I have a cql query I want to preform. The cql string looks like this:
SELECT * FROM :columnFamilyName WHERE <some_column_name> = :name AND <some_id> = :id;
My application has two layers of abstraction above the datastax driver. In one layer I want to bind the first two parameters and in another layer I'd like to bind the last parameter.
The problem is, if I bind the first two parameters, I get a BoundStatement to which I cannot bind another parameter. Am I missing something? Can it be done?
We're using datastax driver version 2.0.3.
Thanks,
Anatoly.
You should be able to bind any number of parameters to your BoundStatement using boundStatement.setXXXX(index,value) as follows :
BoundStatement statement = new BoundStatement(query);
statement.setString(0, "value");
statement.setInt(1, 1);
statement.setDate(2, new Date());
ResultSet results = session.execute(statement);
The problem though is that you're trying to use a dynamic column family whose value changes with the value you want to bind.
As far as I know, this is not allowed so you should instead prepare one statement per table and then use the right bound statement.
Related
The DataStax documentation says that to page through all data, the following CQL query is useful:
SELECT * FROM test WHERE token(k) > token(42);
Is it possible to build this query using the QueryBuilder? It provides a token method, but that seems to work only on column names, not on values.
Ideally, the value (in the example: 42) is of type Object, just like in the eq/gte/lte functions.
Try using automatic paging with the .fetchSize method. It uses token under the hood:
Automatic paging is introduced Cassandra 2.0. Automatic paging allows the developer to iterate on an entire ResultSet without having to care about its size: some extra rows are fetched as the client code iterate over the results while the old ones are dropped. The amount of rows that must be retrieved can be parameterized at query time. In the Java Driver this will looks like:
Statement stmt = new SimpleStatement("SELECT * FROM images");
stmt.setFetchSize(100);
ResultSet rs = session.execute(stmt);
Source: http://www.datastax.com/dev/blog/client-side-improvements-in-cassandra-2-0
QueryBuilder.fcall("token", value) ;
can solve the problem！
I am new to Cassandra and trying to write a program in C# for insertion and deletion.
I want to know if there is a way i can use variables instead of values in the insert command ?
When i try the following:
string s1="A";
string s2="B";
session.Execute("insert into users (lastname, firstname) values (s1,s2)");
The error occurs: A first chance exception of type 'Cassandra.SyntaxError' occurred in Cassandra.dll
Assuming that you are using the DataStax CQL3 C# Driver, the best way to go about this is to use a prepared statement. Once you set that up, you bind your variables and Execute, like this:
string strCQL = "INSERT INTO users (lastname, firstname) VALUES (?,?)";
string s1 = "A";
string s2 = "B";
PreparedStatement preparedStatement = session.Prepare(strCQL);
BoundStatement boundStatement = preparedStatement.Bind(s1,s2);
session.Execute(boundStatement);
Please don't ever build a CQL statement with string.Format (or string concatenation) and execute it. Cassandra/CQL can also be subject to injection-based attacks, so you should always use a prepared statement and bind your variables to it. Also, if you have a statement that you are going to run multiple times (ex: within a loop), you can get better performance by preparing it prior to the loop, and binding/executing within.
You need String.format or better yet use prepared statements.
http://www.datastax.com/documentation/developer/csharp-driver/2.1/csharp-driver/reference/21features/namedParameters.html
I'm facing some issues when trying to bind a list variable in an ArangoDB query. More concretely, the list might look like as follows and comes from a URL parameter in a certain Foxx controller endpoint:
.../someAPIEndpoint?list=A,B,C,D
I would like to be able to do something like this:
stmt = db._createStatement({query: "for i in [#list] return i"});
stmt.bind('list', req.params('list').split(','));
Since I do not know how many values will I receive from the API call, I can't create n bindings for each possible one. Is what I want to achieve even possible?
Thanks in advance.
you were almost there, you can bind an array directly to the parameter (i just removed "[" and "]" from your query:
stmt = db._createStatement({query: "for i in #list return i"});
stmt.bind('list', req.params('list').split(','));
I want to create a "prepared statement" in postgres using the node-postgres module. I want to create it without binding it to parameters because the binding will take place in a loop.
In the documentation i read :
query(object config, optional function callback) : Query
If _text_ and _name_ are provided within the config, the query will result in the creation of a prepared statement.
I tried
client.query({"name":"mystatement", "text":"select id from mytable where id=$1"});
but when I try passing only the text & name keys in the config object, I get an exception :
(translated) message is binding 0 parameters but the prepared statement expects 1
Is there something I am missing ? How do you create/prepare a statement without binding it to specific value in order to avoid re-preparing the statement in every step of a loop ?
