I have this code
using (var contents = connection.CreateCommand())
{
contents.CommandText = "SELECT [subject],[note] FROM tasks";
var r = contents.ExecuteReader();
int zaehler = 0;
int zielzahl = 5;
while (r.Read())
{
if (zaehler == zielzahl)
{
//access r["subject"].ToString()
}
zaehler++;
}
}
I want to make it faster by accessing zielzahl directly like r[zielzahl] instead of iterating through all entries. But
r[zielzahl]["subject"]
does not work aswell as
r["subject"][zielzahl]
How do I access the column subject of result number zielzahl?
To get only the sixth record, use the OFFSET clause:
SELECT subject, note
FROM tasks
LIMIT 1 OFFSET 5
Please note that the order of returned records is not guaranteed unless you use the ORDER BY clause.
Related
I tried to count num of rows in grid in runtime with this code
FormRun caller;
FormDataSource fds;
QueryRun queryRun;
int64 rows;
fds = caller.dataSource();
query = fds.query();
queryRun = new QueryRun(query);
rows = SysQuery::countTotal(queryRun); //this returns -1587322268
rows = SysQuery::countLoops(queryRun); //this returs 54057
The last line of code is closest to what i need because there are 54057 lines but if i add filters it still returns 54057.
I want logic to get the number rows that grid has in the moment of calling the method.
Your query has more than one datasource.
The best way to explain your observation is to look at the implementation of countTotal and countLoops.
public client server static Integer countTotal(QueryRun _queryRun)
{
container c = SysQuery::countPrim(_queryRun.pack(false));
return conpeek(c,1);
}
public client server static Integer countLoops(QueryRun _queryRun)
{
container c = SysQuery::countPrim(_queryRun.pack(false));
return conpeek(c,2);
}
private server static container countPrim(container _queryPack)
{
...
if (countQuery.dataSourceCount() == 1)
qbds.addSelectionField(fieldnum(Common,RecId),SelectionField::Count);
countQueryRun = new QueryRun(countQuery);
while (countQueryRun.next())
{
common = countQueryRun.get(countQuery.dataSourceNo(1).table());
counter += common.RecId;
loops++;
}
return [counter,loops];
}
If your datasource contains one datasource it adds count(RecId).
countTotal returns the number of records.
countLoops returns 1.
Pretty fast, as fast as the SQL allows.
If your datasource contains more than one datasource it does not add count(RecId).
countTotal returns the sum of recIds (makes no sense).
countLoops returns the number of records.
Also countLoops is slow if there are many records as they are counted one by one.
If you have two datasources and want a fast count, you are on your own:
fds = caller.dataSource();
queryRun = new QueryRun(fds.queryRun().query());
queryRun.query().dataSourceNo(2).joinMode(JoinMode::ExistsJoin);
queryRun.query().dataSourceNo(1).clearFields();
queryRun.query().dataSourceNo(1).addSelectionField(fieldnum(Common,RecId),SelectionField::Count);
queryRun.next();
rows = queryRun.getNo(1).RecId;
The reason your count did not respect the filters was because you used datasource.query() rather than datasource.queryRun().query(). The former is the static query, the latter is the dynamic query with user filters included.
Update, found some old code with a more general approach:
static int tableCount(QueryRun _qr)
{
QueryRun qr;
Query q = new Query(_qr.query());
int dsN = _qr.query().dataSourceCount();
int ds;
for (ds = 2; ds <= dsN; ++ds)
{
if (q.dataSourceNo(ds).joinMode() == JoinMode::OuterJoin)
q.dataSourceNo(ds).enabled(false);
else if (q.dataSourceNo(ds).joinMode() == JoinMode::InnerJoin)
{
q.dataSourceNo(ds).joinMode(JoinMode::ExistsJoin);
q.dataSourceNo(ds).fields().clearFieldList();
}
}
q.dataSourceNo(1).fields().clearFieldList();
q.dataSourceNo(1).addSelectionField(fieldNum(Common,RecId), SelectionField::Count);
qr = new QueryRun(q);
qr.next();
return any2int(qr.getNo(1).RecId);
}
I'm trying to implement a table valued function (as a SQLite virtual table).
It's a function that would take a string and return a table with all the words of the string.
If I call it with literal values like below, it works fine.
