I want to know if there is any way to perform wildcard searches in cassandra database.
e.g.
select KEY,username,password from User where username='\*hello*';
Or
select KEY,username,password from User where username='%hello%';
something like this.
There is no native way to perform such queries in Cassandra. Typical options to achieve the same are
a) Maintain an index yourself on likely search terms. For example, whenever you are inserting an entry which has hello in the username, insert an entry in the index column family with hello as the key and the column value as the key of your data entry. While querying, query the index CF and then fetch data from your data CF. Of course, this is pretty restrictive in nature but can be useful for some basic needs.
b) A better bet is to use a full text search engine. Take a look at Solandra, https://github.com/tjake/Solandra or Datastax enterprise http://www.datastax.com/products/enterprise
This project also looks promising
http://tuplejump.github.io/stargate/
I have not looked deeply at it recently, but when I last evaluated it, it looked promising.
Related
I have a problem where there is a huge list of strings or phrases it might scale from 100,000 to 100Million. when i search for a phrase if found it gives me the Id or index to database for further operation. I know hash table can be used for this, but i am looking for other algorithm which could serve me to generate index based on strings and can also be useful in some other features like autocomplete etc.
I read suffix tree/array based on some SO threads they serve the purpose but consumes alot memory than i can afford. Any alternatives to this?
Since my search is only in a huge list of millions of strings. No docs no webpages not interested in search engine like lucene etc.
Also read about inverted index sounds helpful but which algorithm i need to study for it?.
If this Database index is within MS SQL Server you may get good results with SQL Full Text Indexing. Other SQL providers may have a similar function but I would not be able to help with those.
Check out: http://www.simple-talk.com/sql/learn-sql-server/understanding-full-text-indexing-in-sql-server/
and
http://msdn.microsoft.com/en-us/library/ms142571.aspx
I am currently thinking how to best store web-crawling results in a database. In another question document-oriented databases were recommended to use for a web-crawler project: Database for web crawler in python?
Now I am wondering if map/reduce is the right way for such classification and value-generation. At least it seems to be able to do such stuff (map for only classification like years or authors, and map/reduce for calculating numerical values which I cannot think of an example at the moment).
However, would map-reduce / DocumentStores also be able to give me the right documents for a given word? In a relational database I would have to use a JOIN on some tables and then get documents containing these words:
SELECT * FROM docs d
JOIN doc_words dw ON dw.doc_id = d.id
JOIN words w ON dw.word_id = w.id
WHERE w.word = 'foo'
I guess DocumentStores are not capable of such an operation as they do not support fulltext index and are not intended to have many references / relations.
Would the better alternative be mixing several systems? E.g. one for searching by words, one for searching by different values if present (like year of publication, author, …)? I think DocumentStores are not so bad for storing the metadata, as sometimes there are specific values and sometimes not (and DocumentStores are easy to use across multiple servers if wanted, as soon as there are too many documents for one server). Yet, I am not sure what would the best way to implement searching for a collection of documents (including webpages, pdfs, images, which have always different meta-data, but often also need fulltext index).
To make a clear question: Should I use another database system together with DocumentStores, use DocumentStores alone (howto search for words quickly?) or another DB system alone?
PS: Another example for such a problem would be the linking between webpages, which cannot be saved in DocumentStores well either. However, OrientDB might solve this problem as it seems to combine graph database and document-oriented database.
Checkout RavenDB. It is a document DB with Map/Reduce queries, using Lucene under the hood, so full-text search is fully supported also within Map/Reduce queries.
Custom Lucene analyzers are supported as well, so there's a lot of room for further full-text extensions.
Other features like Includes and Live Projections may give you everything else a simple Map/Reduce will be missing.
See MarkLogic - which was designed specifically for searching documents. http://developer.marklogic.com/products/marklogic-server/which-nosql
i need to do something like this on apache cassandra,
SELECT * FROM mytable where address = "%indonesia%"
any idea how to do it on cassandra?
Its not supported out of the box. You must maintain your own indices.
I would recommend to use "Supercolumn index" or use a order preserving partitioner (e.g. org.apache.cassandra.dht.OrderPreservingPartioner) in conjunction with range queries.
Take a look at the slides from Benjamin Black's excellent talk about cassandra and index
Just to add to what Schildmeijer has said, unless you do a lot of extra work, you're probably not going to get the equivalent of an "%indonesia%" wildcard search in Cassandra. Much easier will be "indonesia%" or "%indonesia" (or "aisenodni%") using a range query on a special index that you've created for searches like this. The slides that Schildmeijer links to describe how to set up this kind of search at a high level.
