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I'm using GreenDAO for database handling in Android. When performing many database changes (> 15.000) I get this error Message:

The connection pool for database '/data/data/...' has been unable to grant a connection to thread 312 (Thread-312) with flags 0x1 for 30.000002 seconds.

Everything gets stuck. Why does this error happen?

Ria
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Basic Coder
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  • Please provide more information on this issue. E.g. stack traces, does it occur on all tested devices?, Android versions tested, ... – Markus Junginger Aug 02 '12 at 12:30
  • I got the same problem. There are no stack trace, this same error repeatly appeared and I can no longer access the database. I wonder if somewhere in GreenDao there are open transaction but not end transaction in a finally clause. – Hiep Sep 07 '14 at 19:30

3 Answers3

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I got this message when I want to select a query on a table which is used on a transaction without ended transaction before. Problem solved after executing endTransaction() on finally block of transaction.

hkutluay
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    Also think about making batches when importing large datasets. Say, make `endTransaction()` and start a new transaction after n entities. – melbic Mar 30 '15 at 09:31
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I can't say for sure about this particular implementation, but there is a connectionpool usually backing a ORM. The connection pool opens a set number of connections to the database and recycles them as you close them and open new connections. What that error is telling you is that it probably hit a limit. That can happen for a large variety of reasons, one is that possibly there is some deadlock in the DB because you are updating two tables and two different transactions are holding different tables waiting for the other to release. Or simply that there are just too many open connections and the DB or connection pool just gets confused.

Sorry that is not really an answer, but you are going to need to look at the docs for GreenDAO to see how this might happen.

Kaediil
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    greenDAO does not use any connection pools itself. Apps with greenDAO behave just like many Android apps using SQLite. You get an SQLiteDatabase using some sort of SQLiteOpenHelper. Instances of DaoMaster/DaoSession refer to this SQLiteDatabase object. – Markus Junginger Aug 02 '12 at 12:28
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I got this message when creating too many connections to SQLite via DBFlow FlowQueryList . My solution was to make sure that once you were done with the query list to call endTransactionAndNotify() and then close() on the querylist.

Calling endTransactionAndNotify() alone did not do the trick. I hope this helps, this thread certainly helped me.

Blaze Gawlik
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