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sql server programming : Poor Execution Plan in SQL Server 2005
We have a database in SQL Server 2000. I made a copy of this database(mdf,ndf,ldf) and attached it to SQL Server 2005 on the same machine. When I try one particular SP in both of them, SQL Server 2000 performs almost 2.5 times faster than 2005. The execution plan in 2005 contains HASH physical operators while 2000 has much better plan. I'm wondered that why this can happen while all of indexes are exactly the same in both databases. A few days ago, I heard from a colleague that he had experienced bad performance after upgrading the database of a customer to SQL Server 2005. They were forced to move the database to 2000 again! I didn't believe it but now I'm experiencing a real one! Any help would be greatly appreciated. Leila
Hi Leila
Are you aware that upgraded databases have all of their index statistics disabled & that you have to either recompute statistics or rebuild the indexes before SQL Server 2005 will use any indexes? You didn't mention this, so perhaps youre problem is this simple? Regards, Greg Linwood SQL Server MVP http://blogs.sqlserver.org.au/blogs/greg_linwood [quoted text, click to view] "Leila" <Leilas@hotpop.com> wrote in message news:O12cNSL6GHA.4476@TK2MSFTNGP04.phx.gbl... > Hi, > We have a database in SQL Server 2000. I made a copy of this > database(mdf,ndf,ldf) and attached it to SQL Server 2005 on the same > machine. When I try one particular SP in both of them, SQL Server 2000 > performs almost 2.5 times faster than 2005. The execution plan in 2005 > contains HASH physical operators while 2000 has much better plan. I'm > wondered that why this can happen while all of indexes are exactly the > same in both databases. > A few days ago, I heard from a colleague that he had experienced bad > performance after upgrading the database of a customer to SQL Server 2005. > They were forced to move the database to 2000 again! I didn't believe it > but now I'm experiencing a real one! > Any help would be greatly appreciated. > Leila >
That should work ok assuming the DB isn't too big & you're not trying to
squeeze the task into a small window. Another option is to rebuild the indexes, which might achieve some defragmentation as well, but I'd try the first option you suggested first. Regards, Greg Linwood SQL Server MVP http://blogs.sqlserver.org.au/blogs/greg_linwood [quoted text, click to view] "Leila" <Leilas@hotpop.com> wrote in message news:eS%23qO0O6GHA.3952@TK2MSFTNGP04.phx.gbl... > Thanks Greg, > Do you mean if I perform: > UPDATE STATISTICS MyTable WITH FULLSCAN > on every table, will correct the problem? Or other statements must be used > for indexes?? > > > > > "Greg Linwood" <g_linwood@hotmail.com> wrote in message > news:epPHSOM6GHA.3508@TK2MSFTNGP06.phx.gbl... >> Hi Leila >> >> Are you aware that upgraded databases have all of their index statistics >> disabled & that you have to either recompute statistics or rebuild the >> indexes before SQL Server 2005 will use any indexes? You didn't mention >> this, so perhaps youre problem is this simple? >> >> Regards, >> Greg Linwood >> SQL Server MVP >> http://blogs.sqlserver.org.au/blogs/greg_linwood >> >> "Leila" <Leilas@hotpop.com> wrote in message >> news:O12cNSL6GHA.4476@TK2MSFTNGP04.phx.gbl... >>> Hi, >>> We have a database in SQL Server 2000. I made a copy of this >>> database(mdf,ndf,ldf) and attached it to SQL Server 2005 on the same >>> machine. When I try one particular SP in both of them, SQL Server 2000 >>> performs almost 2.5 times faster than 2005. The execution plan in 2005 >>> contains HASH physical operators while 2000 has much better plan. I'm >>> wondered that why this can happen while all of indexes are exactly the >>> same in both databases. >>> A few days ago, I heard from a colleague that he had experienced bad >>> performance after upgrading the database of a customer to SQL Server >>> 2005. They were forced to move the database to 2000 again! I didn't >>> believe it but now I'm experiencing a real one! >>> Any help would be greatly appreciated. >>> Leila >>> >> >> > >
