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  • NLP - Queries using semantic wildcards in full text searching, maybe with Lucene?

    - by Zsolt
    Let's say I have a big corpus (for example in english or an arbitrary language), and I want to perform some semantic search on it. For example I have the query: "Be careful: [art] armada of [sg] is coming to [do sg]!" And the corpus contains the following sentence: "Be careful: an armada of alien ships is coming to destroy our planet!" It can be seen that my query string could contain "semantic placeholders", such as: [art] - some placeholder for articles (for example a / an in English) [sg], [do sg] - some placeholders for NPs and VPs (subjects and predicates) I would like to develop a library which would be capable to handle these queries efficiently. I suspect that some kind of POS-tagging would be necessary for parsing the text, but because I don't want to fully reimplement an already existing full-text search engine to make it work, I'm considering that how could I integrate this behaviour into a search engine like Lucene? I know there are SpanQueries which could behave similarly in some cases, but as I can see, Lucene doesn't do any semantic stuff with stored texts. It is possible to implement a behavior like this? Or do I have to write an own search engine?

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  • How backup and restore Horde manualy

    - by Thomas
    how can I backup and restore my horde sql database The Databse ist located in /var/lib/mysql/horde There are many *.frm files and one db.opt My Server ist broken, so I want to reinstall it. Can i copy this files to a USB Stick, then restore the entire server without horde and then simply copy the files in the same directory? Or habe I do something like "mysqldump" to delete an reinztall the database? Thank you, Thomas

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  • SQL SERVER – Contest – Summary of 5 Day and Additional Information

    - by pinaldave
      I am overwhelmed with the response of our contest ran earlier this week. Every day we are giving away USD 198 worth give aways to readers in USA and India. If you have not participated so far, I encourage you to participate today itself. Here are links to our 5 day contest. The winner of the contest will be announced on August 20th. Query Hint – Contest Win Joes 2 Pros Combo (USD 198) – Day 1 of 5 Identity Fields – Contest Win Joes 2 Pros Combo (USD 198) – Day 2 of 5 Clustered Index and Primary Key – Contest Win Joes 2 Pros Combo (USD 198) – Day 3 of 5 Expanding Views – Contest Win Joes 2 Pros Combo (USD 198) – Day 4 of 5 Understanding XML – Contest Win Joes 2 Pros Combo (USD 198) – Day 5 of 5 Here are a few important notes related to the contest. A few people asked me what should they do as they have forgotten to mention their country in the response. Please resubmit with correct data, we will only consider latest entry from one person. What if you are not from the USA or India? Participate in the Bonus Quiz. Leave a comment for each of the questions above with your favorite article and you may be eligible for winning something cool. What if I am winner of two contests out of 5 contests? Well, in that case, we will send you one set of Combo Kit and Amazon Gift Card of USD 100 for another contest which you won. Can I exchange my kit with other stuff? No, if you do not want kit, give it to someone who needs it. Btw, I strongly suggest that you participate in the Bonus Quiz. There is something cool for everyone! Reference: Pinal Dave (http://blog.sqlauthority.com)         Filed under: Database, DBA, Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQLAuthority News – Scaling Up Your Data Warehouse with SQL Server 2008 R2

    - by pinaldave
    Data Warehouses are suppose to be containing huge amount of the data from the beginning. However, there are cases when too big is not enough. Every Data Warehouse Admin will agree that they have faced situation where they will need to scale up their data warehouse. Microsoft has released white paper discussing the same. Here is the abstract from the Microsoft Official site: SQL Server 2008 introduced many new functional and performance improvements for data warehousing, and SQL Server 2008 R2 includes all these and more. This paper discusses how to use SQL Server 2008 R2 to get great performance as your data warehouse scales up. We present lessons learned during extensive internal data warehouse testing on a 64-core HP Integrity Superdome during the development of the SQL Server 2008 release, and via production experience with large-scale SQL Server customers. Our testing indicates that many customers can expect their performance to nearly double on the same hardware they are currently using, merely by upgrading to SQL Server 2008 R2 from SQL Server 2005 or earlier, and compressing their fact tables. We cover techniques to improve manageability and performance at high-scale, encompassing data loading (extract, transform, load), query processing, partitioning, index maintenance, indexed view (aggregate) management, and backup and restore. Scaling Up Your Data Warehouse with SQL Server 2008 R2 Reference: Pinal Dave (http://blog.SQLAuthority.com)   Filed under: PostADay, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – A Cool Trick – Restoring the Default SQL Server Management Studio – SSMS

