Master Detail with CachedUpdate

[AlexP]

Hello,

For a master table, the SequenceMode must be set to smInsert for correct master-detail data relation; for a detail table, you can use any value of SequenceMode, depending on the needed behaviour

[lauchuen]

but, does smInsert work on Offline mode ?

[AlexP]

Hello,

When using the Disconnected mode with enabled smlinsert, the server will be connected and the query for retrieving the sequence value will be sent automatically. After that, it will disconnect.

[lauchuen]

oic, i got it. but any draw back/disadvantage by using disconnected mode ?

[AlexP]

Hello,

The Disconnected mode is recommended to minimize data loss for networks with unstable/bad connection, where there are a lot of disconnections. In this mode, the connection is set only when data needs to be sent/received between a server and a client, therefore some performance loss is possible, as to perform each operation, a new connection is needed.

[lauchuen]

icic, thanks.

one more question, if the connection already establish (in good network environment), when performing operation, will it re-connect to server again ?

[AlexP]

hello,

If you work with a stable connection, you don't need to use the Disconnected mode. The main specificity of the Disconnected mode is that you don't need to open connection explicitly, i.e. you don't need to call the PgConnection.Connect method, the connection will be set on demand. If you connect to the server explicitly in the disconnect mode, than it will work in the usual mode without automatic server connection/disconnection.

[lauchuen]

hello,

its me again...now, i've another table schema which similar to previous.

Code: Select all

master table (
 id varchar(50) primary key,
 name varchar(50) NOT NULL,
);

detail table (
 id serial primary key,
 master_id varchar(50) NOT NULL,
 name varchar(50) NOT NULL
);

just the serial id field changed to varchar(50) and name now is not null. i found that master table must be posted before detail table insert record, is that true ? how to avoid that ?

following my settings:
tblMaster.SQL.Text := 'SELECT * FROM master';
tblMaster.CachedUpdates := True;
tblMaster.Options.DefaultValues := True;
tblMaster.Options.LocalMasterDetail := True;

tblDetails.SQL.Text := 'SELECT * FROM detail';
tblDetails.CachedUpdates := True;
tblDetails.Options.DefaultValues := True;
tblMaster.Options.LocalMasterDetail := True;

since name field now is not null, the users may insert detail record before fill the name field (since i can't control the users behavior), so any solution about this ? very urgent, please help.

[AlexP]

Hello,

For MasterDataSet it is necessary to use the smInsert mode, for DetailDataSet - any of modes, but to decrease server calls number and avoid counter increasing, it is better to use the smPost mode.

[lauchuen]

already use smInsert for MasterDataSet, but if i haven't Post the MasterDataSet before insert DetailDataSet record, after i Post the MasterDataSet, all DetailDataSet has gone (disappear).

and this only appear when the table was empty (no record), bugs?

[AlexP]

hello,

When realizing the Master-Detail relation, with any values of the CachedUpdates and LocalMasterDetail options, the Post method should be called for a master record before the detail records correspondent to it are added. But when enabling these options, the Post method will insert data only to the local DataSet without saving them to the server.

[lauchuen]

hi,

does the latest version have any update related to this features ?

[AlexP]

hello,

We are still working on this problem.
We will notify you as soon as we have any results.

[lauchuen]

thank you for the effort. since i think it is very important for database application development on the master-detail relationship. refer to the database side, there're also has a foreign key to control cascade or restrict update/delete. and i think there're also not every application use un-changeable ID for their application, hopeful your team can fix this problem soon.