SELECT word FROM splitstring("abc def ghi")
If, however, I call it with a column from another table it doesn't work:
SELECT a.Name, word FROM article a, splitstring(a.Text)
The xBestIndex method gets called all right, but right after that, I get an exception from the ExecuteReader method. The exception message is "xBestIndex malfunction". The xFilter method does not get called because of the exception.
My xBestIndex implementation is simple, it just marks the parameter so I can see it in xFilter:
public override SQLiteErrorCode BestIndex(SQLiteVirtualTable table, SQLiteIndex index)
{
index.Outputs.ConstraintUsages.ElementAt(0).argvIndex = 1;
index.Outputs.ConstraintUsages.ElementAt(0).omit = 1;
return SQLiteErrorCode.Ok;
}
Am I'm doing something wrong or is it impossible to pass non-literal parameters to table valued functions?
Found the issue! I was using constraints that had usable=0. The BestIndex method gets called multiple times by SQLite, the second time with a non-usable constraint.
Here is the fixed body of the BestIndex method.
public override SQLiteErrorCode BestIndex(SQLiteVirtualTable table, SQLiteIndex index)
{
if (index.Inputs.Constraints.Count() != 2)
throw new ArgumentException("The generate_series function requires two integer (long) parameters!");
if (index.Inputs.Constraints.All(c=>c.usable == 1))
{
index.Outputs.ConstraintUsages.ElementAt(0).argvIndex = 1;
index.Outputs.ConstraintUsages.ElementAt(0).omit = 1;
index.Outputs.ConstraintUsages.ElementAt(1).argvIndex = 2;
index.Outputs.ConstraintUsages.ElementAt(1).omit = 1;
}
else
{
index.Outputs.IndexNumber = -1;
index.Outputs.EstimatedCost = double.MaxValue;
}
return SQLiteErrorCode.Ok;
}
Now I check the usable flag. When BestIndex gets called with a constraint with usable=0 I skip it i.e. return a high estimated cost for that index so it doesn't get used.
This pertains to .NET Web Performance Tests.
If I have an ASP.NET page with a GridView that has a column of ints, how do I write an extraction rule to get the largest int in the column?
I tried creating a custom extraction rule by inheriting from ExtractionRule and in the Extract method using e.Response.HtmlDocument.GetFilteredHtmlTags however, the HtmlTags returned don't seem to expose their innerHtml contents.
Perhaps you can write an extraction rule that gets the whole column, then process the numbers to get their maximum value. Alternatively, use a built-in extraction rule to get the whole column, then write a plugin to get the maximum value. In either case your code should expect a mixture of numbers and other text.
Ben Day has a great blog post containing two types that express similar concerns. TableColumnValueValidator and ExtractRandomValueFromTable.
http://www.benday.com/2013/08/19/validation-extraction-rules-for-visual-studio-2012-web-performance-tests/
In the Extract(object, ExtractionEventArgs), you need to parse the ExtractionEventArgs.Response.BodyString. Ben uses the HtmlAgilityPack library for this. http://www.nuget.org/packages/htmlagilitypack
Something like this is roughly the code you'd need. This is simliar logic to ExtractRandomValueFromTable.
This does not account for thead/tbody or cells that span multiple columns/rows.
HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
doc.LoadHtml(e.Response.BodyString);
HtmlNode table = doc.GetElementbyId(TableId); // TableId is a test property
HtmlNodeCollection columns = table.SelectNodes("//th");
int columnIndex = FindColumnIndexByName(columns, ColumnName); // ColumnName is a test property
HtmlNodeCollection rows = table.SelectNodes("//tr")
int maxValue = Int32.MinValue;
foreach(HtmlNode row in rows)
{
HtmlNodeCollection cells = row.SelectNodes("./td");
// Todo check for bounds of cells here
HtmlNode cell = cells[columnIndex];
int value = Int32.MinValue;
Int32.TryParse(cell.InnerText.Trim(), out value);
maxValue = Math.Max(value, maxValue);
}
e.WebTest.Context.Add(ContextParameterName, maxValue);
int FindColumnIndexByName(HtmlNodeCollection columns, string columnName)
{
for(int i=0; i<columns.Count; i++)
if (String.Equals(columns[i].InnerText, columnName, StringComparison.OrdinalIgnoreCase))
{
return i;
}
return -1;
}
Im writing SSAS MDX queries involving more than 2 axis' to retrieve a value. Using ADOMD.NET, I can get the returned cellset and determine the value by using
lblTotalGrossSales.Text = CellSet.Cells(0).Value
Is there a way I can get the CellSet's Cell(0) Value in my MDX query, instead of relying on the data returning to ADOMD.NET?
thanks!
