These notes describe the difference between Apache Derby release 10.11.0.0 and the preceding release 10.10.2.0.
The most up to date information about Derby releases can be found on the Derby download page.
Apache Derby is a pure Java relational database engine using standard SQL and JDBC as its APIs. More information about Derby can be found on the Apache web site. Derby functionality includes:
Java and JDBC versions supported:
This is a feature release. The following new features were added:
The following issues are addressed by Derby release 10.11.0.0. These issues are not addressed in the preceding 10.10.2.0 release.
|DERBY-6644||Support standard syntax for altering column nullability|
|DERBY-6643||ALTER TABLE columnAlteration syntax needs fixing|
|DERBY-6638||Remove unnecessary use of reflection in SignatureChecker|
|DERBY-6633||Remove DOM level 3 XPath requirement from description of XML operators|
|DERBY-6629||Restrict privileged operation in CreateXMLFile|
|DERBY-6624||Use javax.xml.xpath interfaces for XPath support|
|DERBY-6615||Remove unused newInstance() method in BaseMonitor|
|DERBY-6611||Broken link in API docs to derby.drda.keepAlive documentation|
|DERBY-6609||Documentation for SQL features should reflect current standard|
|DERBY-6605||"Derby support for SQL-92 features" topic in Reference Manual needs updating|
|DERBY-6602||LuceneQueryVTI handles NULL key values inconsistently|
|DERBY-6601||Clean up Java EE compliance section of Reference Manual|
|DERBY-6599||Incorrect quoting of 42ZB4 message|
|DERBY-6598||Document permissions recommendations for JAR procedures|
|DERBY-6597||LUCENESUPPORT.LISTINDEXES() fails with FileNotFoundException|
|DERBY-6596||LUCENESUPPORT routines should check for NULL arguments|
|DERBY-6595||CheckToursDBTest failed while updating sequence value on disk|
|DERBY-6594||Typos in "Listing indexes" topic of the tools guide|
|DERBY-6591||Minor tweaks needed on new ij commands|
|DERBY-6587||Foreign Key constraint not matched when using UUID in a composite foreign key when using SYSCS_UTIL.SYSCS_IMPORT_TABLE|
|DERBY-6585||add HoldForConnection ij command to match NoHoldForConnection|
|DERBY-6581||Document simple case syntax|
|DERBY-6580||Document the new SYSCS_UTIL.SYSCS_PEEK_AT_IDENTITY function|
|DERBY-6577||Quantified comparison returns wrong result in CASE, COALESCE, IN and BETWEEN|
|DERBY-6576||A immediate Fk constraint blows up iff its referenced PK is deferred and we modify a duplicate key column|
|DERBY-6571||Document deferrable constraints|
|DERBY-6567||Incorrect nullability for CASE expression with parameter|
|DERBY-6566||Simplify handling of untyped nulls in CASE and NULLIF expressions|
|DERBY-6564||Document the experimental, optional LuceneSupport tool.|
|DERBY-6563||NOT elimination for CASE expressions is broken|
|DERBY-6561||Organization topics of some manuals need updating|
|DERBY-6560||Reference manual says ELSE clause is required in CASE expressions|
|DERBY-6559||A immediate Fk constraint blows up iff its referenced PK is deferred and we delete a duplicate|
|DERBY-6554||Too much contention followed by assert failure when accessing sequence in transaction that created it|
|DERBY-6553||Sequence generator makes CREATE TRIGGER fail with internal error|
|DERBY-6552||The public api includes methods inherited from superclasses which aren't in the public api and so have no javadoc comments|
|DERBY-6545||Should not be able to add a default to an identity column|
|DERBY-6543||Syntax error when reference to transition variable has whitespace around it|
|DERBY-6542||Improve the concurrency of identity columns by using SYS.SYSSEQUENCES|
|DERBY-6540||Schema-qualified table names could be mistaken for transition tables|
|DERBY-6537||StringUtil.fromHexString is used to convert encryptionKey to byte|
|DERBY-6535||Remove storageFactory field from subclasses of InputStreamFile|
|DERBY-6534||Remove StorageFile.getURL() and its implementations|
|DERBY-6527||Fix errors in foreign keys documentation|
|DERBY-6526||Document the MERGE statement|
|DERBY-6521||Improve error handling when restricting file permissions|
|DERBY-6518||JVMInfo should not use parseFloat() to parse java.specification.version|
|DERBY-6515||ij doesn't list its command NoHoldForConnection in the help menu|
|DERBY-6511||java.lang.NoSuchMethodError chaining a function and procedure|
|DERBY-6505||Clean up dead code in FileUtil|
|DERBY-6504||change AllocPage.ReadContainerInfo to catch ArrayIndexOutOfBoundsException and turn it into Derby error.|
|DERBY-6503||Starting network server on a network drive fails with JDK 7 on Windows|
