AJAX autocomplete is fairly simple to implement. However, I wonder how to handle smart tag suggestion like this on SO.
To clarify the difference between autocomplete and suggestion:
autocomplete: foo [foobar, foobaz]
suggestion: foo [barfoo, foobar, foobaz], or even better, with 'did you mean' feature: [barfoo, foobar, foobaz, fobar, fobaz]
I suppose I need some full text search in tags (all letters indexed, not just words). There would be no problem to do it witch regex or other patterns for limited number of tags (even client side).
But how to implement this feature for big number of tags?
Is there any particular reason (besides URL) the tags on SO are dash separated? What about Unicode characters in tags?
I store the tags in the table with the following columns: id, tagname.
My SQL query returns objects with following fields: id, tagname, count
(I use Doctrine ORM and pgsql as default db driver.)
I would go with SELECTING them from database by REGEXP at every keypress. I did this on my sites and the was no prefrormance problem (I do not have heavy loaded server thought). If you do not like this idea, I would cash all 1-5 letters combinations which will users enter and refresh them on daily basis in separate table. If this table is indexed than you have very fast implementation.
To elaborate more on the second appreach:
Briefly: 1. Make a table SEARCHTABLE representing 1-n relationship betwean keywords (limit it to 3-4 letters) and primary IDs of tags. 2. INDEX on both fields. 3. Everytime the user makes a search do look at the SEARCHTABLE and if the combination is there, use that - very fast, as everything is indexed. If not do the regexp search and put all results to SEARCHTABLE.
Notes:
You should invalidate the table if
you add tags, but this should much
less often than a search. When
invalidating table you do not
necesarilly TRUNCATE it, you can
easily rebuild it taking all
keywords into account.
If you want to speed it up, you can "pregenerate" all two or even three
letters searches.
If you care enough, you should be using information from n-1 letter kewords to generate
the n letter keyword. It speeds the things tremendously. Imagine that user has typed "mo"
and you have shown them appropriate result from SEARCHTABLE. Than when she types "n"
giving it "mon" you need only serach trough already selected items to generate new
response.
Hope it is more comprehensive now.
Related
I have a table named buildings
each building has zero - n images
I have two solutions
the first one (the classic solution) using two tables:
buildings(id, name, address)
building_images(id, building_id, image_url)
and the second solution using olny one table
buildings(id, name, address, image_urls_csv)
Given I won't need to search by image URL obviously,
I think the second solution (using image_urls_csv column) is easier to use, and no need to create another table just to keep the images, also I will avoid the hassle of multiple queries or joining.
the question is, if I don't really want to filter, search or group by the filed value, can I just make it CSV?
On the one hand, by simply having a column of image_urls_list avoids joins or multiple queries, yes. A single round-trip to the db is always a plus.
On the other hand, you then have a string of urls that you need to parse. What happens when a URL has a comma in it? Oh, I know, you quote it. But now you need a parser that is beyond a simple naive split on commas. And then, three months from now, someone will ask you which buildings share a given image, and you'll go through contortions to handle quotes, not-quotes, and entries that are at the beginning or end of the string (and thus don't have commas on either side). You'll start writing some SQL to handle all this and then say to heck with it all and push it up to your higher-level language to parse each entry and tell if a given image is in there, and find that this is slow, although you'll realise that you can at least look for %<url>% to limit it, ... and now you've spent more time trying to hack around your performance improvement of putting everything into a single entry than you saved by avoiding joins.
A year later, someone will give you a building with so many URLs that it overflows the text limit you put in for that field, breaking the whole thing. Or add some extra fields to each for extra metadata ("last updated", "expires", ...).
So, yes, you absolutely can put in a list of URLs here. And if this is postgres or any other db that has arrays as a first-class field type, that may be okay. But do yourself a favour, and keep them separate. It's a moderate amount of up-front pain, and the long-term gain is probably going to make you very happy you did.
Not
"Given I won't need to search by image URL obviously" is an assumption that you cannot make about a database. Even if you never do end up searching by url, you might add other attributes of building images, such as titles, alt tags, width, height, etc, so you would end up having to serialize all this data in that one column, and then you would not be able to index any of it. Plus, if you serialize it with one language, then you or whoever comes after you using a different language will either have to install some 3rd party library to deserialize your stuff or write their own deserialization function.
