Hi,
I think the problem is not the database, but how you use the JDBC API. If
you share a connection and run this in parallel, then the following
sequence may occur:
insertTree executeUpdate
insertTree executeUpdate
keys = insertTree.getGeneratedKeys
keys = insertTree.getGeneratedKeys
keys.next
keys.next
This is not what you want.
Regards,
Thomas
On Tuesday, March 18, 2014, <[email protected]> wrote:
> If sharing a connection across multiple threads, I sometimes get a "No
> data is available [2000-175]" if returning a generated key. The same code
> runs fine if I use one connection per thread.
>
> *Question:* Is it known and accepted behavior, that connections may not
> be used concurrently from separate threads?
>
> - If yes, it would be good to state this in the h2 documentation,
> since the topic arises from time to time, see for example
>
> https://groups.google.com/forum/#!searchin/h2-database/identity$20concurrency/h2-database/za6Ox1mrFIU/P_ZZm59ZiaMJ
> - If no, this can be considered a bug report.
>
> To reproduce, execute the following scala app:
>
>
> object H2BugReport extends App {
>
> import java.sql._
> import scala.concurrent.ExecutionContext.Implicits.global
> import scala.concurrent.Future
>
> Class forName "org.h2.Driver"
> val url = "jdbc:h2:mem:"
> val connection = DriverManager getConnection (url, "sa", "")
>
> connection.createStatement execute """
> CREATE SEQUENCE treeEntriesIdSeq;
> CREATE TABLE TreeEntries (
> id BIGINT DEFAULT (NEXT VALUE FOR treeEntriesIdSeq) PRIMARY KEY,
> name VARCHAR(256) NOT NULL
> );
> CREATE TABLE DataEntries (
> id BIGINT PRIMARY KEY,
> name VARCHAR(256) NOT NULL
> );
> """
>
> val insertTree = connection prepareStatement (
> "INSERT INTO TreeEntries (name) VALUES (?);",
> Statement.RETURN_GENERATED_KEYS
> )
>
> val insertData = connection prepareStatement (
> "INSERT INTO DataEntries (id, name) VALUES (?, ?);"
> )
>
> Future { // comment out this block, and the other block executes fine
> (1 to 50) foreach { n =>
> insertData setLong (1, n)
> insertData setString (2, s"$n")
> insertData executeUpdate
> }
> }
>
> (1 to 50) foreach { n =>
> println(s"inserting $n in tree")
> insertTree setString (1, s"$n")
> insertTree executeUpdate
> val keys = insertTree.getGeneratedKeys
> keys.next
> keys.getLong(1)
> }
> }
>
>
> This will yield:
>
>
> inserting 1 in tree
> Exception in thread "main" org.h2.jdbc.JdbcSQLException: Keine Daten
> verfügbar
> No data is available [2000-175]
> at org.h2.message.DbException.getJdbcSQLException(DbException.java:332)
> at org.h2.message.DbException.get(DbException.java:172)
> at org.h2.message.DbException.get(DbException.java:149)
> at org.h2.message.DbException.get(DbException.java:138)
> at org.h2.jdbc.JdbcResultSet.checkOnValidRow(JdbcResultSet.java:3111)
> at org.h2.jdbc.JdbcResultSet.get(JdbcResultSet.java:3117)
> at org.h2.jdbc.JdbcResultSet.getLong(JdbcResultSet.java:637)
> at
> bugreport.h2.H2BugReport$$anonfun$2.apply$mcJI$sp(H2BugReport.scala:48)
>
>
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