|DERBY-6496||Optional tool registration may fail because the CompilerContext is not always available at execution time.|
|DERBY-6493||Improve reporting of exceptions wrapped in InvocationTargetException|
|DERBY-6488||Get rid of the EmbedSQLException class|
|DERBY-6484||Include SQLState in client exception messages|
|DERBY-6480||Oracle Java documentation URLs need updating|
|DERBY-6478||Fix language about supported DataSources for Compact Profiles|
|DERBY-6469||Change the documentation to reflect new RDBNAM limit of 1024 bytes|
|DERBY-6467||Document context-aware table functions.|
|DERBY-6464||Improve the encapsulation of various compiler classes|
|DERBY-6462||Provide more information about database name and path syntax|
|DERBY-6459||Remove Class.forName calls that load JDBC driver from Derby samples/demos|
|DERBY-6458||The Reference Manual should state that the year, month, and day components of a timestamp must be positive integers.|
|DERBY-6454||DROP TABLE documentation could clarify how triggers are handled|
|DERBY-6453||Remove dead code in InsertResultSet and flag skipCheckConstraints|
|DERBY-6447||Use StrictMath for more functions in SYSFUN|
|DERBY-6440||Connections opened by ForeignTableVTI never get released|
|DERBY-6434||Incorrect privileges may be required for INSERT and DELETE statements.|
|DERBY-6432||INSERT/UPDATE incorrectly require user to have privilege to execute CHECK constraints on the target table.|
|DERBY-6431||Update Developer's Guide topic to include generated columns|
|DERBY-6429||Privilege checks for UPDATE statements are wrong.|
|DERBY-6423||The expression syntax in CASE's THEN clause doesn't accept boolean value expression|
|DERBY-6421||Cast to UDT in CHECK constraint causes NPE or assert failure|
|DERBY-6420||Clarify how DROP statements work on trigger dependencies|
|DERBY-6419||Make BTree scan honor OPENMODE_LOCK_NOWAIT for row locks.|
|DERBY-6410||ClassCastException when launching derby from windows subst drive|
|DERBY-6390||Document the WHEN clause in the CREATE TRIGGER statement|
|DERBY-6386||Errors in jdbc4.LobStreamTest if derbyclient.jar is first in the classpath|
|DERBY-6378||OFFSET/FETCH NEXT ignored when query is enclosed in parentheses|
|DERBY-6370||dblook doesn't schema-qualify identifiers in trigger actions|
|DERBY-6362||CHECK constraint uses wrong schema for unqualified routine invocations|
|DERBY-6359||Document rolling derby.log file feature|
|DERBY-6350||Provide a rolling file implementation of derby.log|
|DERBY-6330||Simplify StringBuffer use, as they are mutable|
|DERBY-6322||Remove erreoneous warning in NetBeans: superfluous use of super to access inherited member variable|
|DERBY-6321||NetBeans project file: add XML api to source classpath|
|DERBY-6318||Simplify setting of possibly null parameters in XPLAIN descriptors|
|DERBY-6315||Improve test coverage of org.apache.derby.impl.io.InputStreamFile|
|DERBY-6304||Remove unused methods in Predicate|
|DERBY-6296||Simplify PropertyUtil using Properties.stringPropertyNames()|
|DERBY-6292||Use Arrays.copyOf() in FormatableArrayHolder.getArray()|
|DERBY-6291||Improve code coverage of org.apache.derby.iapi.jdbc.BrokeredCallableStatement|
|DERBY-6287||Don't use reflection to call Java 6 methods in FileUtil|
|DERBY-6285||Use factory method to create thread pool for timed login|
|DERBY-6284||Improve test coverage of org.apache.derby.iapi.db.ConnectionInfo|
|DERBY-6276||Convert lang/DB2IsolationLevels.sql to JUnit|
|DERBY-6266||Add ability to print a Derby execution ResultSet as xml.|
|DERBY-6262||Simplify message-generating methods using varargs|
|DERBY-6259||Collapse the level 2 optimizer into its parent module.|
|DERBY-6254||Reduce number of factory methods in StandardException|
|DERBY-6253||Collapse SQLException factories|
|DERBY-6248||nightly regression test failure: testDerby966(org.apache.derbyTesting.functionTests.tests.jdbcapi.XATest)java.sql.SQLFeatureNotSupportedException: The DDM object 0x2408 is not supported. The connection has been terminated.|
|DERBY-6243||Fold Java5ClassFactory into ReflectClassesJava2|
|DERBY-6242||Merge ConcurrentXactFactory into XactFactory|
|DERBY-6241||Remove SinglePool from trunk|
|DERBY-6240||Remove Clock cache manager from trunk|
|DERBY-6236||Remove references to old JVMs (pre-Java 6) from the user guides|
|DERBY-6234||Remove references to BUILTIN authentication from the user guides|
|DERBY-6231||Remove unnecessary checks for UnsupportedEncodingException in the client|
|DERBY-6230||Use the JVM's cache of Number instances in ReuseFactory|
