SELECT command very slow with ADO 
Author Message
 SELECT command very slow with ADO

Hi,

DAO and ADO are totally differen technologies. DAO is
native to Access and uses its advantages. ADO is more
commont technology and is not oriented to particular type
of database. In some cases you can expect worse
performance then with DAO. But in many cases it depends on
how you implemented your code. In your particular case
when you open recordset using "SELECT * FROM Macros" SQL
statement it could take some time, because ADO retrieves
all records with all fields and transfers all this
information to client side. The main idea in that case
could be to select only records and fields, which you
really need in that particular moment. It will reduce time
of retrieving and transferring data from database to
client side. Also you can play with LockType, CursorType
and CursorLocation properties of recordset to improve
performance. For example if you are opening forward-only,
read-only cursor, then it work faster then oter types of
it.

Val

Quote:
>-----Original Message-----
>Hi everybodyand thanks in advance!

>I hope I can get a little help from you!
>I wanted to changed my code from DAO to ADO due to the

poor performance that
Quote:
>DAO has in some cases.

>I have a quiet simple code that accesses a database and
perfoms inserts and
>updates. Due to a not very good database design some

tables have up to 255
Quote:
>fields. With DAO there was no problem accessing these
tables with SQL
>commands, but the problem came when updating or inserting
records. This took
>up to 10 secs for a record of a table.

>When we changed to ADO we thought our problems would be
solved. We have
>changed some code but the performance is worse than with
DAO when executing
>SELECT commands. It has improved a lot when updating or
inserting records.

>I enclose the code and an example project and hope you
can give us a hint.

>The commands we want to execute are as simple as you will
see, regular
>updating or accessing of single records in a table but
with a large number
>of fields

>    Dim rst As New ADODB.Recordset
>    Dim fld As ADODB.Field
>    Dim Data As String
>    Dim i As Integer
>    Dim Index As Integer
>    Dim arrayData() As String

>    Debug.Print "Before SQL " & Time 'Print time before
sql

>    'Make de sql to get all values of Macros table, we
are not sure if
>    'the CursorType and LockType paramenters are correct
>    rst.Open "SELECT * FROM Macros", cnn, adOpenKeyset,
adLockOptimistic
><====With 255 fields takes 10 seconds !!!!!

>    Debug.Print "After SQL " & Time 'Print time after sql

>    Index = 1

>    ReDim arrayData(1 To rst.Fields.Count) 'reserve an
array to introduce
>values of data

>    'Introduce the values of data to an array
>    While Not rst.EOF
>        For Each fld In rst.Fields
>            Data = fld.Value
>            arrayData(Index) = Data
>            Index = Index + 1
>        Next
>        rst.MoveNext
>    Wend

>    rst.Close   'Close recorset

>    ViewData = arrayData   'return as a result of

function the array of data

- Show quoted text -

Quote:

>Thanks in advance

>ion+



Sun, 27 Jun 2004 00:38:34 GMT
 SELECT command very slow with ADO

See the following Knowledge Base articles for more information on
performance and migrating from DAO to ADO:

Q225048: INFO: Issues Migrating from DAO/Jet to ADO/Jet
http://support.microsoft.com/support/kb/Articles/q225/0/48.asp

Q247613: Slow Performance in Jet 3.51 When Editing Recordset from SELECT
http://support.microsoft.com/support/kb/Articles/q247/6/13.asp

Q240434: HOWTO: Improve Performance of Applications Using Jet 4.0
http://support.microsoft.com/support/kb/Articles/q240/4/34.asp

Hope these help!

Steven Bras, MCSD
Microsoft Developer Support/Visual Basic WebData

This posting is provided "AS IS" with no warranties, and confers no rights.

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Mon, 28 Jun 2004 02:44:22 GMT
 
 [ 2 post ] 

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