaround that would be compatible with the standard hibernate mapping on the database side ? Thanks, Sylvain,