I just found an answer on this issue by the author of node-postgres.
With node-postgres the first time you issue a named query it is
parsed, bound, and executed all at once. Every subsequent query issued
on the same connection with the same name will automatically skip the
"parse" step and only rebind and execute the already planned query.
Currently node-postgres does not support a way to create a named,
prepared query and not execute the query. This feature is supported
within libpq and the client/server protocol (used by the pure
javascript bindings), but I've not directly exposed it in the API. I
thought it would add complexity to the API without any real benefit.
Since named statements are bound to the client in which they are
created, if the client is disconnected and reconnected or a different
client is returned from the client pool, the named statement will no
longer work (it requires a re-parsing).
You can use pg-prepared for that:
var prep = require('pg-prepared')
// First prepare statement without binding parameters
var item = prep('select id from mytable where id=${id}')
// Then execute the query and bind parameters in loop
for (i in [1,2,3]) {
client.query(item({id: i}), function(err, result) {...})
}
Update: Reading your question again, here's what I believe you need to do. You need to pass a "value" array as well.
Just to clarify; where you would normally "prepare" your query, just prepare the object you pass to it, without the value array. Then where you would normally "execute" your query, set the value array in the object and pass it to the query. If it's the first time, the driver will do the actual prepare for you the first time around, and simple do binding and execution for the rest of the iteration.
I have a query where I need to do a "Where" clause for two different columns in two different tables but subsonic creates the same parametrized parameter name for both which is causing an issue. How can I fix this?
string _RawSql = new Select()
.From(Tables.Table1)
.InnerJoin(Tables.Table2)
.InnerJoin(Table3.SidColumn, Table2.Table3SidColumn)
.Where(Table1.SidColumn).IsEqualTo(2)
.And(Table3.SidColumn).IsEqualTo(1)
.BuildSqlStatement();
The query this is creating is
SELECT ....
FROM [dbo].[Table1]
INNER JOIN [dbo].[Table2] ON [dbo].[Table1].[Table2Sid] = [dbo].[Table2].[Sid]
INNER JOIN [dbo].[Table3] ON [dbo].[Table2].[Table3Sid] = [dbo].[Table3].[Sid]
WHERE [dbo].[Table1].[Sid] = #Sid
AND [dbo].[Table3].[Sid] = #Sid
Note that in the last two lines its using #Sid for both Table1 and Table3. How go I do it so it uses #Sid0 and #Sid1?
Any help would be appreciated. Thanks
Thanks for the response, I really appreciate it. I am using 2.1
I am already using TableColumn. Below is the c# subsonic code...
.Where(Table1.SidColumn).IsEqualTo(2)
.And(Table3.SidColumn).IsEqualTo(1)
which creates the following sql when viewed in sql profiler
WHERE [dbo].[Table1].[Sid] = #Sid
AND [dbo].[Table3].[Sid] = #Sid
Could you please show me how can I replace these lines with the way you are suggesting? I would really rather not use literal "Table2.Sid = 2"
ranmore, the issue is same with variables or with constants.
I have even tried
.Where("Table1.Sid").IsEqualTo(2)
.And("Table3.Sid").IsEqualTo(1)
This creates the query as
WHERE Table1.Sid = #Table1.Sid0
AND Table3.Sid = #Table3.Sid1
I finally get different parametrized vars in this case but now SQL Server complains because it does not like . in the parametrized var names.
I have no clue how to perform a join with 2 where clauses for 2 different tables!
What version are you using? In 2.2 You can use the TableColumn object to get around this (it may be the same for 2.1 as well. So instead of using the struct, as you're doing, you can use the object (Table2.SidColumn).
If push comes to shove - you can override everything with a string - so in your case you could use "Table1.Sid" and "Table2.Sid" right in the Where() method.
I haven't been able to confirm this, but perhaps the problem only happens with literals? (not sure if your sample code is like that for brevity's sake)
int table1SidColumnValue = 2;
int table3SidColumnValue = 1;
.Where(Table1.SidColumn).IsEqualTo(table1SidColumnValue)
.And(Table3.SidColumn).IsEqualTo(table2SidColumnValue)
I remember seeing a problem with this when using multiple .In() clauses with literal values, not sure if that applies to your problem though.
I'm not sure what version of the code I have but your query produces numbered parameters for me.
If you look at Line 255 of ANSISqlGenerator.cs
https://github.com/subsonic/SubSonic-2.0/blob/master/SubSonic/SqlQuery/SqlGenerators/ANSISqlGenerator.cs
c.ParameterName = String.Concat(col.ParameterName, query.Constraints.IndexOf(c));
The where parameters really should have numbers appended to them... maybe pull the latest version?