I'm trying to read PostgreSQL database with F#. The table I read contains column of hstore type but I'm not able to access this column.
I tried two approaches. First with using SqlDataProvider
type sql = SqlDataProvider<
ConnectionString = connString,
DatabaseVendor = Common.DatabaseProviderTypes.POSTGRESQL,
ResolutionPath = resPath,
IndividualsAmount = 1000,
UseOptionTypes = true, Owner="public">
let ctx = sql.GetDataContext()
for item in ctx.Public.Articles.Take(10) do printfn "%s" item.???
My item doesn't contain columns at all.
When I use another approach
type dbSchema =
SqlEntityConnection<
ConnectionString=connString,
Provider="Npgsql">
let ctx = dbSchema.GetDataContext()
for item in ctx.articles do printfn "%s" item.???
The item contains all columns except column of hstore type.
In the code of SqlProvider there I see some mapping of hstore in the PostgreSQL provider but I have no idea how to use it.
Related
I have a Vert.x web application that needs to query an AWS RDS instance running Postgres 10.7. The Vert.x JDBC client is io.vertx:vertx-jdbc-client:3.8.4. I want to query a table with the constraint that a certain column's value is included in a set of values:
select from table where column in/any (?)
I followed the Vertx documentation, which says to create a JsonArray and populate it with the values to inject into the query. The column is of type text and the list that I want to match on is a Java ArrayList<String>. My query code looks like:
String sql = "SELECT a FROM table WHERE col IN (?)";
List<String> values = someObject.someField();
sqlClient.getConnection(connectionResult -> {
if (connectionResult.failed()) {
// handle
} else {
SQLConnection connection = connectionResult.result();
JsonArray params = new JsonArray()
.add(values);
connection.queryWithParams(sql, params, queryResult -> {
if (queryResult.failed()) {
// handle
} else {
// parse
}
});
}
});
The query fails with the error: org.postgresql.util.PSQLException: Can't infer the SQL type to use for an instance of io.vertx.core.json.JsonArray. Use setObject() with an explicit Types value to specify the type to use.
I know that in the worst case, I can create a literal SQL string where col in (?, ?, ?, ..., ?) and add each String from the list to a JsonArray, but there must be a way to just add the ArrayList<String> as a parameter and keep the query simple. How can I specify a list of values to match against in my query?
The Vert.x JDBC Client does not support array parameters in queries.
However it is possible with the Vert.x Pg Client, which does not depend on JDBC. You need to modify your query first:
SELECT a FROM table WHERE col = ANY(?)
Then:
pgClient.preparedQuery(query, Tuple.of(possibleValues), collector, handler);
I'm trying to parse selected result from PostgreeSQL in Groovy, but something goes wrong, when I'm trying to parse it.
I used a lot of things, but I haven't reached the goal.
I've tried so:
I have three columns in postgre. One of the columns (document) is jsonb type and I want to parse it.
//instance of connection string to postrgre
PgAdmin pg = new
List<GroovyRowResult> result = pg.getSelectResult(Here goes select script)
for(Map oneRow in result) {
def document = oneRow.get("document")
println documnet //Well from here it works good, it prints jsonb data stored in document column.
def customerName = document.get("CustomerName") // it failes and goes on error, where CustomerName is inside jsonB.
}
I've also tried to use JsonSlurper, but it also fails.
In my CRUD Rest Service I do an insert into a DB and want to respond to the caller with the created new record. I am looking for a nice way to convert the map to json.
I am running on ballerina 0.991.0 and using a postgreSQL.
The return of the Update ("INSERT ...") is a map.
I tried with convert and stamp but i did not work for me.
import ballerinax/jdbc;
...
jdbc:Client certificateDB = new({
url: "jdbc:postgresql://localhost:5432/certificatedb",
username: "USER",
password: "PASS",
poolOptions: { maximumPoolSize: 5 },
dbOptions: { useSSL: false }
}); ...
var ret = certificateDB->update("INSERT INTO certificates(certificate, typ, scope_) VALUES (?, ?, ?)", certificate, typ, scope_);
// here is the data, it is map<anydata>
ret.generatedKeys
map should know which data type it is, right?
then it should be easy to convert it to json like this:
{"certificate":"{certificate:
"-----BEGIN
CERTIFICATE-----\nMIIFJjCCA...tox36A7HFmlYDQ1ozh+tLI=\n-----END
CERTIFICATE-----", typ: "mqttCertificate", scope_: "QARC", id_:
223}"}
Right now i do a foreach an build the json manually. Quite ugly. Maybe somebody has some tips to do this in a nice way.
