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Hans J. Ellingsgaard

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Everything posted by Hans J. Ellingsgaard

  1. Hans J. Ellingsgaard

    Best Practices for FireDAC FetchMode/RecordCount Settings

    Is there anything that prevent you from indexing all the fields in the join and where clause? There is a good chance that it would give you a significiant boost on your query performance.
  2. Hans J. Ellingsgaard

    Best Practices for FireDAC FetchMode/RecordCount Settings

    If you make a select count query on an indexed field, it should only take a ms to execute. The resultset will only have one record. If your table only have 1500 records, the dataset.RecordCount should also respond quckly (not as quick as the record count thoug). There must be something else that goes wrong. What database are you using? Have you tried to run the queries directly in a db manager?
  3. Hans J. Ellingsgaard

    Best Practices for FireDAC FetchMode/RecordCount Settings

    A count(*) should always be done an an index field, or the point of using it is gone in the first place.
  4. Hans J. Ellingsgaard

    Best Practices for FireDAC FetchMode/RecordCount Settings

    To fetch all the records from a table to get the record count is in most cases a bad praxis. If it's a table with a lot of records, you will just put a lot unnessisary strain on the database server. A count(*) query, on the other hand, has a very limited impact on the server.
  5. Hans J. Ellingsgaard

    Best Practices for FireDAC FetchMode/RecordCount Settings

    You can use an extra query with a count(*) to get the number of records.
  6. Hans J. Ellingsgaard

    Admin Tool for IBToGo2020

    Have you tried IBExpert?
  7. Hans J. Ellingsgaard

    Analyze interbase slow queries

    You can analyze your queries in IBExpert, but you need the paid version to be able to see all the details.
  8. You will need a vpn connection between the datasnap server and the local network. SQL queries over an internet line is very slow, but if it's only a few records, maybe you can live with it. You would be better of writing some REST services to communicate between the two hosts.
  9. Hans J. Ellingsgaard

    What is the best way LoadFromFile & Thread? (FMX)

    I'm no expert in threads, but I'm shure that a LoadFromFile should be synchronized. As stated above the try/finally is pointless. If you only have these two commands in the thread, and both will be synchronized, there will be no point in putting them in a thread. It will probably just slow your program down.
  10. Hans J. Ellingsgaard

    InterBase or Firebird?

    Firebird is free. With Interbase you will have to pay for a license. I'm shure that both will serve you well, with RDBMS or as embedded.
  11. Hans J. Ellingsgaard

    Best way to refresh static data

    But you would get rid of all the trouble of sync‘ing the data, if you kept the data on the server. With a REST service you will probably be able to load the data much faster, and save a lot of bandwith - at least if you are on a slow network.
  12. MS SQL server can have deadlocks, just like any other database.
  13. You can minimize the deadlock problem, if you call starttransaction just before the ExecSQL, and call CommitTransaction right after ExecSQL. Then you also can make a controlled RollBack in case of an error.
  14. For Interbase the default username and password has been SYSDBA and masterkey, has it changed in later versions?
  15. Hans J. Ellingsgaard

    [Firedac] Connection Pooling

    Yes you'r right. I was thinking about a single user client with multiple datamodules.
  16. Hans J. Ellingsgaard

    [Firedac] Connection Pooling

    You could have just one FDConnection, and let all the other datamodules use that connection. You would then have just one place to set up all your connection logic, And by the way... Some SQL servers have licens restrictions on how many simultanious connections you can have, and if your are using one connection for each datamodule, you could easily end up being unable to connect to the SQL server.
  17. Hans J. Ellingsgaard

    TFDBatchMove delete records

    Why are you not using ApplyUpdates to delete the marked records from the database?
  18. Hans J. Ellingsgaard

