I've built a full-text catalog on a SQL 2005 box that, after it's re-build process completes, runs extremely slow. I've implemented a hack (i.e. try...catch{do again}) so that my users don't get a timeout error; this makes me feel bad inside. All subsequent queries are lightning fast.
Has anyone experienced this issue and was/is there a solution? Thanks!
P.S. Yes, I've Google'd it many times. Even with my left hand.
It could also be caused by this Sql Server 'feature' which we've experienced.
You may experience a 45-second delay when you run a full-text query in an instance of SQL Server 2005 that is running on a server without Internet access
http://support.microsoft.com/default.aspx/kb/915850
this might not be a direct answer to your question, but the full-text-search on mssql was covered on stackoverflow podcast series, and the conclusion was it's not the best thing :)
so, if you are able to change it to a 3rd party library, you may try what's used by jeff & co., the Apache Lucene library. Java version available at http://lucene.apache.org/java/docs/ , and .net port at http://incubator.apache.org/lucene.net/
i've had this as well. first hit very slow and rest are fast. tried all sorts and couldnt resolve it.
would love to know the answer to this one.
You could prevent having to fully rebuild the index by "setting start background updateindex" and "start change tracking" (there should be an underscore between each word) on each table that is full text indexed.
This allows sql server to update the index only with changes when required. It may help your issue since the index is not being rebuilt.
I second the Lucene.Net suggestion. I have previously tried to build a 'search engine' of sorts using Full Text Search and SQL. It was always problematic when the search criteria gets complicated and often queries would time out. On my new site I built the search engine with Lucene.Net project and it works really well and is much faster than SQL FTS.
Related
I may need some assistance for my installation of FTS on my computer.
I have the requirement of practicing some stuff concerning FTS.
And at the beginning, I used SELECT SERVERPROPERTY('IsFullTextInstalled'); to check if FTS was installed on my desktop and the result was 0.
Then I started to find the solution by asking Professor Goo (Google), yet I still haven't found a solution that can resolve my problem after seeing some articles for approximately one hour.
And the followings are some information
Any suggestion, please.
I've found the answer and I'll answer to myself though it may be kind of idiotic for asking this. Well, what I had in my hand is 'ENU\x64\SQLEXPRWT_x64_ENU.exe' and, a person should download Express with Advanced Services(ENU\x64\SQLEXPRADV_x64_ENU.exe) and thne add the feature, like FTS, to the existing instance or the new one. In the end, the person can start to explore the functions provided by FTS.
I'm using MySQL & ColdFusion. Currently for searching TEXT fields I'm using LIKE in the database. Luckily my database is empty but soon the table will fill up and I fear I the LIKE SQL query will kill my app.
I'm looking for a solution that works with both MySQL & ColdFusion that will allow me to scalably offer search capabilities with my MySQL & ColdFusion app.
Thanks
Consider using ColdFusion's built in Verity search engine or Solr Search engine in ColdFusion 9, which is Apache Lucene. Good Luck!
Update: Coldfusion 9.0.1 has addressed several quirks in the Solr (apache lucene) search engine. Use it..!
You are right to worry about the LIKE operator's performance having scalability problems. But keep two things in mind.
First: column LIKE 'pattern%' works well if your column is indexed. It's column LIKE '%pattern%' that can cause real performance problems.
Second, mySQL has a good full-text search system built into it. See http://dev.mysql.com/doc/refman/5.1/en/fulltext-search.html
Whats makes you think that it will be a problem? Have you done any load testing? What is the worst case scenario max size of the table? Have you filled it to that level and tried it? Finally, do you actually need it to be "text"? MySQL has some very large varchars, would that do instead?
My point being, it sounds like you already have the simplest solution that might possibly work. Maybe you should prove that it does not work before over-engineering something else?
Lastly, to actually answer your question, you could cache the database into a verity search index and then search that (CF 9 offers another index engine as well). But your going to loose it being a live search.
I don't know if it is an option for your app but what I usually do is reserve like '%pattern%' for advanced searches defined by the user when a performance hit could be expected. When possible I default the search options selected by the user to 'Starts With.' I've searched '%pattern%' in a MySql 5 DB with 1.25 Million records on a low traffic site. The database doesn't seem to be the bottle neck, even on a field that isn't indexed. The customer wants all the records shown on the screen. Showing 10,000+ records seems to be the problem (lol). The DB may be less of a problem than you think depending on traffic.
We have an email service that hosts close to 10000 domains such that we store the headers of messages in a SQL Server database.
I need to implement an application that will search the message body for keywords. The messages are stored as files on a NAS storage system.
As a proof of concept, I had implemented a SQL server based search system were I would parse the message and store all the words in a database table along with the memberid and the messageid. The database was on a separate server to the headers database.