    - by pinaldave
    “I do not know where my windows went!” “I just closed my object explorer and now I cannot find it.” “How do I get my original windows layout back in SQL Server Management Studio?” “How do I get the window which was there in left side back again?” Since last 2-3 years, every single day I receive more than 5 emails on SSMS and its layout. For the beginners it is very common to get confused when they attempt to change SQL Server Management Studio’s windows layout. They often change the layout and are not able to get the original layout back. Often people do not change the layout whole of their life, leading to uncomfortable feeling when they go to another’s computer where the windows are differently placed. Today’s blog post is dedicated all the beginners in SQL Server. It is extremely simple to reset the SSMS layout to default layout. The default layout involves 2 major things 1) Object Explorer on left side 2) Query Windows on right side (80% screen estate). Personally I am so used to this as well that if there is any other changes in the same, I do not enjoy working on the environment. Well, the solution to rest the SSMS layout is very simple. One can do it in split seconds.  To restore the default configuration, on the Window menu, click Reset Window Layout. Have you ever used this feature? Do you feel uncomfortable when SSMS layout is not in default state? How do you address this situation? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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  • SQLAuthority News – Whitepaper Download – Using Star Join and Few-Outer-Row Optimizations to Improve Data Warehousing Queries

    - by pinaldave
    Size of the database is growing every day. Many organizations now a days have more than TB of the Data in their system. Performance is always part of the issue. Microsoft is really paying attention to the same and also focusing on improving performance for Data Warehousing. Microsoft has recently released whitepaper on the performance tuning subject of Data Warehousing. Here is the abstract about the whitepaper from official site: In this white paper we discuss two of the new features introduced in SQL Server 2008, Star Join and Few-Outer-Row optimizations. These two features are in SQL Server 2008 R2 as well.  We test the performance of SQL Server 2008 on a set of complex data warehouse queries designed to highlight the effect of these two features and observed a significant performance gain over SQL Server 2005 (without these two features). The results observed also apply to SQL Server 2008 R2.  On average, about 75 percent of the query execution time has been reduced, compared to SQL Server 2005. We also include data that shows a reduction in the number of rows processed and improved balance in parallel queries, both of which highlight the important role the Star Join and Few Outer-Row features played. I encouraged all of those interested in Data Warehouse to read it and see if they can learn the tricks. Using Star Join and Few-Outer-Row Optimizations to Improve Data Warehousing Queries Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology

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  • SQL SERVER – Load Generator – Free Tool From CodePlex

    - by pinaldave
    One of the most common questions I receive is if there any tool available to generate load on SQL Server. Absolutely there is a fabulous free tool available to generate load on SQL Server on Codeplex. This tool was released in 2008 but it is still extremely relevant to generate the load on SQL Server as well works fabulously. CodePlex is a project initiated by Microsoft for hosting open source softwares. The best part of this SQL Server Load Generator is that users can run multiple simultaneous queries again SQL Server using different login account and different application name. The interface of the tool is extremely easy to use and very intuitive as well. One of the things which I felt needed improvement was a default configuration. As every single time when I was adding a query the default settings were showing up and I had to manually change that. However, when I went to Menu >> Tools >>Options I was really happy as it has options to change every single default which is available. Here one can give default username, password, database name as well various settings related to configuration. Additionally application logging is also possible through the options. A couple of other important points I noticed was the button to reset counters as well status bar containing useful information of Total Threads, Completed Queries and Failed Queries. I use this frequently for my load testing. What tool do you use for SQL Server Load Generator? Download SQL Load Generator Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL, Technology

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  • SQL SERVER – Validating Unique Columnname Across Whole Database

