IRowsetIndex()::Seek In SQL CE
Jul 30, 2007
Dear All,
I'm working in eVC++3.0 with SQL CE2.0.
I've developed the application to fetch the data from the mdf file by passing the index field and using the command IRowsetIndex()::Seek.
Consider TableExample with Columns A,B,C,D and index Index1 with column A and Index2 with column B,C,D.
Its working fine when index1 is passed for the indexvalue.But when i pass index2 of the same table,its throwing the error as BADINDEX.
I'm passing the correct keyvalues in the Seek command also.
Kindly help me in this regard.
Regards,
Sasi.
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Dec 4, 2007
This doesn't seem to be documented anywhere.
When you call IRowsetIndex::GetIndexInfo, it allocates memory for an array of DBINDEXCOLUMNDESC structures, which the documentation says to free using IMalloc::Free. However it does not say to free the pColumnId member of each DBINDEXCOLUMNDESC (which is a DBID*), or the pointer members of pColumnId. I think that if you don't do this, you will have a memory leak.
I used the following code to completely free the DBINDEXCOLUMNDESC structures:
Code Block
inline void FreeDBIDMembers(DBID &dbid)
{
switch(dbid.eKind)
{
case DBKIND_GUID_NAME:
case DBKIND_NAME:
if(dbid.uName.pwszName != NULL)
CoTaskMemFree(dbid.uName.pwszName);
break;
case DBKIND_PGUID_NAME:
if(dbid.uName.pwszName != NULL)
CoTaskMemFree(dbid.uName.pwszName);
if(dbid.uGuid.pguid != NULL)
CoTaskMemFree(dbid.uGuid.pguid);
break;
case DBKIND_PGUID_PROPID:
if(dbid.uGuid.pguid != NULL)
CoTaskMemFree(dbid.uGuid.pguid);
break;
}
}
// Used to free memory allocated by IRowsetIndex::GetIndexInfo
inline void FreeDBINDEXCOLUMNDESC(DBINDEXCOLUMNDESC *pColDesc, ULONG nColumns)
{
if (!pColDesc)
{
return;
}
DBINDEXCOLUMNDESC *pColCur = pColDesc;
for(unsigned int i = 0; i < nColumns; ++i, ++pColCur)
{
if (pColCur->pColumnID)
{
FreeDBIDMembers(*pColCur->pColumnID);
CoTaskMemFree(pColCur->pColumnID);
}
}
CoTaskMemFree(pColDesc);
}
I used CoTaskMemFree rather than IMalloc::Free as I am working with Pocket PC. Thanks also to Joao Paulo Figueira who has documented a fix to a similar memory leak, which was my inspiration for finding and fixing this one! If you are using Figueira's CRowsetIndex, part of his adapted ATL OLEDB templates for Pocket PC, then you are likely to have this leaky code too.
Can anyone confirm this is correct?
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May 7, 2008
Hi,
Can I use index seek and still keep 'like' 'or' functionality for the following statement?
--prepare test table
create table entity (Id int identity(1,1), FamName varchar(200), LastName varchar(200))
go
create clustered index entity_id on entity (id)
go
create nonclustered index entity_lastName on entity (lastName)
go
insert into entity select famName,FirstName from table
--test index
declare @LastName varchar(10)
set @LastName = 'a'
select FamName
from entity
where @LastName is null or LastName like @LastName --clustered index scan
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Nov 4, 2002
I have created a nolock view off a table to prevent locks. I have users coming in through MS Access that have switched their queries to run against the views. Now we are noticing that queries that used to run as a clustered index seek against the table are running as a clustered index scan against the table and performance in the queries has dropped.
Is there any way that the same query that hits the view instead of the table can be made to run faster or at least use the index seek?
Thanks,
Steve
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May 18, 2006
Hello I want to seek and find the table named NewCustomer from the database so what would be the query ?
F16 LĂ?GHTĂ?NĂ?NNNG
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Dec 20, 2006
I have an MS Access 2003 database from which I want to seek a specific record in a SQL Server Express 2005 database. I can connect to the table and get a recordcount but the recordset.supports (adseek) and recordset.Supports(adIndex) both return false. Any suggestions? Specific code I'm using is as follows:
Dim cnxn As ADODB.Connection
Dim strCnxn As String
Set cnxn = New ADODB.Connection
cnxn.Provider = "sqloledb"
strCnxn = "Data Source=SERVERSQLEXPRESS2005;Initial Catalog=RAMPSQL;Integrated Security='SSPI';"
cnxn.Open strCnxn
Set rsWSC = New ADODB.Recordset
rsWSC.CursorLocation = adUseServer
strSQL = "DailyData"
rsWSC.Open strSQL, cnxn, adOpenKeyset, adLockReadOnly, adCmdTableDirect
Thank you!