The only case that I can think of where you should keep serialized data in a database is when you inherit old software that you don't have time to fix yet.
I'm searching against a table of news articles. The 2 relevant columns are ArticleTitle and ArticleText. When I want to search an article for a particular term, i started out with
column LIKE '%term%'.
However that gave me a lot of articles with the term inside anchor links, for example <a href="example.com/*term*> which would potentially return an irrelevant article.
So then I switched to
column LIKE '% term %'.
The problem with this query is it didn't find articles who's title or text began/ended with the term. Also it didn't match against things like term- or term's, which I do want.
It seems like the query i want should be able to do something like this
'%[^a-z]term[^a-z]%
This should exclude terms within anchor links, but everything else. I think this query still excludes strings that begin/end with the term. Is there a better solution? Does SQL-Server's FULL TEXT INDEXING solve this problem?
Additionally, would it be a good idea to store ArticleTitle and ArticleText as HTML-free columns? Then i could use '%term%' without getting anchor links. These would be 2 extra columns though, because eventually i will need the original HTML for formatting purposes.
Thanks.
SQL Server's LIKE allows you to define Regex-like patterns like you described.
A better option is to use fulltext search:
WHERE CONTAINS(ArticleTitle, 'term')
exploits the index properly (the LIKE '%term%' query is slow), and provides other benefit in the search algorithm.
Additionally, you might benefit from storing a plaintext version of the article alongside the HTML version, and run your search queries on it.
SQL is not designed to interpret HTML strings. As such, you'd only be able to postpone the problem till a more difficult issue arrives (for example, a comment node that contains your search terms as part of a plain sentence).
You can still utilize FULL TEXT as a prefilter and then run an HTML analysis on the application layer to further filter your result set.
I'm using Lucene 4.10.3 with Java 1.7
I'm wondering whether it's possible to order query results the matching term?
Simply put, if my documents conatin a text field;
The query is
text:a*
I want documents with ab, then ac, then ad etc.
The real case is more complex however, what I'm actually trying to accomplish is to "stuff" a relational DB into my lucene Index (probably not the best idea?).
An appropriate example would be :
I have documents representing books in a library. every book has a title and also a list of people who has borrowed this book and the date of borrowing.
when a user searches for a book with title containing "JAVA", I want to give priority to books that were borrowed by this user. This could be accomplished by adding a TextField "borrowers", adding a SHOULD clause on it and ordering by score)
also, if there are several books with "JAVA" that this user has borrowed before, I want to show the most recent borrowed ones first. so I thought to create a TextField "borrowers" that will look like
borrowers : "user1__20150505 user2__20150506" etc.
I will add a BooleanClause borrowers: user1* and order by matching term.
any other solution ideas will be welcome
I understand your real problem is more complex, but maybe this is helpful anyway.
You could first search for Tokens in the index that match your query, then for each matching token executing a query using this token specifically.
See https://lucene.apache.org/core/6_0_1/core/org/apache/lucene/index/TermsEnum.html for that. Just seek to the prefix and iterate until the prefix stops matching.
In general it is sometimes easy to just issue two queries. For example one within the corpus of books the user as borrowed before and another witin the whole corpus.
These approaches may not work, but in that case you could implement a custom Scorer somehow mapping the ordering to a number.
See http://opensourceconnections.com/blog/2014/03/12/using-customscorequery-for-custom-solrlucene-scoring/
I'm creating a self-help FAQ type application and one of the requirements is that the end user has to be able to search for FAQ topics. I have three models of note, listed below with their relevant (i.e. searchable) columns:
Topic: Name, Description
Question: Name, Answer
Problem: Name, Solution
All three tables are linked to Topic via a TopicID column. The idea is to provide a single textbox where the user can enter a search query, something either as a sentence (e.g. "How do I perform X") or a phrase (e.g. "Performing X" or "Perform X"), and provide all Topics/Questions/Problems that have any of the words they entered in either the name or description/answer/solution fields; the model will only ever have those columns searchable and I don't have to worry about filtering out the common words like "How" and such (It would be nice but isn't a requirement as it's not an exact match but a fuzzy match).