    - by pinaldave
    I sometimes come across very strange requirements and often I do not receive a proper explanation of the same. Here is the one of those examples. Asker: “Our business requirement is when we add new column we want it unique across current database.” Pinal: “Why do you have such requirement?” Asker: “Do you know the solution?” Pinal: “Sure I can come up with the answer but it will help me to come up with an optimal answer if I know the business need.” Asker: “Thanks – what will be the answer in that case.” Pinal: “Honestly I am just curious about the reason why you need your column name to be unique across database.” (Silence) Pinal: “Alright – here is the answer – I guess you do not want to tell me reason.” Option 1: Check if Column Exists in Current Database IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn') BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END Option 2: Check if Column Exists in Current Database in Specific Table IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn' AND OBJECT_ID = OBJECT_ID(N'tableName')) BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END I guess user did not want to share the reason why he had a unique requirement of having column name unique across databases. Here is my question back to you – have you faced a similar situation ever where you needed unique column name across a database. If not, can you guess what could be the reason for this kind of requirement?  Additional Reference: SQL SERVER – Query to Find Column From All Tables of Database Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL System Table, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Weekly Series – Memory Lane – #007

    - by pinaldave
    Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2006 Find Stored Procedure Related to Table in Database – Search in All Stored Procedure In 2006 I wrote a small script which will help user  find all the Stored Procedures (SP) which are related to one or more specific tables. This was quite a popular script however, in SQL Server 2012 the same can be achieved using new DMV sys.sql-expression_dependencies. I recently blogged about it over Find Referenced or Referencing Object in SQL Server using sys.sql_expression_dependencies. 2007 SQL SERVER – Versions, CodeNames, Year of Release 1993 – SQL Server 4.21 for Windows NT 1995 – SQL Server 6.0, codenamed SQL95 1996 – SQL Server 6.5, codenamed Hydra 1999 – SQL Server 7.0, codenamed Sphinx 1999 – SQL Server 7.0 OLAP, codenamed Plato 2000 – SQL Server 2000 32-bit, codenamed Shiloh (version 8.0) 2003 – SQL Server 2000 64-bit, codenamed Liberty 2005 – SQL Server 2005, codenamed Yukon (version 9.0) 2008 – SQL Server 2008, codenamed Katmai (version 10.0) 2011 – SQL Server 2008, codenamed Denali (version 11.0) Search String in Stored Procedure Searching sting in the stored procedure is one of the most frequent task developer do. They might be searching for a table, view or any other details. I have written a script to do the same in SQL Server 2000 and SQL Server 2005. This is worth bookmarking blog post. There is an alternative way to do the same as well here is the example. 2008 SQL SERVER – Refresh Database Using T-SQL NO! Some of the questions have a single answer NO! You may want to read the question in the original blog post. I had a great time saying No! SQL SERVER – Delete Backup History – Cleanup Backup History SQL Server stores history of all the taken backup forever. History of all the backup is stored in the msdb database. Many times older history is no more required. Following Stored Procedure can be executed with a parameter which takes days of history to keep. In the following example 30 is passed to keep a history of month. 2009 Stored Procedure are Compiled on First Run – SP taking Longer to Run First Time Is stored procedure pre-compiled? Why the Stored Procedure takes a long time to run for the first time?  This is a very common questions often discussed by developers and DBAs. There is an absolutely definite answer but the question has been discussed forever. There is a misconception that stored procedures are pre-compiled. They are not pre-compiled, but compiled only during the first run. For every subsequent runs, it is for sure pre-compiled. Read the entire article for example and demonstration. Removing Key Lookup – Seek Predicate – Predicate – An Interesting Observation Related to Datatypes This is one of the most important performance tuning lesson on my blog. I suggest this weekend you spend time reading them and let me know what you think about the concepts which I have demonstrated in the four part series. Part 1 | Part 2 | Part 3 | Part 4 Seek Predicate is the operation that describes the b-tree portion of the Seek. Predicate is the operation that describes the additional filter using non-key columns. Based on the