Actually once I created a new database in SQL Server 2005 and imported
tables from 2000. Then generated index scripts from 2000 and applied to 2005. This way I think there must not be need to updating statistics. The performance improved a little but still the execution plan in 2005 is poor and about 2 or 1.5 times slower than 2000! [quoted text, click to view] "Greg Linwood" <g_linwood@hotmail.com> wrote in message news:%2304XchP6GHA.4064@TK2MSFTNGP03.phx.gbl... > That should work ok assuming the DB isn't too big & you're not trying to > squeeze the task into a small window. > > Another option is to rebuild the indexes, which might achieve some > defragmentation as well, but I'd try the first option you suggested first. > > Regards, > Greg Linwood > SQL Server MVP > http://blogs.sqlserver.org.au/blogs/greg_linwood > > "Leila" <Leilas@hotpop.com> wrote in message > news:eS%23qO0O6GHA.3952@TK2MSFTNGP04.phx.gbl... >> Thanks Greg, >> Do you mean if I perform: >> UPDATE STATISTICS MyTable WITH FULLSCAN >> on every table, will correct the problem? Or other statements must be >> used for indexes?? >> >> >> >> >> "Greg Linwood" <g_linwood@hotmail.com> wrote in message >> news:epPHSOM6GHA.3508@TK2MSFTNGP06.phx.gbl... >>> Hi Leila >>> >>> Are you aware that upgraded databases have all of their index statistics >>> disabled & that you have to either recompute statistics or rebuild the >>> indexes before SQL Server 2005 will use any indexes? You didn't mention >>> this, so perhaps youre problem is this simple? >>> >>> Regards, >>> Greg Linwood >>> SQL Server MVP >>> http://blogs.sqlserver.org.au/blogs/greg_linwood >>> >>> "Leila" <Leilas@hotpop.com> wrote in message >>> news:O12cNSL6GHA.4476@TK2MSFTNGP04.phx.gbl... >>>> Hi, >>>> We have a database in SQL Server 2000. I made a copy of this >>>> database(mdf,ndf,ldf) and attached it to SQL Server 2005 on the same >>>> machine. When I try one particular SP in both of them, SQL Server 2000 >>>> performs almost 2.5 times faster than 2005. The execution plan in 2005 >>>> contains HASH physical operators while 2000 has much better plan. I'm >>>> wondered that why this can happen while all of indexes are exactly the >>>> same in both databases. >>>> A few days ago, I heard from a colleague that he had experienced bad >>>> performance after upgrading the database of a customer to SQL Server >>>> 2005. They were forced to move the database to 2000 again! I didn't >>>> believe it but now I'm experiencing a real one! >>>> Any help would be greatly appreciated. >>>> Leila >>>> >>> >>> >> >> > >
Actually once I created a new database in SQL Server 2005 and imported
tables from 2000. Then generated index scripts from 2000 and applied to 2005. This way I think there must not be need to updating statistics. The performance improved a little but still the execution plan in 2005 is poor and about 2 or 1.5 times slower than 2000! [quoted text, click to view] "Greg Linwood" <g_linwood@hotmail.com> wrote in message news:%2304XchP6GHA.4064@TK2MSFTNGP03.phx.gbl... > That should work ok assuming the DB isn't too big & you're not trying to > squeeze the task into a small window. > > Another option is to rebuild the indexes, which might achieve some > defragmentation as well, but I'd try the first option you suggested first. > > Regards, > Greg Linwood > SQL Server MVP > http://blogs.sqlserver.org.au/blogs/greg_linwood > > "Leila" <Leilas@hotpop.com> wrote in message > news:eS%23qO0O6GHA.3952@TK2MSFTNGP04.phx.gbl... >> Thanks Greg, >> Do you mean if I perform: >> UPDATE STATISTICS MyTable WITH FULLSCAN >> on every table, will correct the problem? Or other statements