|DERBY-6227||Distinct aggregates don't work well with territory-based collation|
|DERBY-6217||Put all of the security documentation in a single, separate user guide|
|DERBY-6213||Deprecate support for Java 5 and CDC|
|DERBY-6207||Update policy files in java/drda/org/apache/derby/drda|
|DERBY-6206||Cleanup suspect coding practices in misc Derby packages|
|DERBY-6202||Cleanup suspect coding practices in the org.apache.derby.iapi.sql.dictionary package|
|DERBY-6201||Cleanup suspect coding practices in the org.apache.derby.impl.sql.execute.rts package|
|DERBY-6200||Cleanup suspect coding practices in the org.apache.derby.iapi.types package|
|DERBY-6199||Cleanup suspect coding practices in the org.apache.derby.vti package|
|DERBY-6198||Cleanup suspect coding practices in the org.apache.derby.tools package|
|DERBY-6197||Cleanup suspect coding practices in the org.apache.derby.impl.tools.planexporter package|
|DERBY-6195||Cleanup suspect coding practices in the org.apache.derby.impl.tools.ij package.|
|DERBY-6192||Cleanup suspect coding practices in org.apache.derby.iapi.services.property package|
|DERBY-6188||Cleanup suspect coding practices in org.apache.derby.iapi.services.io package|
|DERBY-6186||SYSTRIGGERSRowFactory should use DataDescriptorGenerator to build descriptor|
|DERBY-6184||Clean up warnings in XA transaction id classes|
|DERBY-6182||Cleanup suspect coding practices in org.apache.derby.iapi.error package|
|DERBY-6177||Cleanup suspect coding practices in org.apache.derby.catalog.types|
|DERBY-6169||Reduce visibility of classes and methods under impl/sql|
|DERBY-6168||Clean up registered format ids|
|DERBY-6163||Reduce visibility of methods in subclasses of PageBasicOperation|
|DERBY-6161||Simplify code that handles LOB files|
|DERBY-6138||org.apache.derbyTesting.functionTests.tests.store.ClassLoaderBootTest fails with sealing violation: package org.apache.derby.iapi.services.sanity is sealed depending on classpath order|
|DERBY-6133||simple array index typo|
|DERBY-6128||Examine Derby classes to determine if we need to add serialVersionUID to any of them|
|DERBY-6125||Code clean up in client driver.|
|DERBY-6096||OutOfMemoryError with Clob or Blob hash join: DataTypeDescriptor.estimatedMemoryUsage() has no case for BLOB or CLOB so would underestimate memory usage for those types at zero|
|DERBY-6075||Use modern collections in impl/sql/compile|
|DERBY-5840||Clean up compiler warnings introduced by using Java 5 language features|
|DERBY-5615||NPE in Store when running SELECT in a read-only database accessed via the classpath subprotocol when authentication, authorization, and Java security are turned on|
|DERBY-5317||NullPointerException in org.apache.derby.client.net.Request.sendBytes() with client|
|DERBY-5313||Assert failure with CASE expression in GROUP BY clause|
|DERBY-5196||Correct the layout of log.ctrl as described on the Derby web site|
|DERBY-5111||NullPointerException on unique constraint violation with unique index|
|DERBY-4805||Increase the length of the RDBNAM field in the DRDA implementation|
|DERBY-4750||add documentation to declare global temporary tables to explain expected behavior when used with XA transactions.|
|DERBY-4478||Use AtomicLong for XactFactory.tranId|
|DERBY-4403||Assert failure (sane) or NullPointerException (insane) when attempting to GROUP BY expression containing scalar subquery|
|DERBY-4381||Connection to Derby database using jar subprotocol doesn't work if the path has round bracket in it|
|DERBY-3573||Argument checking for ResultSet.setFetchSize(int) is incorrect|
|DERBY-3155||Support for SQL:2003 MERGE statement|
|DERBY-2438||Remove JDBC20Translation and JDBC30Translation classes|
|DERBY-2423||Embedded and client differ on ResultSetMetaData.isCurrency() value for DECIMAL and NUMERIC columns|
|DERBY-2041||Trigger should register a dependency on tables and columns used in its body|
|DERBY-2002||Case expression allows NULL in all parts of <result>|
|DERBY-1997||Misleading text in WwdEmbedded demo source file for Working With Derby|
|DERBY-1984||Re-factor JDBC classes to remove support for JDBC 2|
|DERBY-1576||Extend the CASE expression syntax for "simple case"|
|DERBY-1028||Change constructors in NetConnection classes to use LogWriter instead of NetLogWriter|
|DERBY-673||Get rid of the NodeFactory|
|DERBY-534||Support use of the WHEN clause in CREATE TRIGGER statements|
|DERBY-532||Support deferrable constraints|
Compared with the previous release (10.10.2.0), Derby release 10.11.0.0 introduces the following new features and incompatibilities. These merit your special attention.