For reasons outside of my control, I have to use a Stored Procedure. My question is what would be the most appropriate way to handle a search like this; I've seen similar questions regarding multiple columns but really there is not a variable number of columns, there are always two columns per table that are actually searchable. The issue is that the search query could, in theory, be nearly anything - a sentence, a phrase, a comma-separated list of terms (e.g. "x,y,z"), so I would have to split the search term into components (e.g. split on whitespace) and then search each pair of columns for every term? Is that reasonably easy to do in SQL Server? The alternative, a little messier, is to just pull all the data back and then split the query and filter the results in the server-side code as there shouldn't ever be that many items entered, but I would feel a little dirty doing something like that ;-)
Suggest creating a new Full Text Catalog, and assign the table and columns to that catalog. Ensure your catalog is being updated at the right frequency for your needs.
You can then query this catalog using the FREETEXT predicate. It sounds like you need to match on those suffixes like 'ing', so suggest FREETEXT over CONTAINS in this case.
You can use a variable in this search, so it'll be easy to fit into a stored proc.
declare #token varchar(256);
select #token = 'perform';
select * from Problem
where freetext(Name, #token)
or freetext(Solution, #token);
--this will match 'perform' and 'performing'
I'm looking for a pattern for performing a dynamic search on multiple tables.
I have no control over the legacy (and poorly designed) database table structure.
Consider a scenario similar to a resume search where a user may want to perform a search against any of the data in the resume and get back a list of resumes that match their search criteria. Any field can be searched at anytime and in combination with one or more other fields.
The actual sql query gets created dynamically depending on which fields are searched. Most solutions I've found involve complicated if blocks, but I can't help but think there must be a more elegant solution since this must be a solved problem by now.
Yeah, so I've started down the path of dynamically building the sql in code. Seems godawful. If I really try to support the requested ability to query any combination of any field in any table this is going to be one MASSIVE set of if statements. shiver
I believe I read that COALESCE only works if your data does not contain NULLs. Is that correct? If so, no go, since I have NULL values all over the place.
As far as I understand (and I'm also someone who has written against a horrible legacy database), there is no such thing as dynamic WHERE clauses. It has NOT been solved.
Personally, I prefer to generate my dynamic searches in code. Makes testing convenient. Note, when you create your sql queries in code, don't concatenate in user input. Use your #variables!
The only alternative is to use the COALESCE operator. Let's say you have the following table:
Users
-----------
Name nvarchar(20)
Nickname nvarchar(10)
and you want to search optionally for name or nickname. The following query will do this:
SELECT Name, Nickname
FROM Users
WHERE
Name = COALESCE(#name, Name) AND
Nickname = COALESCE(#nick, Nickname)
If you don't want to search for something, just pass in a null. For example, passing in "brian" for #name and null for #nick results in the following query being evaluated:
SELECT Name, Nickname
FROM Users
WHERE
Name = 'brian' AND
Nickname = Nickname
The coalesce operator turns the null into an identity evaluation, which is always true and doesn't affect the where clause.
Search and normalization can be at odds with each other. So probably first thing would be to get some kind of "view" that shows all the fields that can be searched as a single row with a single key getting you the resume. then you can throw something like Lucene in front of that to give you a full text index of those rows, the way that works is, you ask it for "x" in this view and it returns to you the key. Its a great solution and come recommended by joel himself on the podcast within the first 2 months IIRC.
What you need is something like SphinxSearch (for MySQL) or Apache Lucene.
As you said in your example lets imagine a Resume that will composed of several fields:
List item
Name,
Adreess,
Education (this could be a table on its own) or
Work experience (this could grow to its own table where each row represents a previous job)
So searching for a word in all those fields with WHERE rapidly becomes a very long query with several JOINS.
Instead you could change your framework of reference and think of the Whole resume as what it is a Single Document and you just want to search said document.
This is where tools like Sphinx Search do. They create a FULL TEXT index of your 'document' and then you can query sphinx and it will give you back where in the Database that record was found.
Really good search results.
Don't worry about this tools not being part of your RDBMS it will save you a lot of headaches to use the appropriate model "Documents" vs the incorrect one "TABLES" for this application.