Number order by NumbersTable. Number desc;. I was expecting the long running query to be killed after 2 minutes to allow the Index Rebuild to happen. Either this is not meant to resolve the AlwaysOn blocking issues or I am not doing the test right… Would be great to hear if anyone has managed to get this one to work. Thanks Kendra!
I guess I will have to develop my own in house solution for this issue pain. Longrunning transactions on secondary replicas can also block ghost cleanup from running in the primary and cause other perf issues, so having some way to detect and alert on those queries can come in handy.
Got it. Why not just do that? The results, if any, should be discarded. Thanks again Kendra. I think you may be on to something. Any final thoughts on Stats updates across a DataWarehouse?
I see so much conflicting advice out there on this topic in a Very Large Table Billions of Rows environment. Fillfactor might be an option.
It does vary quite a lot by environment. Been there! Later on that will help someone else or even you figure out if that maintenance is choice is still the best one.
Kendra I would like to try and see how fragmentation affects disk reads. For instance if I turn Statstics IO on and run a query would I see changes in reads as fragmentation grows?
Would I have to free the cache to do so? Perhaps the DMV sys. For queries you can run yourself: Statistics IO will break it down and show you logical and which of those were physical vs readahead. For a dev system: For sys. Where it gets tricksy: You might actually see fewer reads due to an execution plan change brought on as a side effect, rather than the actual compaction of the pages. Are there any rule-of-thumb numbers for how much these should be, perhaps by type of system? One interesting thing is that the wasted space is not entirely from index fragmentation: it might be from heaps you can get weird trapped space in these , or it might be from having rebuilt a lot of indexes with a LOWER fillfactor.
The reason given is that the indexes and statistics are partly based on available CPU and memory resources. I have not read that advice anywhere and am looking for a second source before making it part of my practices. Does that advice make sense to you? Changing the amount of memory available, the number of CPUs available, or the settings that control those max server memory, cost threshold for parallelism, max degree of parallelism can absolutely change your query plans.
But as soon as any of those things are changed, SQL Server knows that it has to reconsider all the execution plans: no index maintenance or statistics update is required to trigger that. What would be the impact if rebuild Index job stopped? Using SQL standards edition bit. Thanks Kendra… I thought if I run built-in rebuild index from maintenance plan and stop the job or cancelled then possibly index get corrupted that in running at the time got stopped.
Possibly queries might perform differently after a while. Any impact on table data? If you never run index maintenance, potentially your tables could become very fragmented and have a lot of empty space in them after a long time. Appreciate any advice on troubleshooting. I have a ETL process that always runs extremely long the next day after the rebuild or reorganize.
After the first day it returns to normal time around 1. I have a converted mainframe application that sadly still using cursors, everywhere! So we have enterprise edition SQL and we are doing all maintenance plans with online, and we try to use reorganize as much as we can. As we are getting that above error occasionally with the maintenance plans we have setup.
I have 1. The rebuild job is run against the database every night. The logic is simple — run select from sys. I am a bit confused, what are my options. Continue splitting the job into smaller chunks?
Should offline rebuild be faster? Or maybe hardcode all indexes and rebuild them anyway? Egor — lemme zoom back a little. Why are you doing index rebuilds every night on a 1. Soooo, I guess I should rebuild them to zero fragmentation. And then look how fast they get fragmented again? Well, I solved the problem. So all indexes get refreshed every 4 days. Step by step i check index fragmentation and Judging on it i choose to do rebuild or reorgonize.
Else I skip that index, and throw an alert into notification mail. Unicorns —is this site a joke or what….. Can we dispense with the silliness please. It hides the message. Serious —this reads like a 13 year old wrote it. You guys need to dispense with foolery. Cut it down —edit it for content and clarity. Nobody is going to read this site. Our tens of thousands of subscribers and followers are surely just bots trying to sell us Viagra.
I can totally see why you, fnguy yahoo. Thank you so much for turning my life around. Today is gonna be a brand new day! Shame on you.
It picks up the index has an issue but then does reorganize on just one partition leaving the rest fragmented. We are contacting him to see if he knows there appears to be significant bug in the code. But other times it missed the index entirely and other times its doing a single partition when in fact all the partitions need to be done.
Seriously, thanks for posting this. Just trying to find what the best plan of attack is to put around the heavier use times…etc. An update from the front lines of Troll slaying…or was that goblins?
I seem to have trouble telling them apart until my sword glows…. So batch updates were causing re-fragmentation of the warp coils right away leading me to assume the script was at fault.
Is it possible Kendra time travelled back to this point in time just for this very purpose? We may never know. Hi kendra, I have 1TB size database. Does rebuild job supersede index reorg? Appreciate your help on this. Enjoy the journey!
The only way I was able to fix the situation was to drop and recreate the index. Have you ever witnessed a similar behavior? That way you can get a rapid answer from the next available person rather than waiting for a single person who might not have had that same experience. I have a question on index reporg.. Since those are small tables page count is not more than How do i get the fragmentation reduced?
Does this fragmentation really cause slowness to the application? It runs through the leaf level of the index, andas it goes it fixes physical ordering of pages and also compacts pages to apply any previously set fillfactorsettings. You have to be careful how you read that, though. Reorganize will always try to do things within the space allocated. You should do a Rebuild instead for cases like these.
Hi, Brent Ozar! Thank you for the great article! No blocking with users requests. Transactions working only on the cluster mentined. If waits look normal, it sounds like something is throttling. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.
The Curious Case of… used to be part of our bi-weekly newsletter but we decided to make it a regular blog post instead so it can sometimes be more. Paul Randal August 3, Space Required Rebuilding an index requires building a new index before dropping the old index, regardless of the amount of fragmentation present in the old index.
Transaction Log Generated In the FULL recovery mode, an index rebuild is fully logged, so the transaction log will have to accommodate the full size of the index in a single transaction. Locks Required An offline index rebuild of any index holds a schema-modification i. Progress Reporting or Not Index rebuilds do not have proper progress reporting.
Statistics An index rebuild will always rebuild the index column statistics with the equivalent of a full scan or sampled, for an index partition or if the index is partitioned. Reorganize is always single-threaded. Rebuild can be multi-thread in Enterprise Edition only. Hi Paul, Great article, thanks for that. How does the SQL server do this? Because the inserts into the new index are separate transactions. It is nice to get some understanding on the options when rebuilding indexes.
Is there a low size limit for rebuilding the indexes? Hi Paul Can you provide the link for what does rebuild index does internally. No idea — something must have been blocking it. What were the waits from the reorg SPID? Hi Paul, Any suggestion on what to check in that scenario?
Leave a Reply Cancel reply Your email address will not be published. God Bless You. My project environment is on AlwaysOn sql server, I am planning to setup index rebuild and reorganize maintenance jobs. I just wanted to leave this appreciative comment, Keep up to good work man, there is many people that appreciate it.
We are experiencing the performance issues in production region sql server r2 when we moved from rebuild job full re-index offline to reorganize job smart index. In rebuild job full re-index offline some of the queries are good performance query This will run non business hours execution time taken less than 1. But after implementing the reorganize job from rebuild job same query has been taken most of the days more than minutes. If the index does not support rebuilding online then the index is reorganized.
Highly fragmented indexes can also be rebuilt offline optional. Please help me i am not a DBA. Thank you.
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