If you're looking for full text search in blocks of text that are being stored in Cassandra, you might look into something like Lucene to maintain an index that can be used for doing certain kinds of searches over strings in the text. I am not too familiar with the details, but following are two links that might be helpful here:
http://github.com/tjake/Lucandra
http://lucene.apache.org/java/docs/index.html
We are searching disparate data sources in our company. We have information in multiple databases that need to be searched from our Intranet. Initial experiments with Full Text Search (FTS) proved disappointing. We've implemented a custom search engine that works very well for our purposes. However, we want to make sure we are doing "the right thing" and aren't missing any great tools that would make our job easier.
What we need:
Column search
ability to search by column
we flag which columns in a table are searchable
Keep some relation between db column and data
we provide advanced filtering on the results
facilitates (amazon style) filtering
filter provided by grouping of results and allowing user to filter them via a checkbox
this is a great feature, users like it very much
Partial Word Match
we have a lot of unique identifiers (product id, etc).
the unique id's can have sub parts with meaning (location, etc)
or only a portion may be available (when the user is searching)
or (by a decidedly poor design decision) there may be white space in the id
this is a major feature that we've implemented now via CHARINDEX (MSSQL) and INSTR (ORACLE)
using the char index functions turned out to be equivalent performance(+/-) on MSSQL compared to full text
didn't test on Oracle
however searches against both types of db are very fast
We take advantage of Indexed (MSSQL) and Materialized (Oracle) views to increase speed
this is a huge win, Oracle Materialized views are better than MSSQL Indexed views
both provide speedups in read-only join situations (like a search combing company and product)
A search that matches user expectations of the paradigm CTRL-f -> enter text -> find matches
Full Text Search is not the best in this area (slow and inconsistent matching)
partial matching (see "Partial Word Match")
Nice to have:
Search database in real time
skip the indexing skip, this is not a hard requirement
Spelling suggestion
Xapian has this http://xapian.org/docs/spelling.html
Similar to google's "Did you mean:"
What we don't need:
We don't need to index documents
at this point searching our data sources are the most important thing
even when we do search documents, we will be looking for partial word matching, etc
Ranking
Our own simple ranking algorithm has proven much better than an FTS equivalent.
Users understand it, we understand it, it's almost always relevant.
Stemming
Just don't need to get [run|ran|running]
Advanced search operators
phrase matching, or/and, etc
according to Jakob Nielsen http://www.useit.com/alertbox/20010513.html
most users are using simple search phrases
very few use advanced searches (when it's available)
also in Information Architecture 3rd edition Page 185
"few users take advantage of them [advanced search functions]"
http://oreilly.com/catalog/9780596000356
our Amazon like filtering allows better filtering anyway (via user testing)
Full Text Search
We've found that results don't always "make sense" to the user
Searching with FTS is hard to tune (which set of operators match the users expectations)
Advanced search operators are a no go
we don't need them because
users don't understand them
Performance has been very close (+/1) to the char index functions
but the results are sometimes just "weird"
The question:
Is there a solution that allows us to keep the key value pair "filtering feature", offers the column specific matching, partial word matching and the rest of the features, without the pain of full text search?
I'm open to any suggestion. I've wondered if a document/hash table nosql data store (MongoDB, et al) might be of use? ( http://www.mongodb.org/display/DOCS/Full+Text+Search+in+Mongo ). Any experience with these is appreciated.
Again, just making sure we aren't missing something with our in-house customized version. If there is something "off the shelf" I would be interested in it. Or if you've built something from some components, what components (search engines, data stores, etc) did you use and why?
You can also make your point for FTS. Just make sure it meets the requirements above before you say "just use Full Text Search because that's the only tool we have."
I ended up coding my own.
The results are fantastic. Users like it, it works well with our existing technologies.
It really wasn't that hard. Just took some time.
Features:
Faceted search (amazon, walmart, etc)
Partial word search (the real stuff not full text)
Search databases (oracle, sql server, etc) and non database sources
Integrates well with our existing environment
Maintains relations, so I can have a n to n search and display
--> this means I can display child records of a master record in search results
--> also I can search any child field and return the master record
It's really amazing what you can do with dictionaries and a lot of memory.
I recommend looking into Solr, I believe it will meet you needs:
http://lucene.apache.org/solr/
For an off-she-shelf solution: Have you checked out the Google Search Appliance?
Quote from the Google Mini/GSA site:
... If direct database indexing is a requirement for you, we encourage you to consider the Google Search Appliance, which has direct database connectivity.
And of course it indexes everything else in the Googly manner you'd expect it to.
Apache Solr is a good way to start your project with and it is open source . You can also try Elastic Search and there are a lot of off shelf products which offer good customization abilities and search features such as Coveo, SharePoint Fast, Google ...
I am trying to visualize how to create a search for an application that we are building. I would like a suggestion on how to approach 'searching' through large sets of data.
For instance, this particular search would be on a 750k record minimum table, of product sku's, sizing, material type, create date, etc;
Is anyone aware of a 'plugin' solution for Coldfusion to do this? I envision a google like single entry search where a customer can type in the part number, or the sizing, etc, and get hits on any or all relevant results.
