[ http://issues.apache.org/jira/browse/DERBY-1706?page=all ]
Mamta A. Satoor updated DERBY-1706:
-----------------------------------
Attachment: DERBY1706NPEwithSessionSchemaV1diff.txt
I have attached a patch(DERBY1706NPEwithSessionSchemaV1diff.txt) to this Jira
entry to fix the null pointer exception problem. But before going into the
details of the patch, I want to provide some background information about
SESSION schema and global temporary tables.
SESSION schema is a special schema which is used for global temporary tables.
In order to handle global temporary table, Derby creates a in-memory SESSION
schema descriptor which does not have any uuid associated with it. A physical
SESSION schema(with it's uuid set properly) will be created *only* if there is
a persistent object created in it by a user. Global temporary tables can only
reside in SESSION schema and Derby documentation recommends that SESSION schema
should not be used for other persistent objects. This is because the same
object name could be referencing different objects within SESSION schema
depending on in what order they got created.
For instance
create table session.t1(c11 int);
-- the following select will get data from the persistent table t1 in SESSION
schema
select * from session.t1;
declare global temporary table session.t1(c11 int, c12 int) on commit delete
rows not logged;
-- the following select this time will return data from the temporary table t1
rather than persistent table t1
-- This is because, at any time, if there is a global temporary table by the
table referenced by a statement,
-- then Derby will always pick up the global temporary table. If no global
temporary table by that name is
-- found, then Derby will look for persistent table in SESSION schema. If none
found, then error will be thrown
select * from session.t1;
-- following will drop the temporary table t1 and not the persistent table t1
drop table session.t1;
-- the following select will get data from the persistent table t1 in SESSION
schema because temporary table
-- doesn't exist anymore
select * from session.t1;
So, as can be seen from the example above, the statements referencing SESSION
schema objects could have different meanings depending on what kind of objects
exist in SESSION schema. Because of this, the compiled plans of statements
referencing SESSION schema are not saved in the statement cache, rather they
get compiled everytime they are executed. In order to enforce this, in the
compilation phase, Derby checks if the statement at hand is referencing a
SESSION schema object by calling referencesSessionSchema method. If this method
returns true, the statement's compiled plan will not be saved in the statement
cache.
Now, taking the script provided by Yip which results in NPE
set schema session;
create table t1 (i int);
Derby calls referencesSessionSchema while compiling "create table t1 (i int); "
to see if it references SESSION schema object. Since, there is no schema
associated with the table t1, Derby will check for the compilation schema which
in this case is SESSION schema because we used "set schema session; ". (This
happens in QueryTreeNode.getSchemaDescriptor(String schemaName, boolean
raiseError) line 1486). The method
then tries to call an equal method on the UUID associated with the SESSION
schema descriptor but since it is null(because no physical SESSION schema has
been created yet), we end up with a null pointer exception. This will happen
only if no physical SESSION schema has been created yet and user tries to
create a first persistent object inside SESSION schema after doing a set schema
session.
Following will not give a NPE because user hand created SESSION schema before
doing set schema SESSION and creating an object inside it.
create schema session;
set schema session;
create table t1 (i int);
The hand creation of SESSION schema causes Derby to have a schema descriptor
for SESSION schema with it's uuid set correctly.
The fix for the NPE is simple and that is to check if the UUID is null. I have
added test to existing lang/declareGlobalTempTableJava and ran derbyall on
Windows XP with Sun jdk 1.4 and everything ran fine.
The svn stat -q o/p is as follows
M java\engine\org\apache\derby\impl\sql\compile\QueryTreeNode.java
M
java\testing\org\apache\derbyTesting\functionTests\tests\lang\declareGlobalTempTableJava.java
M
java\testing\org\apache\derbyTesting\functionTests\master\declareGlobalTempTableJava.out
Please let me know if anyone has any comments.
> NullPointerException occurs when trying to create a table in schema SESSION
> ---------------------------------------------------------------------------
>
> Key: DERBY-1706
> URL: http://issues.apache.org/jira/browse/DERBY-1706
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.2.1.0
> Environment: Sun JDK 1.4.2
> Reporter: Yip Ng
> Assigned To: Mamta A. Satoor
> Priority: Minor
> Attachments: DERBY1706NPEwithSessionSchemaV1diff.txt
>
>
> NPE occurs when attempting to create a table in schema session:
> ij version 10.2
> ij> connect 'jdbc:derby:wombat;create=true' user 'user1';
> WARNING 01J14: SQL authorization is being used without first enabling
> authentica
> tion.