description, it is very clear that Seek Predicate is better than Predicate as it searches indexes whereas in Predicate, the search is on non-key columns – which implies that the search is on the data in page files itself. Policy Based Management – Create, Evaluate and Fix Policies This article will cover the most spectacular feature of SQL Server – Policy-based management and how the configuration of SQL Server with policy-based management architecture can make a powerful difference. Policy based management is loaded with several advantages. It can help you implement various policies for reliable configuration of the system. It also provides additional administration assistance to DBAs and helps them effortlessly manage various tasks of SQL Server across the enterprise. 2010 Recycle Error Log – Create New Log file without Server Restart Once I observed a DBA to restaring the SQL Server when he needed new error log file. This was funny and sad both at the same time. There is no need to restart the server to create a new log file or recycle the log file. You can run sp_cycle_errorlog and achieve the same result. Get Database Backup History for a Single Database Simple but effective script! Reducing CXPACKET Wait Stats for High Transactional Database The subject is very complex and I have done my best to simplify the concept. In simpler words, when a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. Threads which came first have to wait for the slower thread to finish. The Wait by a specific completed thread is called CXPACKET Wait Stat. Information Related to DATETIME and DATETIME2 There are quite a lot of confusion with DATETIME and DATETIME2. DATETIME2 is also one of the underutilized datatype of SQL Server.  In this blog post I have written a follow up of the my earlier datetime series where I clarify a few of the concepts related to datetime. Difference Between GETDATE and SYSDATETIME Difference Between DATETIME and DATETIME2 – WITH GETDATE Difference Between DATETIME and DATETIME2 2011 Introduction to CUME_DIST – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical function CUME_DIST(). This function provides cumulative distribution value. It will be very difficult to explain this in words so I will attempt small example to explain you this function. Instead of creating new table, I will be using AdventureWorks sample database as most of the developer uses that for experiment. Introduction to FIRST _VALUE and LAST_VALUE – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical functions FIRST_VALUE() and LAST_VALUE(). This function returns first and last value from the list. It will be very difficult to explain this in words so I’d like to attempt to explain its function through a brief example. Instead of creating a new table, I will be using the AdventureWorks sample database as most developers use that for experiment purposes. OVER clause with FIRST _VALUE and LAST_VALUE – Analytic Functions Introduced in SQL Server 2012 – ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING “Don’t you think there is bug in your first example where FIRST_VALUE is remain same but the LAST_VALUE is changing every line. I think the LAST_VALUE should be the highest value in the windows or set of result.” Puzzle – Functions FIRST_VALUE and LAST_VALUE with OVER clause and ORDER BY You can see that row number 2, 3, 4, and 5 has same SalesOrderID = 43667. The FIRST_VALUE is 78 and LAST_VALUE is 77. Now if these function was working on maximum and minimum value they should have given answer as 77 and 80 respectively instead of 78 and 77. Also the value of FIRST_VALUE is greater than LAST_VALUE 77. Why? Explain in detail. Introduction to LEAD and LAG – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical function LEAD() and LAG(). This functions accesses data from a subsequent row (for lead) and previous row (for lag) in the same result set without the use of a self-join . It will be very difficult to explain this in words so I will attempt small example to explain you this function. Instead of creating new table, I will be using AdventureWorks sample database as most of the developer uses that for experiment. A Real Story of Book Getting ‘Out of Stock’ to A 25% Discount Story Available Our book was out of stock in 48 hours of it was arrived in stock! We got call from the online store with a request for more copies within 12 hours. But we had printed only as many as we had sent them. There were no extra copies. We finally talked to the printer to get more copies. However, due to festivals and holidays the copies could not be shipped to the online retailer for two days. We knew for sure that they were going to be out of the book for 48 hours. This is the story of how we overcame that situation! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Storing 64-bit Unsigned Integer Value in Database

