Develop Reference

How to store and then execute linq2db query?

I'm very new to C#. In other languages I'm used to work with DB in a way "prepare, then execute statement with needed parameters", so I could pass prepared query to function and do all such things.
Now I'm trying to solve this task: get almost identicaly result sets from different databases in different contexts. Like you have "files" table with files metadata and in one DB it does have "file_priority" field, and in other DB it does have "file_description" field and so on, but most fields are common and processing logic are almost same.
So I wanted to prepare query in outer code and pass it along with needed param values to data-processing function (or class).
I can't find any example of executing (pass param values to query) linq2db query.
==========UPD============
Ok, example. Let's talk about Perl.
package main1;
use FileProcessor;
my $sth = $dbh->prepare(qq[ SELECT name, extension, file_priority FROM files WHERE file_id = ? ]);
my $processor = new FileProcessor(query => $sth);
my $file_id = $ENV{file_id};
my $file_data = $processor->get_file(id => $file_id);
package main2;
use FileProcessor;
my $sth = $dbh->prepare(qq[ SELECT name, extension, file_description FROM files WHERE file_id = ? ]); # preparing query
my $processor = new FileProcessor(query => $sth);
my $file_id = $ENV{file_id};
my $file_data = $processor->get_file(id => $file_id);
package FileProcessor;
sub new {
my $class = shift;
my $self = {#_};
bless $self, $class;
}
sub get_file {
my $self = shift;
my %params = #_;
$self->{query}->execute($params{$file_id}); #passing params to query
my $file_data = $self->{query}->fetchrow_hashref; # fetching result from DB
# do something with file data
# ...
return $file_data;
}

linq2db will not give you preparation step. But you can run raw query via a lot of extensions:
db.Query<File>("SELECT name, extension, file_priority FROM files WHERE file_id = #fileid",
new DataPamater("#fileid", id));
db.Query<File>("SELECT name, extension, file_priority FROM files WHERE file_id = #fileid",
new { fileid = id });
It is not typical for linq2db to do that in such way, because it supports LINQ queries and parameters will be created automatically:
var id = 1;
var query =
from f in db.GetTable<File>()
where f.file_id = id
select new File
{
name = f.name,
extension = f.extension,
file_priority = f.file_priority
};
var file = query.FirstOrDefault();

Must declare the scalar variable - Dapper

I do multiple mapping on the dapper. Then I try to implement dapper builder
But the it return exception:
Must declare the scalar variable \"#ExecutionId\".\r\nInvalid usage of the option NEXT in the FETCH statement.
Without multiple mapping, never give a problem
Here my snippet code
var Builder = new SqlBuilder();
var SelectedQuery = Builder.AddTemplate(# "SELECT e.[Id], e.[BuyOrderBookId], e.[SellOrderBookId], e.[Volume], e.[Price], e.[CreationDate], e.[StatusId], bo.[UserId], bo.[MarketId], so.[UserId] FROM[dbo].[Execution] AS e JOIN[dbo].[OrderBook] AS bo ON e.BuyOrderBookId = bo.Id JOIN[dbo].[OrderBook] as so ON e.SellOrderBookId = so.Id
/**where**/
ORDER BY e.[CreationDate] DESC OFFSET #skip ROWS FETCH NEXT #take ROWS ONLY;
");
//Execution ID
if (filter.ExecutionId.HasValue)
Builder.Where("e.[Id] = #ExecutionId", new {ExecutionId = filter.ExecutionId.Value
});
var query = await connection.QueryAsync < ExecutionViewModel, OrderBookViewModel, OrderBookViewModel, ExecutionViewModel > (SelectedQuery.RawSql, (execute, buyOrder, sellOrder) => {
execute.BuyUserId = buyOrder.UserId;
execute.SellUserId = sellOrder.UserId;
execute.MarketId = buyOrder.MarketId;
return execute;
},
splitOn: "UserId,UserId",
param: new {
SelectedQuery.Parameters,
skip = (pagingParam.PageNumber - 1) * pagingParam.PageSize,
take = pagingParam.PageSize
});
Anyone know did I do something wrong here?
Update
I just fix like this
if (filter.ExecutionId.HasValue)
Builder.Where(String.Format("e.[Id] = {0}",filter.ExecutionId));
I believe this is not good way to implement. Is risk sql injection.

