Project ... raised exception class 'External:SIGSEGV
lazarus / 16-Databases

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kStarbe · 2016-07-16 09:46

I wanted to display a MySQL query result in a grid. So I added the
following components:
MySQL56Connection
SQLTransaction
SQLQuery
DataSource
DBGRid.

Then linking the objects together I select
SQLTransaction.database to MySQL56Connection
SQLQuery.Database to MySQL56Connection
SQLQuery.Transaction to SQLTransaction
SQLQuery.Datasource to Datasource (!)
Datasource.Dataset to SQLQuery
Datagrid.Datasource to Datasource.

Run the app, saw the data but as soon as I try to move the record, I
got the above message.

After lots of searches, I did look at the whole chain and noticed
there was a circular reference between the Datasource and the
SQLquery.

Fun is that if you first set the link between SQL and Source from the
Source fisrt, then you cannot set it on top from the SQL side. This
warns you that a circular reference is there.
In the ohter direction, first set the datasource in the SQL and then
the SQL in the datasource then no error but the SIGSEGV.

So there should be a similar check in both components.

I hope this can save you some time.

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tomsi42 · 2018-03-01 10:09

Thanks for the tip.

I got into exactly this situation when I was working with the SqlDb
tutorial yesterday.

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MPO · 2019-04-08 10:50

Thank you for the solution.

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cappe · 2019-04-08 14:37

Thank you