    Refresh Current Record To Access Value Of Newly Inserted AutoInc Field

    If you can call the Generator directly, like in Interbase/Firebird and other db's, I would prefer that approach. I can't find any documentation that this is possible with Pervasive db's, but you can check it out. Create a query that calls the Generator and wrap it in a function like this. (The example is made in Interbase syntax). function GetGenID(GeneratorName: string): integer; begin with FDQGetGenID do begin SQL.Clear; SQL.ADD('SELECT GEN_ID ('+GeneratorName+', 1) from rdb$database'); Open; Result := Fields[0].AsInteger; Close; end; end; Then when you insert new data you will call the GetGenID function. FDQuery.insert; FDQueryID.Value:=GetGenID('GeneratorName'); FDQueryMASTERDATA.AsString:= 'Some value'; FDQuery.Post; You can also place the call to GetGenID in the FDQuery events, like OnNewRecord or BeforeInsert. --- If this approach is not possible with Pervasive, then this approach could work. It is at least working with Interbase. In this example I have used a DBGrid and A DataSource component to connect to the FDQuery. And the query has two fields called "ID" and "MASTERDATA". Set the AutoGenerator parameter value of ID field to arAutoInc (if you've not already done so). In the OnDataChange Event of the DataSource put the following code: if (FDQMasterID.Value < 0) and (FDQMaster.State in [dsInsert]) and not FDQMasterMASTERDATA.IsNull then begin FDQMaster.Post; FDQMaster.Refresh; end; You need to check if at least one of the fields has a value apart from the ID field, or you will get an error on the Post command, if the user adds to empty records.
  19. Hans J. Ellingsgaard

    FireDAC paramamania

    You need to close and open the query every time you change the parameter values, if it has a result set.
  20. Hans J. Ellingsgaard

    Copy Sqlite DB to tethered app

    You can use FDMemTables, they can load and save from streams, files and other datasets.
  21. Hans J. Ellingsgaard

    Best site/source for SQL Server questions?

    Yes, I can see that from your link. It came as a surprice to me, as I am mostly used to work with IB and Firebird databases. There is at NOLOCK isolationlevel, that will minimize risk of locking, but it will not be suitable, if there is a risk of data being changed during the execution of the query. Another thing to do is to make sure that all the fields in the where clause and the joins are indexed to avoid tablescans.
  22. Hans J. Ellingsgaard

    Best site/source for SQL Server questions?

    It sounds strange. You should never get a lock on a read only query. If you have many concurrent users, you could have drop of performance, but not locks.
  23. Hans J. Ellingsgaard

    Version Control System

    Bitbucket is a great versioning system based on git. You can have 5 users for free, so you can always give it a try. It works well with Sourcetree as a client. It,s also easy to integrate with Jira.
  24. Hans J. Ellingsgaard

    any suggestions on how to "lazy load" a BLOB/CLOB from Oracle DB?

    You can do it with two queries. Make one query that select's all the fields that you want in the grid (don't use "select *", use the wanted fieldnames instead). Then make another query with a parameter that select's the clob field for one record only. Like this: select [clob field] from [table name] where [Primary Field ID] = :ParameterName Then you open the second query after the first query has entered the wanted record. The parameter will get it's value from the first query. There might be an event on the grid you can use - I don't know the DevEx grid. You can also use the AfterScroll event of the dataset to open the second query. If you use the second approach, you will need to have a delay on the opening of the second query, or it will open after all scrolled records. You can use a timer to have a small delay. Disable it on the BeforeScroll event and enable it on the AfterScroll event. The delay should just be long enough to make shure that it is not triggering while the user is scrolling.
  25. Hans J. Ellingsgaard

    Delphi Tokyo - Is FDConnection manager broken ? - Need advice connecting MsSQL DB

    If your sql server is not on the same machine as your client, it might be that you don't have the right sql driver verison. Look into the ODBC Data Source Administrator for what version of sql driver you have. E.g for a SQL server 2008 you need at least a version 10.00. I'm not sure wich version you need for server 2012, but it is probably at bit higher than that. You can download the correct version from Microsoft.
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