Try changing the where clause like this:
if (filter.ExecutionId.HasValue)
Builder.Where("e.[Id]", new {Id = filter.ExecutionId.Value});

You can add parameters like this.
if (filter.ExecutionId.HasValue)
{
Builder.Where("e.[Id] = #ExecutionId");
((DynamicParameters)SelectedQuery.Parameters)
.AddDynamicParams(new {
ExecutionId = filter.ExecutionId.Value
});
}

Getting more than 100 documents back from ExecuteStoredProcedureAsync

I have a CosmosDB instance that is using the SQL / DocumentDB interface. I am accessing it via the .NET SDK.
I have the stored procedure that I call with ExecuteStoredProcedureAsync. But I can only get a max of 100 documents back. I know this is the default option. Can I change it?
The optional parameter to ExecuteStoredProcedureAsync is a RequestOptions object. The RequestOptions doesn't have properties for MaxItemCount or continuation tokens.

You need to change the SP itself to adjust the amount of records you'd like to return. Here is a complete example with the implemented skip/take logic in SP-
function storedProcedure(continuationToken, take){
var filterQuery = "SELECT * FROM ...";
var accept = __.queryDocuments(__.getSelfLink(), filterQuery, {pageSize: take, continuation: continuationToken},
function (err, documents, responseOptions) {
if (err) throw new Error("Error" + err.message);
__.response.setBody({
result: documents,
continuation: responseOptions.continuation
});
});
}
Here is a corresponding C# code:
string continuationToken = null;
int pageSize = 500;
do
{
var r = await client.ExecuteStoredProcedureAsync<dynamic>(
UriFactory.CreateStoredProcedureUri(DatabaseId, CollectionId, "SP_NAME"),
new RequestOptions { PartitionKey = new PartitionKey("...") },
continuationToken, pageSize);
var documents = r.Response.result;
// processing documents ...
// 'dynamic' could be easily substituted with a class that will cater your needs
continuationToken = r.Response.continuation;
}
while (!string.IsNullOrEmpty(continuationToken));
As you can see, there is a parameter that controls the number of records to send back - pageSize. As you've noticed, pageSize is 100 by default. In case you need to return all at once, specify -1.

The RequestOptions doesn't have properties for MaxItemCount or
continuation tokens.
MaxItemCount is a parameter in Feedoptions.
ExecuteStoredProcedureAsync method does not limit the returned data entries, the key is your query operation in the Stored Procedure set the maximum number of entries you want to return.
Please refer to the sample stored procedure code as below :
function sample(prefix) {
var collection = getContext().getCollection();
var isAccepted = collection.queryDocuments(
collection.getSelfLink(),
'SELECT * FROM root r',
{ pageSize: 1000 },
function (err, feed, options) {
if (err) throw err;
if (!feed || !feed.length) {
var response = getContext().getResponse();
response.setBody('no docs found');
}
else {
var response = getContext().getResponse();
var body = "";
for(var i=0 ; i<feed.length;i++){
body +="{"+feed[i].id+"}";
}
response.setBody(JSON.stringify(body));
}
});
if (!isAccepted) throw new Error('The query was not accepted by the server.');
}
Result :

Executing ST_WITHIN using stored procedure in documentdb

I am trying to get a count for my location inside a polygon. Here is my stored proc:
function count(poly) {
var collection = getContext().getCollection();
var query = {query: 'Select f.id from f WHERE ST_WITHIN(f.location, #poly)',
parameters: [{name: '#poly', value: poly}]};
var isAccepted = collection.queryDocuments(
collection.getSelfLink(),
query,
function (err, docs, options) {
if (err) throw err;
if (!docs || !docs.length) getContext().getResponse().setBody('no docs found');
else getContext().getResponse().setBody(docs.length);
});
if (!isAccepted) throw new Error('The query was not accepted by the server.');}
When I execute the same query in query explorer, I get the results, but through stored procedures, its returning "no docs found". It is returning the results for simpler queries but for that too, the max count returned is always 100. Not sure what am I doing wrong.
Thanks in advance.
P.S.: I tried using ST_DISTANCE for these coordinates. It did returned count as 100(max value), but is not at all working for ST_WITHIN.
Edit:
It was not working.So I tried this as described in the official example for counting the results. And voila!! It worked. So I moved to the next step to count all the locations in all the polygons I had as locally, there were too many round trips to get the count for each polygon. But calling the same function from a loop does'nt return anything. I have already tested each query of the array in documentdb studio and it does return results. Please help!!! The code for new procedure is:
function countABC(filterQueryArray) {
var results = [];
for (i = 0; i < filterQueryArray.length; i++) {
countnew(filterQueryArray[i].QueryString, "");
}
getContext().getResponse().setBody(results);
function countnew(filterQuery, continuationToken) {
var collection = getContext().getCollection();
var maxResult = 50000;
var result = 0;
tryQuery(continuationToken);
function tryQuery(nextContinuationToken) {
var responseOptions = {
continuation: nextContinuationToken,
pageSize: maxResult
};
if (result >= maxResult || !query(responseOptions)) {
setBody(nextContinuationToken);
}
}
function query(responseOptions) {
return (filterQuery && filterQuery.length) ?
collection.queryDocuments(collection.getSelfLink(), filterQuery, responseOptions, onReadDocuments) :
collection.readDocuments(collection.getSelfLink(), responseOptions, onReadDocuments);
}
function onReadDocuments(err, docFeed, responseOptions) {
if (err) {
throw 'Error while reading document: ' + err;
}
result += docFeed.length;
if (responseOptions.continuation) {
tryQuery(responseOptions.continuation);
} else {
setBody(null);
}
}
function setBody(continuationToken) {
var body = {
count: result,
continuationToken: continuationToken
};
results.push(body);
}
}
}