Edit 1: - Based on Daryl's comment, here's some elaboration on what Im doing. My current query is using several axis', which is:
SELECT {[Term Date].[Date Calcs].[MTD]} ON 0,
{[Sale Date].[YQMD].[DAY].&[20121115]} ON 1,
{[Customer].[ID].[All].[A612Q4-35]} ON 2,
{[Measures].[Loss]} ON 3
FROM OUR_CUBE
If I run that query in Management Studio, I am told Results cannot be displayed for cellsets with more than two axes - which makes sense since.. you know.. there's more than 2 axes. However, if I use ADOMD.NET to run this query in-line, and read the returning value into an ADOMD.NET cellset, I can check the value at cell "0", giving me my value... which as I understand it (im a total noob at cubes) is the value sitting where all these values intersect.
So to answer your question Daryl, what I'd love to have is the ability to have the value here returned to me, not have to read in a cell set into the calling application. Why you may ask? Well.. ultimately I'd love to have one query that performs several multi-axis queries to return the values. Again.. Im VERY new to cubes and MDX, so it's possible Im going at this all wrong (Im a .NET developer by trade).
Simplify your query to return two axis;
SELECT {[Measures].[Loss]} ON 0, {[Term Date].[Date Calcs].[MTD] * [Sale Date].[YQMD].[DAY].&[20121115] * [Customer].[ID].[All].[A612Q4-35]} ON 1 FROM OUR_CUBE
and then try the following to access the cellset;
string connectionString = "Data Source=localhost;Catalog=AdventureWorksDW2012";
//Create a new string builder to store the results
System.Text.StringBuilder result = new System.Text.StringBuilder();
AdomdConnection conn = new AdomdConnection(connectionString);
//Connect to the local serverusing (AdomdConnection conn = new AdomdConnection("Data Source=localhost;"))
{
conn.Open();
//Create a command, using this connection
AdomdCommand cmd = conn.CreateCommand();
cmd.CommandText = #"SELECT { [Measures].[Unit Price] } ON COLUMNS , {[Product].[Color].[Color].MEMBERS-[Product].[Color].[]} * [Product].[Model Name].[Model Name]ON ROWS FROM [Adventure Works] ;";
//Execute the query, returning a cellset
CellSet cs = cmd.ExecuteCellSet();
//Output the column captions from the first axis//Note that this procedure assumes a single member exists per column.
result.Append("\t\t\t");
TupleCollection tuplesOnColumns = cs.Axes[0].Set.Tuples;
foreach (Microsoft.AnalysisServices.AdomdClient.Tuple column in tuplesOnColumns)
{
result.Append(column.Members[0].Caption + "\t");
}
result.AppendLine();
//Output the row captions from the second axis and cell data//Note that this procedure assumes a two-dimensional cellset
TupleCollection tuplesOnRows = cs.Axes[1].Set.Tuples;
for (int row = 0; row < tuplesOnRows.Count; row++)
{
for (int members = 0; members < tuplesOnRows[row].Members.Count; members++ )
{
result.Append(tuplesOnRows[row].Members[members].Caption + "\t");
}
for (int col = 0; col < tuplesOnColumns.Count; col++)
{
result.Append(cs.Cells[col, row].FormattedValue + "\t");
}
result.AppendLine();
}
conn.Close();
TextBox1.Text = result.ToString();
} // using connection
Source : Retrieving Data Using the CellSet
This is fine upto select on columns and on Rows. It will be helpful analyze how to traverse sub select queries from main query.
Given the following...
int maxResults = 25;
string code = "Thailand";
var q = from i in images where i.component_code == code select i;
var images = q.OrderByDescending(x => x.image_rating).Take(maxResults);
if (images.Count() > 0)
{
...
lblResult = string.Format("Viewing {0} Images Of A Possible {1}", images.Count(), ?);
}
How do I get the potential total number of images that would have been returned if Take() had not been used
Can't you use q.Count() for this?