#1233 SQuirreL hangs on lock in AWT-EventQueue

[Sergei]

SQuirreL hangs when user does certain operations.

Steps to reproduce:

1. Run long-running sql (select count() from largetable)
2. Go to current session properties
3. Change Maximum limit of SQL Result Tabs
4. Press OK

Expected result

1. SQuirreL shows working SQL Worksheet

Actual result

1. SQuirreL is not responding

JConsole shows that the thread AWT-EventQueue-1 is blocked by thread Thread-5 at SQLDatabaseMetaData.supportsCatalogsInTableDefinitions(), while thread Thread-5 is executing a SQL-query.

[Gerd Wagner]

Here is a citation of mails concerning this bug that can be found in our developers list:

Neville,

it's true that hangs occur if a JDBC connection is designed in a way that a running statement blocks any other access to a connection. If a JDBC driver is done that way there are several actions that can cause SQuirreL to hang while a statement is executing. Fortunately there seem to be only a few JDBC drivers behaving like that. In fact I only know of one.

A simple test to check this behaviour is to press the cancel button for a long running statement. If you get the message 'Failed to cancel statement. Perhaps the driver/RDDBMS does not support cancelling statements. ...' it is probable that your driver has this flaw.

Another way to get more information about hangs is to use the -detectEDT command line parameter. Here is an excerpt from our change log that describes how it works and what is does:

'New command line parameter:
Short form: -detectEDT
Long form: --detect-long-running-swing-edt-events
The parameter has no arguments.
The parameter enables SQuirreL to detect long running Swing Event Dispatch Thread events.
When the dispatch thread is blocked for longer than two seconds a warning containing a thread dump is written to the logs.'

Hope this helps

Gerd

Am 08.02.2016 um 07:58 schrieb Neville Rowe:

Hi, I was thinking a little bit about
https://sourceforge.net/p/squirrel-sql/bugs/1233/ and it chimes with
something I see occasionally. When working with a relatively large DB
server, SquirrelSQL can hang at times. I've never been able to get
anything repeatable so haven't raised a bug for it, however I think
it is certainly related to doing things whilst waiting for a query to
respond. For example clicking onto the objects tab whilst there is an
outstanding query and I am not using cached metadata. Or even writing
the next query whilst I'm waiting for a current query to respond -
specifically if the editor is looking up a column name for
auto-complete whilst the query results are just starting to be
returned. I believe the rules (recommendations) are to only have one
outstanding statement on a connection at any one time. And I suspect
metadata-lookups count as statements if the metadata isn't cached.
Can anyone remember how this is supposed to work in SquirrelSQL? If
not then I'm going to take a look at understanding and potentially
changing it. Probably try to move to having two connections per alias
so that metadata lookups go on a second connection, then do something
to ensure every statement on a connection is serialised. Thoughts?
Neville

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