The problem with that system was that I ended up with a table with 600 million rows after processing messages on just one domain. Obviously this is not a very scalable solution.
Since the headers are stored in a SQL Server table, I am going to need to join the messageIDs from the search application to the header table to display the messages that contain the searched for keywords.
Any suggestions on a better architecture? Any better alternative to using SQL server? We receive over 20 million messages a day.
We are a small company with limited resources with respect to servers, maintenance etc.
Thanks
have a look at Hadoop. It's complete "map-reduce" framework for working with huge datasets inspired by Google. It think (but I could be wrong) Rackspace is using it for email search for their clients.
lucene.net will help you a lot, but no matter how you approach this, it's going to be a lot of work.
Consider not using SQL for this. It isn't helping.
GREP and other flat-file techniques for searching the text of the headers is MUCH faster and much simpler.
You can also check out the java lucene stuff which might be useful to you. Both Katta which is a distributed lucene index and Solr which can use rsync for index syncing might be useful. While I don't consider either to be very elegant it is often better to use something that is already built and known to work before embarking on actual development. Without knowing more details its hard to make a more specific recommendation.
If you can break up your 600 million rows, look into database sharding. Any query across all rows is going to be slow. At very least you could break up by language. If they're all English, well, find some way to split the data that makes sense based on common searches. I'm just guessing here but maybe domains could be grouped by TLD (.com, .net, .org, etc).
For fulltext search, compare SQL Server vs Lucene.NET vs cLucene vs MySQL vs PostgreSQL. Note full-text search will be faster if you don't need to rank the results. If a database is still slow look into performance tuning and if that fails look into a Linux-based db.
http://incubator.apache.org/lucene.net/
http://sourceforge.net/projects/clucene/
i wonder if BigTable (http://en.wikipedia.org/wiki/BigTable) does searching.
Look into the SQL Server full text search services/functionality. I haven't used it myself, but I once read that Stack Overflow uses it.
three solutions:
Use an already-existant text search engine (lucene is the most mentioned, there are several more)
Store the whole message in the SQL database, and use included full text search (most DBs have it these days).
Don't create a new record for each word occurrence, just add a new value to a big field in the word record. Even better if you don't use SQL for this table, use a key-value store where the key is the word and the value is the list of occurrences. Check some Inverted Index bibliography for inspiration
but to be honest, i think the only reasonable approach is #1
I'm trying to implement a search feature for an offline-accessible StackOverflow, and I'm noticing some problems with using MySQLs FULLTEXT indexing.
Specifically, by default FULLTEXT indexing is restricted to words between 4 and 84 characters long. Terms such as "PHP" or "SQL" would not meet the minimum length and searching for those terms would yield no results.
It is possible to modify the variable which controls the minimum length a word needs to be to be indexed (ft_min_word_len), but this is a system-wide change requiring indexes in all databases to be rebuilt. On the off chance others find this app useful, I'd rather keep these sort of variables as vanilla as possible. I found a post on this site the other day stating that changing that value is just a bad idea anyway.
Another issue is with terms like "VB.NET" where, as far as I can tell, the period in the middle of the term separates it into two indexed values - VB and NET. Again, this means searches for "VB.NET" would return nothing.
Finally, since I'm doing a direct dump of the monthly XML-based dumps, all values are converted to HTML Entities and I'm concerned that this might have an impact on my search results.
I found a blog post which tries to address these issues with the following advice:
keep two copies of your data - one with markup, etc. for display, and one modified for searching (remove unwanted words, markup, etc)
pad short terms so they will be indexed, I assume with a pre/suffix.
What I'd like to know is, are these really the best workarounds for these issues? It seems like semi-duplicating a > 1GB table is wasteful, but maybe that's just me.
Also, if anyone could recommend a good site to understand MySQL's FULLTEXT indexing, I'd appreciate it. To keep this question from being too cluttered, please leave the site recommendations in the question comments, or email me directly at the site on my user profile).
Thanks!
Additional Info:
I think I should clarify a couple of things.
I know "MySQL" tends to lead to the assumption of "web application", but that's not what I'm going for here. I could install Apache and PHP and run things that way, but I'm trying to keep this light. I can use my website for playing with PHP, so I don't feel the need to install it on my home machine too. I also hope this could be useful for others as well, and I don't want to force anyone else into installing a bunch of extra utilities. I went with MySQL since it was easy and needing to install some sort of DB was unavoidable.
The specifics of the project were going to be:
Desktop application written in C# (WinForms)
MySQL backend
I'm starting to wonder if I should just say to hell with it, and install everything I'd need to make this an (offline) webapp. As much as we'd all like to think our pet project is going to be used and loved by the community at large, I should know by now that this is likely going end up being only used by a single user.