Currently if I run a 'LIKE' comparison query, it seems to take ages (ok a few seconds, but still), and it is too long. At times making a user sit there and wait up to 10 seconds for queries & page loads.
Or are there any SQL formulas to help accomplish this? I want to use a proven method to search the data, not just a simple SQL like or = comparison operation.
So this is a multi-approach question, should I attack this at the SQL level (as it ultimately looks to be) or is there a plug in/module for ColdFusion that I can grab that will give me speedy, advanced search capability.
You could try indexing your db records with a Verity (or Solr, if CF9) search.
I'm not sure it would be faster, and whether even trying it would be worthwhile would depend a lot on how often you update the records you need to search. If you update them rarely, you could do an Verity Index update whenever you update them. If you update the records constantly, that's going to be a drag on the webserver, and certainly mitigate any possible gains in search speed.
I've never indexed a database via Verity, but I've indexed large collections of PDFs, Word Docs, etc, and I recall the search being pretty fast. I don't know if it will help your current situation, but it might be worth further research.
If your slowdown is specifically the search of textual fields (as I surmise from your mentioning of LIKE), the best solution is building an index table (not to be confiused with DB table indexes that are also part of the answer).
Build an index table mapping the unique ID of your records from main table to a set of words (1 word per row) of the textual field. If it matters, add the field of origin as a 3rd column in the index table, and if you want "relevance" features you may want to consider word count.
Populate the index table with either a trigger (using splitting) or from your app - the latter might be better, simply call a stored proc with both the actual data to insert/update and the list of words already split up.
This will immediately drastically speed up textual search as it will no longer do "LIKE", AND will be able to use indexes on index table (no pun intended) without interfering with indexing on SKU and the like on the main table.
Also, ensure that all the relevant fields are indexed fully - not necessarily in the same compund index (SKU, sizing etc...), and any field that is searched as a range field (sizing or date) is a good candidate for a clustered index (as long as the records are inserted in approximate order of that field's increase or you don't care about insert/update speed as much).
For anything mode detailed, you will need to post your table structure, existing indexes, the queries that are slow and the query plans you have now for those slow queries.
Another item is to enure that as little of the fields are textual as possible, especially ones that are "decodable" - your comment mentioned "is it boxed" in the text fields set. If so, I assume the values are "yes"/"no" or some other very limited data set. If so, simply store a numeric code for valid values and do en/de-coding in your app, and search by the numeric code. Not a tremendous speed improvement but still an improvement.
I've done this using SQL's full text indexes. This will require very application changes and no changes to the database schema except for the addition of the full text index.
First, add the Full Text index to the table. Include in the full text index all of the columns the search should perform against. I'd also recommend having the index auto update; this shouldn't be a problem unless your SQL Server is already being highly taxed.
Second, to do the actual search, you need to convert your query to use a full text search. The first step is to convert the search string into a full text search string. I do this by splitting the search string into words (using the Split method) and then building a search string formatted as:
"Word1*" AND "Word2*" AND "Word3*"
The double-quotes are critical; they tell the full text index where the words begin and end.
Next, to actually execute the full text search, use the ContainsTable command in your query:
SELECT *
from containstable(Bugs, *, '"Word1*" AND "Word2*" AND "Word3*"')
This will return two columns:
Key - The column identified as the primary key of the full text search
Rank - A relative rank of the match (1 - 1000 with a higher ranking meaning a better match).
I've used approaches similar to this many times and I've had good luck with it.
If you want a truly plug-in solution then you should just go with Google itself. It sounds like your doing some kind of e-commerce or commercial site (given the use of the term 'SKU'), So you probably have a catalog of some kind with product pages. If you have consistent markup then you can configure a google appliance or service to do exactly what you want. It will send a bot in to index your pages and find your fields. No SQl, little coding, it will not be dependent on your database, or even coldfusion. It will also be quite fast and familiar to customers.
I was able to do this with a coldfusion site in about 6 hours, done! The only thing to watch out for is that google's index is limited to what the bot can see, so if you have a situation where you want to limit access based on a users role or permissions or group, then it may not be the solution for you (although you can configure a permission service for Google to check with)
Because SQL Server is where your data is that is where your search performance is going to be a possible issue. Make sure you have indexes on the columns you are searching on and if using a like you can't use and index if you do this SELECT * FROM TABLEX WHERE last_name LIKE '%FR%'
But it can use an index if you do it like this SELECT * FROM TABLEX WHERE last_name LIKE 'FR%'. The key here is to allow as many of the first characters to not be wild cards.
Here is a link to a site with some general tips. https://web.archive.org/web/1/http://blogs.techrepublic%2ecom%2ecom/datacenter/?p=173