I am developing an Azure based website and I want to provide search capabilities using Lucene. (structured json objects would be indexed and stored in Lucene and other content such as Word documents, etc. would be indexed in lucene but stored in blob storage) I want the search to be secure, such that one user would never see a document belonging to another user. I want to allow ad-hoc searches as typed by the user. Lastly, I want to query programmatically to return predefined sets of data, such as "all notes for user X". I think I understand how to add properties to each document to achieve these 3 objectives. (I am listing them here so if anyone is kind enough to answer, they will have better idea of what I am trying to do)
My questions revolve around performance and security.
Can I improve document security by having a separate index for each user, or is including the user's ID as a parameter in each search sufficient?
Can I improve indexing speed and total throughput of the system by having a separate index for each user? My thinking is that having separate indexes would allow me to scale the system by having multiple index writers (perhaps even on different server instances) working at the same time, each on their own index.
Any insight would be greatly appreciated.
Regards,
Nate
Of course, one index.
You can do even better than what you suggested by using ManifoldCF (Apache product that knows how to handle Solr) to manage security.
And one off topic, uninformed suggestion: I'd rather use CloudBees or Heroku (or Amazon) instead of Azure.
Until you will use several machines for indexing I guess it's more convenient to use single index. Lucene community done a lot of work to make indexing process as efficient as it can. So unless you intentionally want to implement distributed indexing I doesn't recommend you to split indexes.
However there are several reasons why you would want to split indexes:
if your machine have several IO devices which could be utilized in parallel. In this case, if you are IO bound, splitting indexes is good idea.
splitting document fields between indexes (this is what ParallelReader is supposed for). This is more exotic form of splitting, but it may be a good idea if search is performed using different groups of fields. Suppose, we have two search query types: the first is using field name and type, and the second is using fields price and discount. If those fields are updated at different rate (I guess, name updates are far more rarely than price updates), updating only part of index would require less IO resources. This will give more overall throughput to the system.
Related
We are interested in using DocumentDb as a data store for a number of data sources and as such we are running a quick POC to establish whether it meets the criteria we are looking for.
One of the areas we are keen to provide is look ahead search capabilities for certain fields. These are traditionally provided using the SQL LIKE syntax which does not appear to be supported at present.
Searching online I have seen people talking about integrating Azure search but this appears to be a very costly mechanism for such a simple use case.
I have also seen people mention the use of UDF's but this appears to require an entire collection scan which is not practical from a performance perspective.
Does anyone have any alternative suggestions? One thing I considered was simply using a SQL table and initiating an update each time a document was inserted\updated\deleted?
DocumentDB supports STARTSWITH and range indexes to support prefix/look ahead searching.
You can progressively make queries like the following based on what your user types in a text box:
SELECT TOP 10 * FROM hotel H WHERE STARTSWITH(H.name, "H")
SELECT TOP 10 * FROM hotel H WHERE STARTSWITH(H.name, "Hi")
SELECT TOP 10 * FROM hotel H WHERE STARTSWITH(H.name, "Hil")
SELECT TOP 10 * FROM hotel H WHERE STARTSWITH(H.name, "Hilton")
Note that you must configure the collection, or the path/property you're using for these queries with a range index. You can extend this approach to handle additional cases as well:
To query in a case-insensitive manner, you must store the lower case form of the search property, and use that for querying.
I faced a similar situation, where a fast lookup was required, as a user typed search terms.
My scenario was that potentially thousands of simultaneous users would be performing such lookups; when testing this under load, to avoid saturation and throttling, we found we would have to increase the DocumentDB Request Unit (RU) throughput amount to a point that was not financially viable for us, in our specific circumstances.
We decided that DocumentDB was best used as the persistent store, and 'full' data retrieval - and this role it performs exceptionally well - while a small ElasticSearch cluster performed the role it was designed for - text search, faceted search, weighted search, stemming, and most relevant to your question, autocomplete analyzersand completion suggesters.
The subject of type ahead queries, creation of indexes, autocomplete analyzer and query time 'search as you type' in ElasticSearch can be found here, here and here
The fact that you plan to have several data sources would also potentially make the ElasticSearch cluster approach more attractive, to aggregate search data.
I used the Bitnami template available in the Azure market place to create relatively small instances, and most importantly, this allowed me to place the cluster on the same Virtual Network as my other components, which greatly increased performance.
Cost was lower than Azure Search (which uses ElasticSearch under the hood).
We've got 50,000,000 (and growing) documents which we want to be able to search.
Each "document" is in reality a page of a larger document, but the granularity required is at the page level.
Each document therefore has a few bits of metadata (e.g., which larger document it belongs to)
We originally built this using Sphinx which has served quite well, but is getting slow, despite having quite generous hardware thrown at it (via Amazon AWS).