    - by Pinal Dave
    Here is a very interesting question I received in an email just another day. Some questions just are so good that it makes me wonder how come I have not faced it first hand. Anyway here is the question - “Pinal, I am migrating my database from MySQL to SQL Server and I have faced unique situation. I have been using Unsigned 64-bit integer in MySQL but when I try to migrate that column to SQL Server, I am facing an issue as there is no datatype which I find appropriate for my column. It is now too late to change the datatype and I need immediate solution. One chain of thought was to change the data type of the column from Unsigned 64-bit (BIGINT) to VARCHAR(n) but that will just change the data type for me such that I will face quite a lot of performance related issues in future. In SQL Server we also have the BIGINT data type but that is Signed 64-bit datatype. BIGINT datatype in SQL Server have range of -2^63 (-9,223,372,036,854,775,808) to 2^63-1 (9,223,372,036,854,775,807). However, my digit is much larger than this number. Is there anyway, I can store my big 64-bit Unsigned Integer without loosing much of the performance of by converting it to VARCHAR.” Very interesting question, for the sake of the argument, we can ask user that there should be no need of such a big number or if you are taking about identity column I really doubt that if your table will grow beyond this table. Here the real question which I found interesting was how to store 64-bit unsigned integer value in SQL Server without converting it to String data type. After thinking a bit, I found a fairly simple answer. I can use NUMERIC data type. I can use NUMERIC(20) datatype for 64-bit unsigned integer value, NUMERIC(10) datatype for 32-bit unsigned integer value and NUMERIC(5) datatype for 16-bit unsigned integer value. Numeric datatype supports 38 maximum of 38 precision. Now here is another thing to keep in mind. Using NUMERIC datatype will indeed accept the 64-bit unsigned integer but in future if you try to enter negative value, it will also allow the same. Hence, you will need to put any additional constraint over column to only accept positive integer there. Here is another big concern, SQL Server will store the number as numeric and will treat that as a positive integer for all the practical purpose. You will have to write in your application logic to interpret that as a 64-bit Unsigned Integer. On another side if you are using unsigned integers in your application, there are good chance that you already have logic taking care of the same. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Datatype

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  • SQLAuthority News – Microsoft Whitepaper – AlwaysOn Solution Guide: Offloading Read-Only Workloads to Secondary Replicas

    - by pinaldave
    SQL Server 2012 has many interesting features but the most talked feature is AlwaysOn. Performance tuning is always a hot topic. I see lots of need of the same and lots of business around it. However, many times when people talk about performance tuning they think of it as a either query tuning, performance tuning, or server tuning. All are valid points, but performance tuning expert usually understands the business workload and business logic before making suggestions. For example, if performance tuning expert analysis workload and realize that there are plenty of reports as well read only queries on the server they can for sure consider alternate options for the same. If read only data is not required real time or it can accept the data which is delayed a bit it makes sense to divide the workload. A secondary replica of the original data which can serve all the read only queries and report is a good idea in most of the cases where there is plenty of workload which is not dependent on the real time data. SQL Server 2012 has introduced the feature of AlwaysOn which can very well fit in this scenario and provide a solution in Read-Only Workloads. Microsoft has recently announced a white paper which is based on absolutely the same subject. I recommend it to read for every SQL Enthusiast who is are going to implement a solution to offload read-only workloads to secondary replicas. Download white paper AlwaysOn Solution Guide: Offloading Read-Only Workloads to Secondary Replicas Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: AlwaysOn

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  • InnoDB Compression Improvements in MySQL 5.6

