We use the product DB Artisan for many of our dba tasks. When we use DB Artisan to migrate tables from unit test to system test, for example, the _WA_Sys... indexes are changed from indexes that do not appear on the DB Artisan list of indexes (in the source database) to ones that do appear in the DB Artisan list of indexes (in the target database).
1) I'm trying to find out if this subtle change in status for the statistics indexes harms their functioning for statistics use.
2) Also, does this subtle change in status for the indexes lead to performance problems such as increased response time.
3) Should we delete the _WA_Sys_ indexes in the target database and let the system create its own there?
Background:
With SQL-Server 7.0, certain indexes are automatically created. They have names that start with _WA_Sys_. They are used by SQL-Server 7.0 for statistics that SQL-Server uses for its decision making.
One place to find out more about these automatically created statistical 'indexes' is in SQL Server Books Online, part of the SQL-Server 7.0 package. Use the 'search' method and search for 'statistical information'. The first entry returned gives some information about the indexes that appear when the database option 'auto create statistics' is set to true.
I ran the sp_helpindex for a particular table on a CRM db and it returned with a list of 63 indexes, most of which had an index name beginning with _WA_Sys .. followed by what looked like a system generated name.
But when I open the design table in the EM and bring up a list of indexes, I don't find any of the indexes which begin with _WA_Sys .. listed.
I am running SQL 7, sp 2 on NT4, sp 6.
Any light on the anamoly ? Are they some temp indexes created by SQL 7 ?
After converting from SQL Server 6.5 to 7.0, there exist a number of indices in sysindexes with names starting with _WA_Sys_, e.g. _WA_Sys_PGJ_GROUP_JOB_ID_3EA749C6. When a Complete Compare is executed in ERwin, these indices are reported as variances to the data model. When a DROP INDEX statement is executed, SQL Server complains that the index isn't in the system catalog. The following is an example:
DROP INDEX ASSIGNED_INSERTER_SETUP._WA_Sys_PGJ_GROUP_JOB_ID_3 EA749C6 Cannot drop the index 'ASSIGNED_INSERTER_SETUP._WA_Sys_PGJ_GROUP_JOB_ID_ 3EA749C6', because it does not exist in the system catalog. General SQL Server error: Check messages from the SQL Server. Execution Failed!
How do we drop these indices? Thank you in advance for your assistance.
I'm working to improve performance on a database I've inherited, and there are several thousand indexes. I've got a list of ones which should definitely exist within the database, and I'm looking to strip out all the others and start fresh, though this list is still quite large (1000 or so).
Is there a way I can remove all the indexes that are not in my list without too much trouble? I.e. without having to manually go through them all individually. The list is currently in a csv file.
I'm looking to either automate the removal of indexes not in the list, or possibly to generate the Create statements for the indexes on the list and simply remove all indexes and then run these statements.
As an aside, when trying to list all indexes in the database, I've found various scripts to do this, but found they all seem to produce differing results. What is the best script to list all indexes?
So I'm reading http://www.sql-server-performance.com/tips/clustered_indexes_p2.aspx and I come across this: When selecting a column to base your clustered index on, try to avoid columns that are frequently updated. Every time that a column used for a clustered index is modified, all of the non-clustered indexes must also be updated, creating additional overhead. [6.5, 7.0, 2000, 2005] Updated 3-5-2004 Does this mean if I have say a table called Item with a clustered index on a column in it called itemaddeddate, and several non-clustered indexes associated with that table, that if a record gets modified and it's itemaddeddate value changes, that ALL my indexes on that table will get rebuilt? Or is it referring to the table structure changing? If so does this "pseudocode" example also cause this to occur: sqlstring="select * from item where itemid=12345" rs.open sqlstring, etc, etc, etc rs.Fields("ItemName")="My New Item Name" rs.Fields("ItemPrice")=1.00 rs.Update Note I didn't explicitly change the value of rs.fields("ItemAddedDate")...does rs.Fields("ItemAddedDate")=rs.Fields("ItemAddedDate") occur implicitly, which would force the rebuild of all the non-clustered indexes?
I have a requirement to only rebuild the Clustered Indexes in the table ignoring the non clustered indexes as those are taken care of by the Clustered indexes.
In order to do that, I have taken the records based on the fragmentation %.
But unable to come up with a logic to only consider rebuilding the clustered indexes in the table.
Does anyone have the idea why the Indexes with _WA.....(like _WA_Sys_au_fname_07020F21) gets created.I don't how this index got created. I did not create this Index. My Question is does the system creates these indexes or something else does this. Thanks Chak
Is there a way to tell how many indexes exist for an entire database, all I'm looking is for a count or generating a report list. any help would be appreciated, thank you
At present I have been assigned to create indexes to retrieve the information fast, from the table. The existing table doesn’t have primary key, foreign key and unique constraints but I found to many default indexes already created by the system. I would like to know how this happened? Please inform how to delete these default indexes. Further, inform me other possible ways for the faster retrieval in SQL sever 7.0, if there are any.
I would appreciate if you send me a step by step explanations for the above problems.
I have run into a snag on my development server. Queries that are selecting data based on indexed fields in a where clause are using the wrong indexes. They are arbitrarily using the clustered index which isn't in the select at all and causing big performance problems. I can run the same statements on my production server and it runs based on the proper indexes. I used query execution plans to determine that this was infact the case.