There are new requirements coming through that mean we have to be able to pre-filter the database before searching, i.e. to search only a subset of the 50M documents based on some aspect of the metadata (e.g., "search only documents added in the last 6 months", or "search only these documents belonging to this arbitrary list of parent documents")
One significant requirement is that we group search results by parent document, e.g. to return only the first match in a parent document in order to show the user a wider range of parent documents that match in the first page of results, rather than loads of matches in the first parent document followed by loads of matches in the second, etc. We would then give the user the option to search pages within only one specific parent document.
The solution doesn't have to be "free" and there is a bit of budget to spend.
The content is sensitive and needs to be protected so we can't simply let Google index it for us, at least not in any way that would allow the general public to come across it.
I've looked at using Sphinx with even more resources (putting an index of 50M documents into memory is sadly not an option within our budget) and I've looked at Amazon CloudSearch but it seems that we'd have to spend >$4k per month and that's beyond the budget.
Any suggestions? Something deployable within AWS is a bonus. I'm aware that we may be asking for the unobtainable but if you think that's the case, please say so (and give reasons!)
50M docs sounds like quite a feasible task for Sphinx.
We originally built this using Sphinx which has served quite well, but is getting slow, despite having quite generous hardware thrown at it (via Amazon AWS).
I second the comment above suggesting sharding. Sphinx allows you to split a big index into several shards, each served by its own agent. You can run the agents on the same server or distribute them across multiple AWS instances.
There are new requirements coming through that mean we have to be able to pre-filter the database before searching, i.e. to search only a subset of the 50M documents based on some aspect of the metadata
Assuming these metafields are indexed as attributes, you can add SQL-alike filters to every search query (e.g. doc_id IN (1,2,3,4) AND date_created > '2014-01-01').
One significant requirement is that we group search results by parent document
You can group by any attribute.
Should I be generating the id of the documents in a CouchDB or should I depend on CouchDB to generate it? What are the advantages or disadvantages in these approaches? Is there any performance implications on any of these options?
There is no difference as far as CouchDB is concerned. Frederick is right that sequential ids are slightly faster. If you query /_uuids?count=10 you will notice that the UUIDs are sequential (by default).
However, even with random IDs, once you run compaction, they will all be in the "right" order internally in the .couch file and at that point there is no difference. So in the long run, I don't usually worry about it.
The main thing is that you should use mostly sequential ids. As this article and this bit of the couchdb book explain, using random ids results in a much less efficient structure internally, both speed wise and in terms of space used on disc.
Self generated ids are almost impossible to deal with if you have two or more separated instances of your app. Because the synchronisation between the different instances is not instantaneous. A solution for this can be to have one server dedicated to generate (or check the availability of) the ids, for example using a SQL database, and acting as a gate for document creation.
On the other hand, if you have only one server and will never need more, there is one advantage I find interesting to self generated uids: since they have to be unique, you can use them in urls. For instance take the slug of the title of a blog post as the _id.
Performance-wise, the CouchDB's generated ids are pretty long so if your own ids are shorter, you will save significant disk space (assuming you have a looot of documents).
Both answers above tell about PROS of sequential IDs.
Here is a major problem arose by sequential IDs.
Predictability of other IDs in documents using a single ID.
Due to this we can't use sequential IDs in application URLs as identifiers due to other IDs being predictable using one ID, and using as url authentication is also not possible.( As done by file sharing services).
I am building a tool that searches people based on a number of attributes. The values for these attributes are scattered across several systems.
As an example, dateOfBirth is stored in a SQL Server database as part of system ABC. That person's sales region assignment is stored in some horrible legacy database. Other attributes are stored in a system only accessible over an XML web service.
To make matters worse, the the legacy database and the web service can be really slow.
What strategies and tips should I consider for implementing a search across all these systems?
Note: Although I posted an answer, I'm not confident its a great answer. I don't intend to accept my own answer unless no one else gives better insight.
You could consider using an indexing mechanism to retrieve and locally index the data across all the systems, and then perform your searches against the index. Searches would be an awful lot faster and more reliable.
Of course, this just shifts the problem from one part of your system to another - now your indexing mechanism has to handle failures and heterogeneous systems, but that may be an easier problem to solve.
Another factor is how often the data changes. If you have to query data in real-time that goes stale very quickly, then indexing may not be practical.
If you can get away with a restrictive search, start by returning a list based on the search criteria corresponding to the fastest data source. Then join up those records with the other systems and remove records which don't match the search criteria.
If you have to implement OR logic, this approach is not going to work.
While not an actual answer, this might at least get you partway to a workable solution. We had a similar situation at a previous employer - lots of data sources, different ways of accessing those data sources, different access permissions, military/government/civilian sources, etc. We used Mule, which is built around the Enterprise Service Bus concept, to connect these data sources to our application. My details are a bit sketchy, as I wasn't the actual implementor, just an integrator, but what we did was define a channel in Mule. Then you write a simple integration piece to go between the channel and the data source, and the application and the channel. The integration piece does the work of making the actual query, and formatting the results, so we had a generic SQL integration piece for accessing a database, and for things like web services, we had some base classes that implemented common functionality, so the actual customization of the integration piecess was a lot less work than it sounds like. The application could then query the channel, which would handle accessing the various data sources, transforming them into a normalized bit of XML, and return the results to the application.