It cannot be excluded that it is due to my lack of programming skills :-)
The return value of JDBC update remote function is sql:UpdateResult|error.
The sql:UpdateResult is a record with two fields. (Refer https://ballerina.io/learn/api-docs/ballerina/sql.html#UpdateResult)
UpdatedRowCount of type int- The number of rows which got affected/updated due to the given statement execution
generatedKeys of type map - This contains a map of auto generated column values due to the update operation (only if the corresponding table has auto generated columns). The data is given as key value pairs of column name and column value. So this map contains only the auto generated column values.
But your requirement is to get the entire row which is inserted by the given update function. It can’t be returned with the update operation if self. To get that you have to execute the jdbc select operation with the matching criteria. The select operation will return a table or an error. That table can be converted to a json easily using convert() function.
For example: Lets say the certificates table has a auto generated primary key column name ‘cert_id’. Then you can retrieve that id value using below code.
int generatedID = <int>updateRet.generatedKeys.CERT_ID;
Then use that generated id to query the data.
var ret = certificateDB->select(“SELECT certificate, typ, scope_ FROM certificates where id = ?”, (), generatedID);
json convertedJson = {};
if (ret is table<record {}>) {
var jsonConversionResult = json.convert(ret);
if (jsonConversionResult is json) {
convertedJson = jsonConversionResult;
}
}
Refer the example https://ballerina.io/learn/by-example/jdbc-client-crud-operations.html for more details.?
I am using EF Framework to retrieve the data from SQL DB.
Sub Request Table looks like below:
In this table "org_assigneddept" is foreign key to another Department Table.
I have list of Departments as Input and I want to retrieve only those rows from DB whose org_assigneddept is matching the list.
Please find my whole code:-
private List<EventRequestDetailsViewModel> GetSummaryAssignedDeptEventRequests(List<EmpRoleDeptViewModel> vmDept)
{
List<EventRequestDetailsViewModel> vmEventRequestDeptSummary = new List<EventRequestDetailsViewModel>();
RequestBLL getRequestBLL = new RequestBLL();
Guid subRequestStatusId = getRequestBLL.GetRequestStatusId("Open");
using (var ctxGetEventRequestSumm = new STREAM_EMPLOYEEDBEntities())
{
vmEventRequestDeptSummary = (from ers in ctxGetEventRequestSumm.SubRequests
where vmDept.Any(dep=>dep.DeptId == ers.org_assigneddept)
select new EventRequestDetailsViewModel
{
SubRequestId = ers.org_subreqid
}).ToList();
}
}
It is giving the following error at the LINQ Query level:-
System.NotSupportedException: 'Unable to create a constant value of
type 'Application.Business.DLL.EmpRoleDeptViewModel'. Only primitive
types or enumeration types are supported in this context.'
Please let me know as how can I achieve the result
You cannot pass the department VMs to SQL, it doesn't know what those are.
// Extract the IDs from the view models.. Now a list of primitive types..
var departmentIds = vmDept.Select(x => x.DeptId).ToList();
then in your select statement...
..
where departmentIds.Contains(id=> id == ers.org_assigneddept)
..
I'm using OLE and C#.NET to query the schema of a MS Access database. Specifically, I need to find out whether a particular column is an "identity" column or not. For SQL Server, I can use:
select COLUMNPROPERTY(object_id('dbo.tablename'),'columnname','IsIdentity')
... but when I invoke this SQL against Access, I get an OleDbException with the following message:
Undefined function 'COLUMNPROPERTY' in expression.
Searching the archives, it appears there are ways to do this with DAO, but I need to use OLE. Anyone happen to know how I can do this with OLE?
You can get the schema from the connection, for example:
cn.GetOleDbSchemaTable(OleDbSchemaGuid.Indexes,
new Object[] { null, null, null, null, "Table1" });
Is the indexes for Table1. One of the fields returned is PRIMARY_KEY
See http://msdn.microsoft.com/en-us/library/system.data.oledb.oledbschemaguid.columns(v=vs.71)
The same using the GetSchema method.
using(OleDbConnection con = new OleDbConnection(#"Provider=Microsoft.ACE.OLEDB.12.0;" +
"Data Source=C:\temp\db.mdb;" +
"Persist Security Info=False;"))
{
con.Open();
var schema = con.GetSchema("Indexes");
var col = schema.Select("TABLE_NAME = 'YourTableName' AND PRIMARY_KEY = True");
Console.WriteLine(col[0]["COLUMN_NAME"].ToString());
}