I run DBCC Checkdb everynight and it comes back with no errors. I also rebuild the indexes. We also don't receive any other errors inputting or updating data. This sounds like corruption to me but if it's something else I don't want to spend the night restoring from production if there is another reason.
Is there any way for me to find out when last indexes have been used so that the one I don't need can be dropped.And also the one's that are of no use at all. I need this as i am trying to dump all duplicated indexe . i know i can do this in ver 7
when executed sp_help tablename, I get lot of statistics and indexes like the following. Can anyone please tell me how it is generated automatically. as far i know statistics are generated only for primary keys. Can you please tell me what is clustered , hypothetical and the indexes starting with _WA supposed to be. Also there are lot of duplicate stats. Is it Ok to deletes those. _WA_Sys_is_platinum_0A9D95DB _WA_Sys_active_0A9D95DB nonclustered, statistics, auto create located on PRIMARY Active hind_c_33_15 nonclustered, statistics located on hind_c_37_1 clustered, hypothetical located
I have a question about speed and indexes. I have a static table (no updates except once a year). I want to be able to search data quickly on one column or many columns. I have created nonclustered indexes on each of the columns I search by. Is there anything else I can do to speed up my queries? Unfortunately all the searches involve using the like operator. I have even broken my table down into 2 smaller tables (Table A ~ 3 million rows, Table B 8 million rows).
I need to alphabetize PART of a union all query, and was told that this may be accomplished with an index. I tried joining two views, but it does not work! I have NO experience with indexes and need some help.
Here is my code:
Select id, country from countries where id = 6 union all Select id, country from countries where id <> 6
I want the country with id 6 (USA) to be the default on a drop down list, then all the other countries listed after it in alphabetical order. Can you do this with an index? If so, how do I proceed?
We recently updated some of the databases from MS Access 2000 to SQL Server 2000. In Access we had columns which were set to Indexed No Duplicates, these were not Primary key fields. Is this possible to set some indexes to prevent duplicates in SQL Server without creating performance issues?
Q1 The table i have stores max 2000 records. Not sure if i neeed a clustered index for this few records. I guess not.
Q2 For the same table as above. How do you create primary keys if there is not unique records. Do i create a new column? like newColumnID identity? and create a primary key on this new column? Ok even if i create this newcolumn. I don't think it will improve the retrieving speed cause i'm not selecting this column.
i am running a stored procedure which has got clustered indexes created after creating table and data is inserted into it after creating clustered indexes. The tables which are meant in this sp is temporary tables and how to gain the performance of a query
I've created indexes for the queries below running select getdate() before and after the query to determine the time. I'm curioius as to how sql server determines and decides how and when to use the indexes for the queries and how the run times of these queries compare. I'm also curious to know what kind of difference there would be on the last two queries as the only difference is the values. For the last two queries I don't think there would be a difference but hoping that someone would know.
Below are my results:
select count(distinct CustomerID) from Orders where Status = 5
SELECT getdate() go Create Index Orders_Index On Orders(customerID) go SELECT getdate()
select sum(TotalDue) from Orders where CustomerID = 11212
select getdate() go Create Index Orders_Index On Orders(customerID) go select getdate()
select count(distinct AccountNumber) from Orders where SalesPersonID = 288
select getdate() go Create Index Orders_Index On Orders(salespersonID) go select getdate()
select count(distinct AccountNumber) from Orders where SalesPersonID = 276
select getdate() go Create Index Orders_Index On Orders(salespersonID) go select getdate()
I have a very large table (about 200,000 records), but there are only 2 fields in the table only one populated with data. I need to update the 2nd field with the first field's data.
UPDATE Table1 SET field2 = field1
This is taking a really long time to run about 3.5 minutes. Is this normal? Can I create an index? What can I do to shorten the run time?
Aren't all indexes created as separate structures from a table? Although the index is created against a particular table, doesn't the index itself exist in the database as a separate, self-contained structure?
Which index type -- clustered or nonclustered -- logically sorts the database of a table?
I need some help in deciding for the best index design possible for my requirements. Well basically i have 3 tables (lets call it T1, T2 and T3 ). T1 is only used like a source... T2 is a source and destination... T3 is only a destination table.
Lets suppose all tables have the same columns structure. In the first phase i insert records from T1 into T2 using lots of different queries filters like this: WHERE Col1 = x AND Col2 IN (A and B) AND Col3 Between Int1 and Int2 AND Col4 = y
Other queries looks the same but diferent column is used in the Col4 place... so it can be Col5, 6 or 7 for example.
In the second phase i do the same but from T2 into T3...
Whats the best index design in this case?
Should i disable indexes in the destination table T2 while i am loading it and the rebuild? This can take alot of time, any other way? Is it best to leave it enabled all the time?
What kind of indexes should i create? Multi Column indexes or single ones for Col1, 2 3 4 5 6.. etc??
i have some confusions with keys and indexes.. plz let me know whether the following are correct..- Every Primary Key is a Clustered Index- A Primary Key cannot exist without a Clustered Index- Every Unique Key is a Non-Clustered Index - Non-Clustered Index is the DEFAULT Index- A table can have only 1 Primary key- A table can have only 1 Clustered Index- A table can have any number of Unique Keys- A table can have any number of Non-Clustered Indexes
Just a quick question, Is it better to build an Indexindicies after creating a new table or after populating the table with the data. Which is quicker? What about statistics? This table is dropped/and then recreated on a weekly basis. It is a reporting database.