With new sproc, it's not helpful to set result after the loop because at that time no queries are executed (results array will be empty). The idea is that all CRUD/query calls are queued and are executed after the script that queued them is finished (in this case main script).
Setting result/body needs to be done from callback. This is partially done already, but there is an issue that for every call of countnew, the "result" variable is reset to 0. Essentially, "var result = 0" needs to be done in main script.
Also, it's not recommended to use loops like the "for" loop when it calls CRUD/queries in a loop without waiting for previous CRUD/query to finish (due to async nature), otherwise checking for isAccepted is not reliable. What's recommended it to serialize this loop, something like this:
var result = 0;
step();
function step() {
if (filterQueryArray.length == 0) setBody(null);
else {
var query = filterQueryArray.shift();
// process current query. In the end (from callback), call step() again.
}
}
Does this make sense?

Azure Mobile Services - Passing arrays through Custom Parameters

I'm using Azure Mobile Services with a C# client. I have a table of "Scores" that have a Facebook Id for each score. What I need to do is pass in an array of friends for a user and return all scores in that list of friends.
So I tried this on the client:
return _client.GetTable<Score>().WithParameters(new Dictionary<string, string>
{
{ "Level", level.ToString() },
//aggregate our string[] to a comma-delimited string
{ "Friends", friends.Aggregate(new StringBuilder(), (b, s) => b.Append(s).Append(',')).ToString() }
}).ToListAsync();
Which is weird I only have the option to pass in strings for custom parameters.
So I did this on the server's read:
function read(query, user, request) {
query.where({ Level: request.parameters.Level, UserId: request.parameters.Friends.split(',') });
request.execute();
}
It doesn't seem like a comma-delimited list is going to work. I get this error on the server:
Error in script '/table/Score.read.js'. Error: Unsupported literal value chucknorris,bobloblaw,
NOTE: I passed chucknorris and bobloblaw as Facebook ids for a test.
Is there another way to make this work? The "Level" value filters just fine if I take out the string delimited stuff.

Your usage of the mssql object definitely works, but you can also use a function in the query.where call, with the function returning the condition you want:
function read(query, user, request) {
query.where(function(level, userIds) {
return this.Level === level && this.UserId in userIds;
}, request.parameters.Level, request.parameters.Friends.split(','));
request.execute();
}
Notice that the in operator in this function doesn't behave quite exactly like the in operator in JavaScript. Instead, it's used exactly to have an 'or' grouping of equality statements, which you were creating "by hand" to pass to the SQL object.

Got it working with this server-side script:
function read(query, user, request) {
var innerSql = '';
var friends = request.parameters.Friends.split(',');
var parameters = new Array(friends.length + 1);
parameters[0] = request.parameters.Level;
for (var i = 0; i < friends.length; i++) {
if (i !== 0) {
innerSql += ' or ';
}
innerSql += 'UserId = ?';
parameters[i + 1] = friends[i];
}
mssql.query('select * from Score where Level=? and (' + innerSql + ')', parameters, {
success: function (results) {
request.respond(statusCodes.OK, results);
}
});
}
I'll keep this answer open for a few days if someone has a cleaner solution.