must be >> used for indexes?? >> >> >> >> >> "Greg Linwood" <g_linwood@hotmail.com> wrote in message >> news:epPHSOM6GHA.3508@TK2MSFTNGP06.phx.gbl... >>> Hi Leila >>> >>> Are you aware that upgraded databases have all of their index statistics >>> disabled & that you have to either recompute statistics or rebuild the >>> indexes before SQL Server 2005 will use any indexes? You didn't mention >>> this, so perhaps youre problem is this simple? >>> >>> Regards, >>> Greg Linwood >>> SQL Server MVP >>> http://blogs.sqlserver.org.au/blogs/greg_linwood >>> >>> "Leila" <Leilas@hotpop.com> wrote in message >>> news:O12cNSL6GHA.4476@TK2MSFTNGP04.phx.gbl... >>>> Hi, >>>> We have a database in SQL Server 2000. I made a copy of this >>>> database(mdf,ndf,ldf) and attached it to SQL Server 2005 on the same >>>> machine. When I try one particular SP in both of them, SQL Server 2000 >>>> performs almost 2.5 times faster than 2005. The execution plan in 2005 >>>> contains HASH physical operators while 2000 has much better plan. I'm >>>> wondered that why this can happen while all of indexes are exactly the >>>> same in both databases. >>>> A few days ago, I heard from a colleague that he had experienced bad >>>> performance after upgrading the database of a customer to SQL Server >>>> 2005. They were forced to move the database to 2000 again! I didn't >>>> believe it but now I'm experiencing a real one! >>>> Any help would be greatly appreciated. >>>> Leila >>>> >>> >>> >> >> > >
[quoted text, click to view]
Leila wrote: > Actually once I created a new database in SQL Server 2005 and imported > tables from 2000. Then generated index scripts from 2000 and applied to > 2005. This way I think there must not be need to updating statistics. The > performance improved a little but still the execution plan in 2005 is poor > and about 2 or 1.5 times slower than 2000! > So, you're not TRULY comparing the performance of identical databases then. I would suggest comparing the 2005 execution plan for this query to that from 2000. What's different? Could you possibly have missed an index in your migration? It might be worth migrating the database properly, by doing a backup of the 2000 database, restoring it to 2005, and then updating the statistics. -- Tracy McKibben MCDBA
Thanks Greg,
Do you mean if I perform: UPDATE STATISTICS MyTable WITH FULLSCAN on every table, will correct the problem? Or other statements must be used for indexes?? [quoted text, click to view] "Greg Linwood" <g_linwood@hotmail.com> wrote in message news:epPHSOM6GHA.3508@TK2MSFTNGP06.phx.gbl... > Hi Leila > > Are you aware that upgraded databases have all of their index statistics > disabled & that you have to either recompute statistics or rebuild the > indexes before SQL Server 2005 will use any indexes? You didn't mention > this, so perhaps youre problem is this simple? > > Regards, > Greg Linwood > SQL Server MVP > http://blogs.sqlserver.org.au/blogs/greg_linwood > > "Leila" <Leilas@hotpop.com> wrote in message > news:O12cNSL6GHA.4476@TK2MSFTNGP04.phx.gbl... >> Hi, >> We have a database in SQL Server 2000. I made a copy of this >> database(mdf,ndf,ldf) and attached it to SQL Server 2005 on the same >> machine. When I try one particular SP in both of them, SQL Server 2000 >> performs almost 2.5 times faster than 2005. The execution plan in 2005 >> contains HASH physical operators while 2000 has much better plan. I'm >> wondered that why this can happen while all of indexes are exactly the >> same in both databases. >> A few days ago, I heard from a colleague that he had experienced bad >> performance after upgrading the database of a customer to SQL Server >> 2005. They were forced to move the database to 2000 again! I didn't >> believe it but now I'm experiencing a real one! >> Any help would be greatly appreciated. >> Leila >> > >
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