> ij> set schema session;
> 0 rows inserted/updated/deleted
> ij> create table t1 (i int);
> ERROR XJ001: Java exception: ': java.lang.NullPointerException'.
> derby.log:
> ----------------------------------------------------------------
> 2006-08-16 20:49:02.765 GMT:
> Booting Derby version The Apache Software Foundation - Apache Derby -
> 10.2.1.0 beta - (430903): instance c013800d-010d-18be-88cf-00000013f010
> on database directory C:\work3\derby\tests\derby-10.2.1.0\lib\wombat
> Database Class Loader started - derby.database.classpath=''
> 2006-08-16 20:49:17.312 GMT Thread[main,5,main] (XID = 122), (SESSIONID = 0),
> (DATABASE = wombat), (DRDAID = null), Cleanup action starting
> 2006-08-16 20:49:17.312 GMT Thread[main,5,main] (XID = 122), (SESSIONID = 0),
> (DATABASE = wombat), (DRDAID = null), Failed Statement is: create table t1 (i
> int)
> java.lang.NullPointerException
> at
> org.apache.derby.impl.sql.compile.QueryTreeNode.getSchemaDescriptor(Unknown
> Source)
> at
> org.apache.derby.impl.sql.compile.DDLStatementNode.getSchemaDescriptor(Unknown
> Source)
> at
> org.apache.derby.impl.sql.compile.DDLStatementNode.getSchemaDescriptor(Unknown
> Source)
> at
> org.apache.derby.impl.sql.compile.CreateTableNode.referencesSessionSchema(Unknown
> Source)
> at
> org.apache.derby.impl.sql.GenericPreparedStatement.referencesSessionSchema(Unknown
> Source)
> at org.apache.derby.impl.sql.GenericStatement.prepMinion(Unknown Source)
> at org.apache.derby.impl.sql.GenericStatement.prepare(Unknown Source)
> at
> org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.prepareInternalStatement(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedStatement.execute(Unknown Source)
> at org.apache.derby.impl.jdbc.EmbedStatement.execute(Unknown Source)
> at org.apache.derby.impl.tools.ij.ij.executeImmediate(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.doCatch(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.runScriptGuts(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.go(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main.go(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main.mainCore(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main14.main(Unknown Source)
> at org.apache.derby.tools.ij.main(Unknown Source)
> Cleanup action completed
> 2006-08-16 20:49:55.312 GMT:
> Shutting down instance c013800d-010d-18be-88cf-00000013f010
> ----------------------------------------------------------------
> sysinfo:
> ------------------ Java Information ------------------
> Java Version: 1.4.2_12
> Java Vendor: Sun Microsystems Inc.
> Java home: C:\Program Files\Java\j2re1.4.2_12
> Java classpath: derby.jar;derbytools.jar;.
> OS name: Windows XP
> OS architecture: x86
> OS version: 5.1
> Java user name: Yip
> Java user home: C:\Documents and Settings\Yip
> Java user dir: C:\work3\derby\tests\derby-10.2.1.0\lib
> java.specification.name: Java Platform API Specification
> java.specification.version: 1.4
> --------- Derby Information --------
> JRE - JDBC: J2SE 1.4.2 - JDBC 3.0
> [C:\work3\derby\tests\derby-10.2.1.0\lib\derby.jar] 10.2.1.0 beta - (430903)
> [C:\work3\derby\tests\derby-10.2.1.0\lib\derbytools.jar] 10.2.1.0 beta -
> (430903
> )
> ------------------------------------------------------
> ----------------- Locale Information -----------------
> Current Locale : [English/United States [en_US]]
> Found support for locale: [de_DE]
> version: 10.2.1.0 - (430903)
> Found support for locale: [es]
> version: 10.2.1.0 - (430903)
> Found support for locale: [fr]
> version: 10.2.1.0 - (430903)
> Found support for locale: [it]
> version: 10.2.1.0 - (430903)
> Found support for locale: [ja_JP]
> version: 10.2.1.0 - (430903)
> Found support for locale: [ko_KR]
> version: 10.2.1.0 - (430903)
> Found support for locale: [pt_BR]
> version: 10.2.1.0 - (430903)
> Found support for locale: [zh_CN]
> version: 10.2.1.0 - (430903)
> Found support for locale: [zh_TW]
> version: 10.2.1.0 - (430903)
> ------------------------------------------------------
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
