ZQuery and Refresh

[aebi]

Hello,

in Delphi 7 and Zeos 6.5.1 I often use "<ZQuery>.Refresh" to refresh the data displayed, for example in a DBGrid (Database is PostgreSQL 8.4).

After changing to Delphi XE 10, Zeos 7.14 and PostgreSQL 9.5, I have some problems doing this again.
Debugging leads to the unit "ZAbstractRODataset" -> "MoveRecNo"; the call of "Resync" (which belongs to "TDataSet") results in an access violation.
But : with some tables in the database, it works, with others not - all of them uses simple queries with only one table.

The client encoding for postgres dabase is set to "UTF-8".

Maybe some one has an idea about this ?

Thank You,
with best regards
Andreas

[marsupilami]

Hello aebi,

could you try what happens if yoiu use the current Zeos 7.2 Beta? It has lots of improvements and should already be more stable than Zeos 7.1. Please get it via SVN from http://svn.code.sf.net/p/zeoslib/code-0 ... esting-7.2.

If the error persists, it helps very much to have a sample program that triggers the error.

With best regards,

Jan

[aebi]

Hello Jan,

I just checked out 7.2 and will do some test.

Thank You,
best regards
Andreas

[seiraya]

Hi,

I do have same problem TZQuery.Refresh, it produce access violation.
I Use 7.1.4-stable, XE7 with MySQL

Regards

[marsupilami]

Hello seiraya,

could you please try using the current Zeos 7.2 version from SVN? We will (soon) release this one as the stable version. It has a lot of bugfixes, speed improvements and also new features.
With best regards,

Jan

[aebi]

Hello again,
and the best wishes for the new year !

some time ago, I posted about the problem with "refresh"; meanwhile I had the chance to test again, therefore I checked out the version 7.2 (SVN revision 3892).

First : the problem seems to be the same (unit ZDatasetUtils, "FetchFromResultSet", "Current.DataType" is "ftWideString"; I'm using Delphi XE 10, Windows 10 (64 bit) and Postgresql 9.6).

Second : "TZPostgreSQLConnection.SetTransactionIsolation" (in unit ZDbcPostgreSql) seems to have an error : the syntax for "SET SESSION CHARACTERISTICS AS TRANSACTION" must have "ISOLATION LEVEL", not just only "ISOLATION" (SQL-Syntax for Postgresql - at least in version 9.6).
Should I post this also in the 7.2 - forum ?

with best regards
Andreas

[aebi]

Hello (again...),
maybe it's helpfull : the query with the refresh-problem has an "AfterOpen"-Event, this event changes display-labels, adds "OnGetText"-Events to some fields and - this is some how the problem - changes the index (FieldByName ('XY').Index := n).
Without changing the index, the refresh is no problem.
With channging less then (in my special case) five indexes, the refresh is also no problem.
With changing more then five indexes, there is the problem with the access violation.

with best regards
Andreas

[marsupilami]

Hello Andreas,

I will look into the PostgreSQL problem. It seems, I introduced that bug...

Regarding the refresh problem - could you prepare a small example project, maybe including a small database or the script for the database? That would make debugging this issue a lot more easy.

With best regards,

Jan

[aebi]

Hello Jan,

I could reduce the problem to the following :

- (with SQL) : "create table refreshdata (no Integer, info_data Char (50))"
- (with SQL) : "insert into refreshdata values (1, 'info 1')"

- create a delphi project with ZConnection to the database and ZQuery
- ZQuery.SQL.Text := 'SELECT * FROM refreshdata ORDER BY no'
- ZQuery.AfterOpen := MyAfterOpen;
- MyAfterOpen (DataSet: TDataSet) with "ZQuery.FieldByName ('info_data').Index := 0;"
- ZQuery.Open;

--> "ZQuery.Refresh;" (I used a button-click to trigger) generates the acess violation.
This is in function "SysReallocMem", the last Zeos-procedure is "ZDbcCache.TZRowAccessor.SetUnicodeString(1, 'info 1')"

My Environment : Windows 10 (64 Bit); Delphi XE 10, Zeos 7.14, Postgres 9.6 (32 Bit).

I also tested Zeos 7.2 (see post before) and also Postgres 9.4 / 9.5 (32 Bit).

The application is compiled as 32-Bit-Application.


with best regards
Andreas

[marsupilami]

Hello Andreas,

thank you. I will try to reproduce the bug.
Regards,

Jan

[marsupilami]

Hello Andreas,

fixing this bug seems to be harder than I thought. Just wanted to let you know, it is not forgotten.
Best regards,

Jan

[aebi]

Thank You, Jan !

For the moment (in that case) I can do "<Query>.Close", then "<Query>.Open", but if Refresh will work, it would by fine.

with best regards
Andreas

[marsupilami]

Hello Andreas,

the problem has been fixed im the current SVN revision of Zeos 7.2.
With best regards,

Jan

[aebi]

Ok, thank You, Jan, I will check out (probably the next days) and try it.

with best regards
Andreas