RE: How can I make this more efficient? (combining DataSet results with the results of a DB lookup.)
- From: stcheng@xxxxxxxxxxxxxxxxxxxx (Steven Cheng [MSFT])
- Date: Mon, 21 Jul 2008 03:54:01 GMT
Hi KF,
Based on your description, I understand that you have a DataSet/DataTable
generqted via some query from index server. And since each of the record
may have some additional data/fields in database, currently you're
performing a data access query from database server when looping each of
the DataSet/DataTable record, correct?
Yes, I can see that there does be some performance overhead when the record
count is quite large. In my opinion, I think you can consider the following
approaches to impove the query performance(both of them require more memory
space since you'll need to cache those additional fields locally in memory).
1. Before you loop the first Dataset/DataTable(generated from index server
), you can perform another query against the database which return all the
necessary records(contain the required additional fields), you can sort
them via the primary key(you want to search against later), this sort is at
T-SQL level. You can also sort it in DataTable , but I think T-SQL layer
will be more efficient:
#DataTable..::.Select Method
http://msdn.microsoft.com/en-us/library/system.data.datatable.select.aspx
#Filtering and Sorting with the DataTable Select Me
http://www.developerfusion.co.uk/show/4703/2/
After that , you get a sorted record sequence in memory (based primarykey).
Later in your code which loop each record in the index server records, you
can perform a binary search like approach in the returned records set above.
2. If the data in database is quite simple(not many fields), you can even
directly store all the fields into hashtable based on the certain primary
key. Later you can directly access HashTable for the requied data. This is
extremely quick and efficient.
Sincerely,
Steven Cheng
Microsoft MSDN Online Support Lead
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--------------------
From: "Ken Fine" <kenfine@xxxxxxxxxxxxxxxx>with the results of a DB lookup.)
Subject: How can I make this more efficient? (combining DataSet results
Date: Fri, 18 Jul 2008 15:25:18 -0700
is
This is a question that someone familiar with ASP.NET and ADO.NET DataSets
and DataTables should be able to answer fairly easily. The basic question
how I can efficiently match data from one dataset to data in a secondand
dataset, using a common key. I will first describe the problem in words
then I will show my code, which has most of the solution done already.second
I have built an ASP.NET that queries an Index Server and returns a DataSet
corresponding to a bunch of PDF files. I bind this DataSet to an ASP.NET
gridview, but I want to include more information than is in Index Server
alone (and no, I don't want to use IS custom properties, nor do I want to
use MSFT's great new free search server quite yet.) . I want to do a
database lookup to gather more information and I have a good idea how todo
that. I have successfully manually added extra columns to my DataSet'swhich
datatable and populated them with database data in an inefficient way
I will describe in the next paragraph.those
The filenames associated with the PDFs in the Index Server index include
database Primary Keys and my application parses those keys out. I use
primary keys to subsequently do a second collection of database lookups.sucks
Currently just for test purposes I have the application doing dozens of
lookups: it's querying the database on each iteration of a loop. This
from a performance standpoint. In anticipation of doing a single query offunctional
all necessary lookups, I have made it so that the system builds a
SQL query string that pulls all necessary records with additional metadata.use
What I need to know is:
1) Syntax for creating a new dataset based on my SQL string. I normally
the EntitySpaces ORM framework so my experience with Datasets is very weak.an
2) How to match the parts of the new dataset into my existing dataset in
EFFICIENT way. My code below will show a successful solution based on avery
INEFFICIENT way, using repeated lookups. I expect the solution willinvolve
repeated filterings of the single dataset based on the primary key.data
Now to my existing, inefficient code. I will walk you through it.
// Filling a DataSet called results, and manually adding some additional
columns to it:
if (dbAdapter != null) dbAdapter.SelectCommand.CommandText =
GetUwitmPdfArchiveQuery;
DataSet ds = new DataSet("Results");
dbAdapter.Fill(ds);
DataColumn dcolColumn = new DataColumn("ChrisSummary",
typeof(string));
ds.Tables[0].Columns.Add(dcolColumn);
DataColumn dcolColumn2 = new DataColumn("ChrisTitle",
typeof(string));
ds.Tables[0].Columns.Add(dcolColumn2);
DataColumn dcolColumn3 = new DataColumn("PublicationTitle",
typeof(string));
ds.Tables[0].Columns.Add(dcolColumn3);
DataColumn dcolColumn4 = new DataColumn("OriginalArticleUrl",
typeof(string));
ds.Tables[0].Columns.Add(dcolColumn4);
// [empty variables are initialized]
// start looking through the datarows. There is a DB primary key in the
one of the columns of the datarow . I grab that key and assign it the nameDB
tempInt
foreach (DataRow dr in ds.Tables[0].Rows)
{
int tempInt =
Convert.ToInt32(dr[4].ToString().Replace(".pdf", ""));
try
{
// I start concatenating a SQL string of all of the primary keys
listOfIds = listOfIds + " OR ContentID ='" +
dr[4].ToString().Replace(".pdf", "") + "'";
// This is the inefficient part. I'm using that key along with my
EntitySpaces ORM framework to do lookups each time this loop is iterated,
and populate my manually added rows. I want instead to do a single lookup
and use a second filtered DataSet to populate my manually added rows with
information. So I'm going to have to loop through once to get enough infoto
build my SQL string, then do something else to build the DataSet I need.SQL
This is where I need the help.
Contentitems ci = new Contentitems();
ci.LoadByPrimaryKey(Convert.ToInt32(tempInt));
dr["OriginalArticleUrl"] = ci.ConUrl;
dr["ChrisSummary"] = ci.ConSummary;
dr["ChrisTitle"] = ci.ConTitle;
dr["PublicationTitle"] = ci.ConSource;
// I finish my SQL statement and whack off some extraneous stuff from my
string
listOfIds = listOfIds.Substring(0, listOfIds.Length - 25);
string sqlQueryIds = "Select * From Contentitems WHERE
ContentID='99999999' " + listOfIds;
Would very much appreciate help making the above code efficient! Thanks!!!
-KF
.
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