More type mismatches are detected in THEN and ELSE clauses of CASE expressions.
If a CASE expression has a THEN clause or an ELSE clause that consists of an explicitly typed NULL, and the type is not compatible with all the other THEN and ELSE clauses of the CASE expression, an exception will be thrown.
For example, the following CASE expression
CASE WHEN a=b THEN 1 ELSE CAST(NULL AS CHAR(10)) END
will cause the following error
ERROR 42X89: Types 'CHAR' and 'INTEGER' are not type compatible. Neither type is assignable to the other type.
In Derby versions from 10.3 to 10.10, the same expression would have succeeded, and it would have evaluated either to 1 or to NULL with type INTEGER.
The old behaviour was unintended and could hide bugs in SQL statements.
Applications that cast NULL to an incorrect type in a THEN or ELSE clause, should rewrite that clause to use either an implicitly typed NULL or an explicitly typed null of a type compatible with the other THEN or ELSE clauses.
For example, the failing expression mentioned above could be rewritten to the following:
CASE WHEN a=b THEN 1 ELSE NULL END
The NULL in the ELSE clause will get its type inferred from the type of the THEN clause. That is, INTEGER.
If an explicitly typed NULL is preferred, the expression could also be rewritten to the following:
CASE WHEN a=b THEN 1 ELSE CAST(NULL AS INTEGER) END
You can no longer add a default to an identity column.
You can no longer change an identity column as follows:
alter table MyTable alter column MyIdentityColumn default 99;
Previously, that statement would have added a default to MyTable.MyIdentityColumn and the column would have ceased to be an identity column.
The previous behavior violated the SQL Standard.
Applications which need to change an identity column into a non-identity column with a default should be re-coded to do something like this:
alter table MyTable add column dummy int default 99; update MyTable set dummy = MyIdentityColumn; alter table MyTable drop column MyIdentityColumn; rename column MyTable.dummy to MyIdentityColumn;
Identity columns are now backed by internal sequence generators.
In previous releases, identity values were managed in the heavily used SYS.SYSCOLUMNS table. This caused lock contention among insert statements.
After hard-upgrading to 10.11, identity columns will now be backed by internal sequence generators. This should reduce lock contention among insert statements. It also means that identity columns now pre-allocate ranges of upcoming values, just as sequences do. Applications should take extra care to shutdown databases gracefully before exiting. If an application crashes or does not close its databases gracefully, then the unused, pre-allocated identity values will leak; the user will see a gap between the last identity value inserted before the crash and the first identity value inserted after restarting the application.
In addition, after hard-upgrading to 10.11, users will no longer be able to query the SYS.SYSCOLUMNS table in order to discover the next value which will be inserted into an identity column. Instead, users should use the new SYSCS_UTIL.SYSCS_PEEK_AT_IDENTITY() system function. Users should never directly query SYS.SYSCOLUMNS or SYS.SYSSEQUENCES. Directly querying these catalogs will acquire read locks which may throttle application throughput.
This change was made in order to improve the throughput/performance of inserts into tables which have identity columns.