    - by Inaam Rana
    MySQL 5.6 comes with significant improvements for the compression support inside InnoDB. The enhancements that we'll talk about in this piece are also a good example of community contributions. The work on these was conceived, implemented and contributed by the engineers at Facebook. Before we plunge into the details let us familiarize ourselves with some of the key concepts surrounding InnoDB compression. In InnoDB compressed pages are fixed size. Supported sizes are 1, 2, 4, 8 and 16K. The compressed page size is specified at table creation time. InnoDB uses zlib for compression. InnoDB buffer pool will attempt to cache compressed pages like normal pages. However, whenever a page is actively used by a transaction, we'll always have the uncompressed version of the page as well i.e.: we can have a page in the buffer pool in compressed only form or in a state where we have both the compressed page and uncompressed version but we'll never have a page in uncompressed only form. On-disk we'll always only have the compressed page. When both compressed and uncompressed images are present in the buffer pool they are always kept in sync i.e.: changes are applied to both atomically. Recompression happens when changes are made to the compressed data. In order to minimize recompressions InnoDB maintains a modification log within a compressed page. This is the extra space available in the page after compression and it is used to log modifications to the compressed data thus avoiding recompressions. DELETE (and ROLLBACK of DELETE) and purge can be performed without recompressing the page. This is because the delete-mark bit and the system fields DB_TRX_ID and DB_ROLL_PTR are stored in uncompressed format on the compressed page. A record can be purged by shuffling entries in the compressed page directory. This can also be useful for updates of indexed columns, because UPDATE of a key is mapped to INSERT+DELETE+purge. A compression failure happens when we attempt to recompress a page and it does not fit in the fixed size. In such case, we first try to reorganize the page and attempt to recompress and if that fails as well then we split the page into two and recompress both pages. Now lets talk about the three major improvements that we made in MySQL 5.6.Logging of Compressed Page Images:InnoDB used to log entire compressed data on the page to the redo logs when recompression happens. This was an extra safety measure to guard against the rare case where an attempt is made to do recovery using a different zlib version from the one that was used before the crash. Because recovery is a page level operation in InnoDB we have to be sure that all recompress attempts must succeed without causing a btree page split. However, writing entire compressed data images to the redo log files not only makes the operation heavy duty but can also adversely affect flushing activity. This happens because redo space is used in a circular fashion and when we generate much more than normal redo we fill up the space much more quickly and in order to reuse the redo space we have to flush the corresponding dirty pages from the buffer pool.Starting with MySQL 5.6 a new global configuration parameter innodb_log_compressed_pages. The default value is true which is same as the current behavior. If you are sure that you are not going to attempt to recover from a crash using a different version of zlib then you should set this parameter to false. This is a dynamic parameter.Compression Level:You can now set the compression level that zlib should choose to compress the data. The global parameter is innodb_compression_level - the default value is 6 (the zlib default) and allowed values are 1 to 9. Again the parameter is dynamic i.e.: you can change it on the fly.Dynamic Padding to Reduce Compression Failures:Compression failures are expensive in terms of CPU. We go through the hoops of recompress, failure, reorganize, recompress, failure and finally page split. At the same time, how often we encounter compression failure depends largely on the compressibility of the data. In MySQL 5.6, courtesy of Facebook engineers, we have an adaptive algorithm based on per-index statistics that we gather about compression operations. The idea is that if a certain index/table is experiencing too many compression failures then we should try to pack the 16K uncompressed version of the page less densely i.e.: we let some space in the 16K page go unused in an attempt that the recompression won't end up in a failure. In other words, we dynamically keep adding 'pad' to the 16K page till we get compression failures within an agreeable range. It works the other way as well, that is we'll keep removing the pad if failure rate is fairly low. To tune the padding effort two configuration variables are exposed. innodb_compression_failure_threshold_pct: default 5, range 0 - 100,dynamic, implies the percentage of compress ops to fail before we start using to padding. Value 0 has a special meaning of disabling the padding. innodb_compression_pad_pct_max: default 50, range 0 - 75, dynamic, the  maximum percentage of uncompressed data page that can be reserved as pad.

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  • SQL SERVER – A Puzzle Part 2 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value

    - by pinaldave
    Before continuing this blog post – please read the first part of the SEQUENCE Puzzle here A Puzzle – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value. Where we played a simple guessing game about predicting next value. The answers the of puzzle is shared on the blog posts as a comment. Now here is the next puzzle based on yesterday’s puzzle. First execute the script which I have written here. The only difference between yesterday’s script is that I have removed the MINVALUE as 1 from the syntax. Now guess what will be the next value as requested in the query. USE TempDB GO -- Create sequence CREATE SEQUENCE dbo.SequenceID AS BIGINT START WITH 3 INCREMENT BY 1 MAXVALUE 5 CYCLE NO CACHE; GO -- Following will return 3 SELECT next value FOR dbo.SequenceID; -- Following will return 4 SELECT next value FOR dbo.SequenceID; -- Following will return 5 SELECT next value FOR dbo.SequenceID; -- Following will return which number SELECT next value FOR dbo.SequenceID; -- Clean up DROP SEQUENCE dbo.SequenceID; GO Above script gave me following resultset. 3 is the starting value and 5 is the maximum value. Once Sequence reaches to maximum value what happens? and WHY? I (kindly) suggest you try to attempt to answer this question without running this code in SQL Server 2012. I am very confident that irrespective of SQL Server version you are running you will have great learning. I will follow up of the answer in comments below. Recently my friend Vinod Kumar wrote excellent blog post on SQL Server 2012: Using SEQUENCE, you can head over there for learning sequence in details. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Get Schema Name from Object ID using OBJECT_SCHEMA_NAME

