Search database with textbox - sql-server

Question

First of all I am working at VB 2012.
I have problem with searching my database. It goes so slow, actually filling the ListView is what bothers me.
I have a text box with TextChange event. Its instant search. So when I'm starting to write in that text box it's starts to filter the database and filling the data in the ListView.
This is the code in text box and the Load procedure
Private Sub txtID_TextChanged(sender As Object, e As EventArgs) Handles txtID.TextChanged
Load("SELECT * FROM table WHERE id LIKE '" & txtID.Text & "%'")
End Sub
Private Sub Load(ByVal strQ As String)
List.Items.Clear()
cmd = New SqlClient.SqlCommand(strQ, con)
dr = cmd.ExecuteReader()
If dr.HasRows = True Then
While dr.Read
Dim X As ListViewItem
X = List.Items.Add(dr(0))
X.SubItems.Add(dr(2))
X.SubItems.Add(dr(3))
X.SubItems.Add(dr(4))
X.SubItems.Add(dr(1))
X.SubItems.Add(dr(5))
End While
End If
End Sub
So, every time I hit a letter it calls the load procedure.
And I have so much data and it goes so slow. Can you help me somehow ? Is there any solution ?

Answer 1

I don't know how you're ever going to possibly speed that up. Connecting and querying the database is a lot of overhead, especially compared to the speed of pressing a key or typing a word. There's just not a way to do this without severely affecting the user who's typing.
What I suggest instead is that you wait for the user to tell you they're done typing before you bother making a search. If you're trying to do fancy auto-completion stuff you're going to need to cache the data a lot closer to the app than the database.

Answer 2

You need to create a class to hold the search results, like this:
Public Class SearchResult
Private _propID As String
Public Property ID() As String
Get
Return _propID
End Get
Set
_propID = Value
End Set
End Property
Private _propName As String
Public Property PropName() As String
Get
Return _propName
End Get
Set
_propName = Value
End Set
End Property
...
End Class
Now you query the database to get all the results to display in the list view, storing it in a List(Of SearchResult), like this:
Private Function Load(ByVal strQ As String) As List(Of SearchResult)
Dim ListOfResults = New List(Of SearchResult)
cmd = New SqlClient.SqlCommand(strQ, con)
dr = cmd.ExecuteReader()
If dr.HasRows = True Then
While dr.Read
Dim X As New SearchResult()
X.PropID = dr(0)
X.PropName = dr(1)
...
End While
End If
End Sub
You can call this code like this:
Dim AllSearchResults = Load("SELECT * FROM table WHERE id LIKE '" & txtID.Text & "%'")
Now when you want to do a search you can apply the following LINQ against your cached list of everything (AllSearchResults), like this:
Public Function DoSearch(searchText As String) As List(Of SearchResult)
Return From s In AllSearchResults Where s.PropID.Contains(searchText) Select c
End Function
Finally, you can call this LINQ filtering on each key press by the user, like this:
Private Sub txtID_TextChanged(sender As Object, e As EventArgs) Handles txtID.TextChanged
DoSearch(txtID.Text)
End Sub

Answer 3

One way to cut the overhead down by a fair degree to to wait to issue the query until the length of the text entered is 3 (or better yet 5) characters. It is very, very unlikely that all customers (or whatever these are) starting with 'S' is going to be meaningful or helpful to anyone except the one person on rare occasions looking for "Sab....". People HAVE to be typing in the 2nd and 3rd char before the first query is complete and displayed!
To try to make a really bad idea less bad, I'd look into a way to issue the query ONCE (on the first character if I really, really has to), then filter those results down on subsequent keystrokes. (ala Aaron's "caching the data a lot closer to the app").
The next thing is Select *. I dunno whats in the table, but do you REALLY need every column? This appears to be some sort of pick list, do you really need 6 fields to provide the user the information needed to make a selection? If there are more than 6 columns in the table, immediately narrow the query to the 6 used in the listview. Once they make their choice you can go back and get exactly what you need by ID or whatever.
I'd personally use a faster control but thats subjective.
ALL databases eventually acquire dormant data. Customers (or whatever) that were one time shoppers and never return - do they need to be in the list? If there is a column somewhere for lastorderdate or lastupdateddate construct your query to pick those active in the last XX months (and if not, see if you can add one because the issue is not going to get better as the database gets larger!). Then a checkbox for the user to widen the range as needed, like "See All" or something. Users are not likely to balk at the idea if it speeds things up the other 80% of the time.
...those are just off the top of my head.