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Nov 30, 2006
Hi
I have a frontend Access and backend SQL
works fine but when i in my customer table seek in name
it takes very very long time . I use ODBC to my connection
is there anayway to this better.?
regards
alvin
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Oct 4, 2007
Hi,
I am reading the book by Steven Roman:
"Access Database : Design and Programming" 3rd edition.
On page 120, Figure 7-2, he showed the the structure of the Jet Database Engine, which is very confusing to me.
According to this picture, I come to such an understanding:
1) VBA is just the hosting language for the Jet Database Engine;
2) Microsoft Visual Basic, Excel, Access, Word are hosting languages for VBA.
Isn't this weird? VB hosts VBA?
Thanks for any input!
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Jun 21, 2004
create table t1(a varchar(50) , b varchar(50))
create index i1 on t1(a)
create index i2 on t1(b)
create view v1
as
select * from t1 where isnull(a,b) = 'test'
select * from v1
The above SQL "select * from v1" is doing a table scan.
What do I do to make it perform an index seek ????
TIA
- ForXLDB
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Dec 13, 2007
Hi All,
The script below may be use to find out what stored procedure uses a specified column from any of the table. This could be helpful in cases you have change a field name of a table and want to find out what stored procedure uses that column.
create procedure seek_sp_for_columns
@colname_para varchar(500)
as
begin
create table #temp_t
(
textcol varchar(1000)
)
create table #temp_t2
(
procname varchar(500)
)
declare @procname as varchar(500)
declare @found as int
declare @colname as varchar(500)
declare @valid_colname as int
select @valid_colname = count(id)
from syscolumns
where name = @colname_para
if (@valid_colname > 1)
begin
set @colname = '%' + @colname_para + '%'
declare sp_cursor cursor
for select name
from sysobjects
where xtype = 'P'
open sp_cursor
fetch next from sp_cursor
into @procname
while @@fetch_status = 0
begin
insert into #temp_t
exec sp_helptext @procname
set @found = 0
select @found = count(textcol)
from #temp_t
where textcol like @colname
if (@found > 0)
begin
insert #temp_t2 values(@procname)
end
delete #temp_t
fetch next from sp_cursor
into @procname
end
close sp_cursor
deallocate sp_cursor
select *
from #temp_t2
drop table #temp_t
drop table #temp_t2
end
else
begin
select 'Please verify column name'
end
end
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Jul 23, 2005
From what I've read in the docs, ado.net currently supports opening sqlserver ce tables in table-direct mode and performing Seek operations on them(using SqlCeDataReader), but not on the full-blown sql server. Is this(will this be) still true with ado.net 2.0 & sql server 2005?
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May 11, 2006
I am getting error 0x80040E25 when I try to call seek after update on a Recordset opened as (adOpenStatic, adLockOptimistic, adCmdTableDirect)
9 - (13.250) - <2> - *** error in .DbRecordset.cpp, line 908
10 - (13.250) - <2> - ADO_ERRORS FOR pRs = 200a420, seek, err=-2147217883(80040e25)
11 - (13.250) - <2> - ADO_ERROR: E R R O R 1 of 1.
12 - (13.250) - <2> - ADO_ERROR: DESCRIPTION: All HROWs must be released before new ones can be obtained. [,,,,,].
13 - (13.250) - <2> - ADO_ERROR: NUMBER: 80040E25
14 - (13.250) - <2> - ADO_ERROR: NATIVE_ERROR: 0
15 - (13.250) - <2> - ADO_ERROR: SOURCE: Microsoft SQL Server 2005 Mobile Edition OLE DB Provider
I registered SQL Mobile 3.0 dlls using regsvr32.exe so now I can connect to SQLCE3.0 databases on desktop using plain ADO with such connection string _T("Provider=Microsoft.SQLSERVER.MOBILE.OLEDB.3.0; Data Source=") + name of the file
I have not asked this question before as it did not make sense -> there was no official SQLCE3.0 support on desktop. Now, since SQL CE is promiced to be supported on desktop as SQL/E I decided to ask.
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Dec 10, 2006
If you display the execution plan and run the following:SET STATISTICS IO ONgoSELECT ProductID, SupplierIDFROM ProductsWHERE SupplierID = 1I don't understand how come there is noBookmark Lookup operation happening to get theProductID?I only see an Index Seek happening on SupplierID.There is no composite index SupplierID + ProductIDso what am I not understanding here?Thank you
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Sep 19, 2015
I've been having some trouble getting a single-column "varchar(5)" field to reliably use a table seek instead of a table scan. The production table in this case contains 25 million rows. As impressive as it is to scan 25 million rows in 35 seconds, the query should run much faster.