    - by pinaldave
    Sometime a simple solution have even simpler solutions but we often do not practice it as we do not see value in it or find it useful. Well, today’s blog post is also about something which I have seen not practiced much in codes. We are so much comfortable with alternative usage that we do not feel like switching how we query the data. I was going over forums and I noticed that at one place user has used following code to get Schema Name from ObjectID. USE AdventureWorks2012 GO SELECT s.name AS SchemaName, t.name AS TableName, s.schema_id, t.OBJECT_ID FROM sys.Tables t INNER JOIN sys.schemas s ON s.schema_id = t.schema_id WHERE t.name = OBJECT_NAME(46623209) GO Before I continue let me say I do not see anything wrong with this script. It is just fine and one of the way to get SchemaName from Object ID. However, I have been using function OBJECT_SCHEMA_NAME to get the schema name. If I have to write the same code from the beginning I would have written the same code as following. SELECT OBJECT_SCHEMA_NAME(46623209) AS SchemaName, t.name AS TableName, t.schema_id, t.OBJECT_ID FROM sys.tables t WHERE t.name = OBJECT_NAME(46623209) GO Now, both of the above code give you exact same result. If you remove the WHERE condition it will give you information of all the tables of the database. Now the question is which one is better – honestly – it is not about one is better than other. Use the one which you prefer to use. I prefer to use second one as it requires less typing. Let me ask you the same question to you – which method to get schema name do yo use? and Why? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL System Table, SQL Tips and Tricks, T SQL, Technology

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  • should I learn html/css before php even for using database? [on hold]

    - by Sadegh
    I saw lots of question about this topic and all of them were talking if someone want to use php for "building web pages", should learn html first or not. and most of them said yes, because most of the time you make web page with both php and html (and maybe css). But If I just want to use php for contacting to My Database (for example MySQL) and nothing more, shuold I learn any html or CSS first or not?

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  • Introduction à JPA, application au chargement de données depuis une base MySQL, par Thierry Leriche-Dessirier

    Bonjour à tous, Je vous propose un nouvel article rapide, intitulé "Introduction à JPA, application au chargement de données depuis une base MySQL" et disponible à l'adresse suivante : http://thierry-leriche-dessirier.dev...sql-jpa-intro/ Ce miniarticle montre (par l'exemple) comment charger des données depuis une base MySQL, à l'aide de JPA (Java Persistence API), en quelques minutes et en nous limitant aux fonctionnalités simples. Attention : La techno JPA (Java Persistence API) est relativement complexe. Dans cet article, nous n'abordons que les points faciles. Ceci n'est donc pas un tutoriel complet m...

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  • phpMyAdmin - Display all queries

    - by Carlos Fernández San Millán
    I have installed a fresh desktop with ubuntu quantal and the following packages versions: MySQL: 5.5.28-0ubuntu0.12.10.1 Apache: 2.2.22 (Ubuntu) phpMyAdmin: 3.4.11.1deb1 I would like phpmyadmin to display all the queries I run. How can I do it? Thank you very much. UPDATE To be more specific, there are some queries showing into the query box, but I would like phpMyAdmin to show ALL of them including when I export a Database (if possible). Thank you.