This had a lot of advantages for our situation. We could include new data sources for existing queries by simply connecting them to the channel - the application didn't have to know or care what data sources where there, as it only looked at the data from the channel. Since data can be pushed or pulled from the channel, we could have a data source update the application when, for example, it was updated.
It took a while to get it configured and working, but once we got it going, we were pretty successful with it. In our demo setup, we ended up with 4 or 5 applications acting as both producers and consumers of data, and connecting to maybe 10 data sources.
Have you thought of moving the data into a separate structure?
For example, Lucene stores data to be searched in a schema-less inverted indexed. You could have a separate program that retrieves data from all your different sources and puts them in a Lucene index. Your search could work against this index and the search results could contain a unique identifier and the system it came from.
http://lucene.apache.org/java/docs/
(There are implementations in other languages as well)
Have you taken a look at YQL? It may not be the perfect solution but I might give you starting point to work from.
Well, for starters I'd parallelize the queries to the different systems. That way we can minimize the query time.
You might also want to think about caching and aggregating the search attributes for subsequent queries in order to speed things up.
You have the option of creating an aggregation service or middleware that aggregates all the different systems so that you can provide a single interface for querying. If you do that, this is where I'd do the previously mentioned cache and parallize optimizations.
However, with all of that it you will need weighing up the development time/deployment time /long term benefits of the effort against migrating the old legacy database to a faster more modern one. You haven't said how tied into other systems those databases are so it may not be a very viable option in the short term.
EDIT: in response to data going out of date. You can consider caching if your data if you don't need the data to always match the database in real time. Also, if some data doesn't change very often (e.g. dates of birth) then you should cache them. If you employ caching then you could make your system configurable as to what tables/columns to include or exclude from the cache and you could give each table/column a personalizable cache timeout with an overall default.
Use Pentaho/Kettle to copy all of the data fields that you can search on and display into a local MySQL database
http://www.pentaho.com/products/data_integration/
Create a batch script to run nightly and update your local copy. Maybe even every hour. Then, write your query against your local MySQL database and display the results.
I am just wondering if we could achieve some RDBMS capabilities in lucene.
Example:
1) I have 10,000 project documents (pdf files) which have to be indexed with their content to make them available for search.
2) Every document is related to a SINGLE PROJECT. The project can contain details like project name, number, start date, end date, location, type etc.
I have to search in the contents of the pdf files for a given keyword, but while displaying the results I want to display the project meta data as mentioned in point (2).
My idea is to associate a field called projectId with each pdf file while indexing. Once we get that, we will fire search again for getting project meta data.
This way we could avoid duplicated data. Also, if we want to update the project meta data we will end up updating at a SINGLE PLACE only. Otherwise if we store this meta data with all the pdf doument indexes, we will end up updating all of the documents, which is not the way I am looking for.
please advise.
If I understand you correctly, you have two questions:
Can I store a project id in Lucene and use it for further searches? Yes, you can. This is a common practice.
Can I use this project id to search Lucene for project meta data? Yes, you can. I do not know if this is a good idea. It depends on the frequency of your meta data updates and your access pattern. If the meta data is relatively static, and you only access it by id, Lucene may be a good place to store it. Otherwise, you can use the project id as a primary key to a database table, which could be a better fit.
Sounds like a perfectly good thing to do. The only limitation you'll have (by storing a reference to the project in Lucene rather than the project data itself) is that you won't be able to query both the document text and project metadata at the same time. For example, "documentText:foo OR projectName:bar" . If you have no such requirement, then seems like storing the ID in Lucene which refers to a database row is a fine thing to do.
I am not sure on your overall setup, but maybe Hibernate Search is for you. It would allow you to combine the benefits of a relational database with the power of a fulltext search engine like Lucene. The meta data could live in the database, maybe together with the original pdf documents, while the Lucene documents just contain the searchable data.
This is definitely possible. But always be aware of the fact that you're using Lucene for something that it was not intended for. In general, Lucene is designed for full-text search, not for mapping relational content. So the more complex your system your relational content becomes, the more you'll see a decrease in performance.
In particular, there are a few areas to keep a close eye on:
Storing the value of each field in your index will decrease performance. If you are not overly concerned with sub-second search results, or if your index is relatively small, then this may not be a problem.
Also, be aware that if you are not using the default ranking algorithm, and your custom algorithm requires information about the project in order to calculate the score for each document, this will have a dramatic impact on search performance, as well.
If you need a more powerful index that was designed for relational content, there are hierarchical indexing tools out there (one developed by Apache, called Jackrabbit) that are worth looking into.
As your project continues to grow, you might also check out Solr, also developed by Apache, which provides some added functionality, such as multi-faceted search.
You can use Lucene that way;
Pros:
Full-text search is easy to implement, which is not the case in an RDBMS.
Cons:
Referential integrity: you get it for free in an RDBMS, but in Lucene, you must implement it yourself.