Here's a partial table description:
CREATE TABLE [dbo].[Summaries_MO]
(
[SummaryId] [int] IDENTITY(1,1) NOT NULL,
[zipcode] [char](5) COLLATE Latin1_General_100_BIN2 NOT NULL,
[Golf] [bit] NULL,
[Homeowner] [bit] NULL,
[Code] .....
Typically, this table is accessed with a query that includes:
SELECT ...
FROM SummaryTable
WHERE ixZIP IN (SELECT ZipCode FROM @ZipCodesForMO)
This query insists on using a table scan. I've tried WITH (FORCESEEK) for example, but that just makes the query fail.
As I've investigated this issue I also tried:
SELECT * FROM Summaries WHERE ZipCode IN ('xxxxx', 'xxxxx', 'xxxxx')
When I run this query with 64 or fewer (actual, valid) ZIP codes, the query uses a table seek.But when I give it 65 or more ZIP codes it uses a table scan.
To summarize, the production query always uses a table scan, and when I specify 65 or more ZIP codes the query also uses a table scan. I'm wondering if the data type of the indexed column (Latin1_General_100_BIN2) is somehow the problem. I'll likely try converting the ZIP codes to an integer to see what happens.
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Oct 20, 2006
please explain the differences btween this logical & phisicall operations that we can see therir graphical icons in execution plan tab in Management Studio
thank you in advance
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Mar 1, 2004
I have a really strange problem.
I execute this query:
declare @cid int
set @cid = 2003227
select * from sales s, product p where p.product_Id = s.product_Id and customer_id = @cid
select * from sales s, product p where p.product_Id = s.product_Id and customer_id = @cid or @cid = 0
3 Million rows in sales, 120000 in product.
The first does and index seek, the second an index scan.
The execution plan reports that the scan takes 99.87% of the cost, and the seek takes 0.13%
This problem obviously gets worse the bigger the dataset / query /etc.
The reason I query this, is because it never used to take this long to do index scans. Is there something i can change, something i can fix?
Any help would be appreciated.
Josh
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Nov 14, 2006
the query:
SELECT a.AssetGuid, a.Name, a.LocationGuid
FROM Asset a WHERE a.AssociationGuid IN (
SELECT ada.DataAssociationGuid FROM AssociationDataAssociation ada
WHERE ada.AssociationGuid = '568B40AD-5133-4237-9F3C-F8EA9D472662')
takes 30-60 seconds to run on my machine, due to a clustered index scan on our an index on asset [about half a million rows]. For this particular association less than 50 rows are returned.
expanding the inner select into a list of guids the query runs instantly:
SELECT a.AssetGuid, a.Name, a.LocationGuid
FROM Asset a WHERE a.AssociationGuid IN (
'0F9C1654-9FAC-45FC-9997-5EBDAD21A4B4',
'52C616C0-C4C5-45F4-B691-7FA83462CA34',
'C95A6669-D6D1-460A-BC2F-C0F6756A234D')
It runs instantly because of doing a clustered index seek [on the same index as the previous query] instead of a scan. The index in question IX_Asset_AssociationGuid is a nonclustered index on Asset.AssociationGuid.
The tables involved:
Asset, represents an asset. Primary key is AssetGuid, there is an index/FK on Asset.AssociationGuid. The asset table has 28 columns or so...
Association, kind of like a place, associations exist in a tree where one association can contain any number of child associations. Each association has a ParentAssociationGuid pointing to its parent. Only leaf associations contain assets.
AssociationDataAssociation, a table consisting of two columns, AssociationGuid, DataAssociationGuid. This is a table used to quickly find leaf associations [DataAssociationGuid] beneath a particular association [AssociationGuid]. In the above case the inner select () returns 3 rows.
I'd include .sqlplan files or screenshots, but I don't see a way to attach them.
I understand I can specify to use the index manually [and this also runs instantly], but for such a simple query it is peculiar it is necesscary. This is the query with the index specified manually:
SELECT a.AssetGuid, a.Name, a.LocationGuid
FROM Asset a WITH (INDEX (IX_Asset_AssociationGuid)) WHERE
a.AssociationGuid IN (
SELECT ada.DataAssociationGuid FROM AssociationDataAssociation ada
WHERE ada.AssociationGuid = '568B40AD-5133-4237-9F3C-F8EA9D472662')
To repeat/clarify my question, why might this not be doing a clustered index seek with the first query?
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Oct 4, 2007
Hey,
what is the difference between Table Scan und Index Scan?
I find no difitions in the internet
Finchen
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Sep 21, 2007
Hi,
I want to know wht is a
TABLE SCAN
INDEX SCAN
INDEX SEEKand When they are used, Wht is the difference between all these.????
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