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  • Query a Log4Net-database

    - by pinhack
    So if you use Log4Net to log into a database (i.e. using the AdoNetAppender), how can you conveniently get an overview of what has happend ? Well, you could try the following Query ( T-SQL ):   SELECT convert(varchar(10),LogDB.Date,121) as Datum, LogDB.Level, LogDB.Logger,COUNT(LogDB.Logger) as Counter From Log4Net.dbo.Log as LogDB  where Level <> 'DEBUG' AND convert(varchar(10),LogDB.Date,121) like '2010-03-25' GROUP BY convert(varchar(10),LogDB.Date,121),LogDB.Level,LogDB.Logger ORDER BY counter desc This query will give you the number of events by the Logger at a specified date - and it's easy to customize, just adjust the Date and the Level to your needs. You need a bit more information than that? How about this query:  Select  convert(varchar(10),LogDB.Date,121) as Datum,LogDB.Level,LogDB.Message,LogDB.Logger ,count(LogDB.Message) as counter From Log4Net.dbo.Log as LogDB where Level <> 'DEBUG' AND convert(varchar(10),LogDB.Date,121) like '2010-03-25' GROUP BY convert(varchar(10),LogDB.Date,121),LogDB.Level,LogDB.Message,LogDB.Logger ORDER BY counter desc Similar to the first one, but inclusive the Message - which will return a much larger resultset.

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  • Database and query to store and retreive friend list [migrated]

    - by amr Kamboj
    I am developing a module in website to save and retreive friend list. I am using Zend Framework and for DB handling I am using Doctrine(ORM). There are two models: 1) users that stores all the users 2) my_friends that stores the friend list (that is refference table with M:M relation of user) the structure of my_friends is following ...id..........user_id............friend_id........approved.... ...10.........20 ..................25...................1.......... ...10.........21 ..................25...................1.......... ...10.........22 ..................30...................1.......... ...10.........25 ..................30...................1.......... The Doctrine query to retreive friend list id follwing $friends = Doctrine_Query::create()->from('my_friends as mf') ->leftJoin('mf.users as friend') ->where("mf.user_id = 25") ->andWhere("mf.approved = 1"); Suppose I am viewing the user no.- 25. With this query I am only getting the user no.- 30. where as user no.- 25 is also approved friend of user no.- 20 and 21. Please guide me, what should be the query to find all friend and is there any need to change the DB structure.

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  • Query something and return the reason if nothing has been found

    - by Daniel Hilgarth
    Assume I have a Query - as in CQS that is supposed to return a single value. Let's assume that the case that no value is found is not exceptional, so no exception will be thrown in this case. Instead, null is returned. However, if no value has been found, I need to act according to the reason why no value has been found. Assuming that the Query knows the reason, how would I communicate it to the caller of the Query? A simple solution would be not return the value directly but a container object that contains the value and the reason: public class QueryResult { public TValue Value { get; private set; } public TReason ReasonForNoValue { get; private set; } } But that feels clumsy, because if a value is found, ReasonForNoValue makes no sense and if no value has been found, Value makes no sense. What other options do I have to communicate the reason? What do you think of one event per reason? For reference: This is going to be implemented in C#.

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  • What is the disadvantage of using abstract class as a database connectivity in zend framework 2 instead of service locator

    - by arslaan ejaz
    If I use database by creating adapter with drivers, initialize it in some abstract class and extend that abstract class to required model. Then use simple query statement. Like this: namespace My-Model\Model\DB; abstract class MysqliDB { protected $adapter; public function __construct(){ $this->adapter = new \Zend\Db\Adapter\Adapter(array( 'driver' => 'Mysqli', 'database' => 'my-database', 'username' => 'root', 'password' => '' )); } } And use abstract class of database like this in my models: class States extends DB\MysqliDB{ public function __construct(){ parent::__construct(); } protected $states = array(); public function select_all_states(){ $data = $this->adapter->query('select * from states'); foreach ($data->execute() as $row){ $this->states[] = $row; } return $this->states; } } I am new to zend framework, before i have experience of working in YII and Codeigniter. I like the object oriented in zend so i want to use it like this. And don't want to use it through service locater something like this: public function getServiceConfig(){ return array( 'factories' => array( 'addserver-mysqli' => new Model\MyAdapterFactory('addserver-mysqli'), 'loginDB' => function ($sm){ $adapter = $sm->get('addserver-mysqli'); return new LoginDB($adapter); } ) ); } In module. Am i Ok with this approach?

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