From what was already said, I understand, that MySQL FullText is not for you ;) But why stick to MySQL? Try Sphinx:
http://www.sphinxsearch.com/
It will solve most of your problems.
I'm setting up a web application with a FreeBSD PostgreSQL back-end. I'm looking for some database performance optimization tool/technique.
Database optimization is usually a combination of two things
Reduce the number of queries to the database
Reduce the amount of data that needs to be looked at to answer queries
Reducing the amount of queries is usually done by caching non-volatile/less important data (e.g. "Which users are online" or "What are the latest posts by this user?") inside the application (if possible) or in an external - more efficient - datastore (memcached, redis, etc.). If you've got information which is very write-heavy (e.g. hit-counters) and doesn't need ACID-semantics you can also think about moving it out of the Postgres database to more efficient data stores.
Optimizing the query runtime is more tricky - this can amount to creating special indexes (or indexes in the first place), changing (possibly denormalizing) the data model or changing the fundamental approach the application takes when it comes to working with the database. See for example the Pagination done the Postgres way talk by Markus Winand on how to rethink the concept of pagination to make it more database efficient
Measuring queries the slow way
But to understand which queries should be looked at first you need to know how often they are executed and how long they run on average.
One approach to this is logging all (or "slow") queries including their runtime and then parsing the query log. A good tool for this is pgfouine which has already been mentioned earlier in this discussion, it has since been replaced by pgbadger which is written in a more friendly language, is much faster and more actively maintained.
Both pgfouine and pgbadger suffer from the fact that they need query-logging enabled, which can cause a noticeable performance hit on the database or bring you into disk space troubles on top of the fact that parsing the log with the tool can take quite some time and won't give you up-to-date insights on what is going in the database.
Speeding it up with extensions
To address these shortcomings there are now two extensions which track query performance directly in the database - pg_stat_statements (which is only helpful in version 9.2 or newer) and pg_stat_plans. Both extensions offer the same basic functionality - tracking how often a given "normalized query" (Query string minus all expression literals) has been run and how long it took in total. Due to the fact that this is done while the query is actually run this is done in a very efficient manner, the measurable overhead was less than 5% in synthetic benchmarks.
Making sense of the data
The list of queries itself is very "dry" from an information perspective. There's been work on a third extension trying to address this fact and offer nicer representation of the data called pg_statsinfo (along with pg_stats_reporter), but it's a bit of an undertaking to get it up and running.
To offer a more convenient solution to this problem I started working on a commercial project which is focussed around pg_stat_statements and pg_stat_plans and augments the information collected by lots of other data pulled out of the database. It's called pganalyze and you can find it at https://pganalyze.com/.
To offer a concise overview of interesting tools and projects in the Postgres Monitoring area i also started compiling a list at the Postgres Wiki which is updated regularly.
pgfouine works fairly well for me. And it looks like there's a FreeBSD port for it.
I've used pgtop a little. It is quite crude, but at least I can see which query is running for each process ID.
I tried pgfouine, but if I remember, it's an offline tool.
I also tail the psql.log file and set the logging criteria down to a level where I can see the problem queries.
#log_min_duration_statement = -1 # -1 is disabled, 0 logs all statements
# and their durations, > 0 logs only
# statements running at least this time.
I also use EMS Postgres Manager to do general admin work. It doesn't do anything for you, but it does make most tasks easier and makes reviewing and setting up your schema more simple. I find that when using a GUI, it is much easier for me to spot inconsistencies (like a missing index, field criteria, etc.). It's only one of two programs I'm willing to use VMWare on my Mac to use.
Munin is quite simple yet effective to get trends of how the database is evolving and performing over time. In the standard kit of Munin you can among other thing monitor the size of the database, number of locks, number of connections, sequential scans, size of transaction log and long running queries.
Easy to setup and to get started with and if needed you can write your own plugin quite easily.
Check out the latest postgresql plugins that are shipped with Munin here:
http://munin-monitoring.org/browser/branches/1.4-stable/plugins/node.d/
Well, the first thing to do is try all your queries from psql using "explain" and see if there are sequential scans that can be converted to index scans by adding indexes or rewriting the query.
Other than that, I'm as interested in the answers to this question as you are.
Check out Lightning Admin, it has a GUI for capturing log statements, not perfect but works great for most needs. http://www.amsoftwaredesign.com
DBTuna http://www.dbtuna.com/postgresql_monitor.php has recently started supporting PostgreSQL monitoring. We use it extensively for MySQL monitoring, so if it provides the same for Postgres then it should be a good fit for you too.