After hard-upgrading to 10.11, be sure that your application closes its databases gracefully so that you do not leak unused, pre-allocated identity values. Individual databases may be closed via the shutdown=true attribute:
DriverManager.getConnection( "jdbc:derby:myDatabase;shutdown=true" );
Alternatively, all open databases may be closed by shutting down the engine:
DriverManager.getConnection( "jdbc:derby:;shutdown=true" );
If your application is prone to ungraceful crashes and you cannot tolerate leaking unused, pre-allocated identity values, then you can adjust the maximum number of unused values per identity column. You can do this be setting the derby.language.sequence.preallocator database property. The default setting for this property is 100:
call syscs_util.syscs_set_database_property( 'derby.language.sequence.preallocator', '10' );
In addition, after hard-upgrading to 10.11, applications should be adjusted so that they call SYSCS_UTIL.SYSCS_PEEK_AT_IDENTITY() in order to discover the next value which will be inserted into an identity column. Applications should no longer directly query SYS.SYSCOLUMNS for this information:
values SYSCS_UTIL.SYSCS_PEEK_AT_IDENTITY( 'APP', 'MYTABLE' );
Implementation of LOG10, COSH, SINH and TANH changed.
Apache Derby has built-in logarithmic and hyperbolic functions that live in the SYSFUN schema. Most, but not all, of these functions are implemented as calls to the corresponding methods in the java.lang.StrictMath class. In this release, more functions than before use the methods in the java.lang.StrictMath class.
Specifically, the implementation of the LOG10, COSH, SINH and TANH functions have changed, and for some input values the values returned by those methods have changed.
For example, the function call LOG10(1000) would return 2.9999999999999996 in the previous versions. In this version, it will return 3.0.
The function call TANH(1000) would fail with
ERROR 22003: The resulting value is outside the range for the data type DOUBLE.
in previous versions. In this version, it will succeed and return 1.0.
Using the java.lang.StrictMath class instead of custom implementations makes the functions return more accurate results. It also fixes issues where the custom implementations experienced overflow in intermediate results and failed instead of returning a result.
The new implementations are used automatically after upgrade without any changes to the application. If your application uses any of the affected functions, you should check that it doesn't depend on these functions returning the exact same results before and after the upgrade.
If one of the affected functions is used in the generation expression of a generated column, the value of the generated column will not be recalculated automatically on upgrade. It will be recalculated when a column referenced in the generation expression is updated, or if the generated column is updated to its DEFAULT value. To force the generated values to be recalculated sooner after upgrade, you can issue an UPDATE statement such as:
UPDATE t SET generated_column = DEFAULT
Privileges required for INSERT and DELETE statements have changed.
Fewer privileges are now required to execute INSERT and DELETE statements.
In previous versions, INSERT and DELETE statements demanded that the user enjoy EXECUTE privilege on functions and USAGE privilege on types mentioned by the target table's check constraints, generated columns, and triggers. Those privileges are no longer required by INSERT and DELETE statements. INSERT and DELETE statements which previously failed due to insufficient privileges may succeed now.
This change makes Derby conform better to the SQL Standard.
Security may now be tightened for applications which run with SQL authorization enabled. Those applications may revoke EXECUTE and USAGE privileges which are no longer necessary in order to run INSERT and DELETE statements.
Privileges required for UPDATE statements have changed.
In previous versions, UPDATE statements demanded that the user enjoy UPDATE privilege on all columns from the target table which were mentioned in the WHERE clause. Now Derby requires SELECT privilege on those columns, instead.
In previous versions, UPDATE statements demanded more privileges than the SQL Standard required. In particular, UPDATE statements required...
Now Derby no longer demands these overbroad privileges. However, Derby does require SELECT privilege instead of UPDATE privilege on columns from the target table which are mentioned in the WHERE clause.
This change makes Derby conform better to the SQL Standard.
In applications which run with SQL authorization enabled, an UPDATE statement may now fail because the application has not granted the user SELECT privilege on all target table columns mentioned in the statement's WHERE clause. Those applications should grant users the appropriate SELECT privileges.
In addition, applications may now tighten their security by revoking UPDATE, EXECUTE, and USAGE privileges which are no longer necessary in order to run UPDATE statements.
Derby no longer runs on Java 5 and CDC.
Previous releases of Derby ran on Java 5 and on the small device CDC platform. The 10.11 release family only runs on Java 6 and higher JVMs.
Applications currently running on Java 5 or CDC will not be able to use Derby 10.11. Customers must upgrade their Java platform before installing Derby 10.11.
Previously, Derby's public javadoc included two branches: one for applications which ran on Java 5 and CDC, and another for applications which ran on Java 6 and higher. Now there is one set of public javadoc intended for use on all supported JVMs. Applications are encouraged to use the following Derby DataSources when running on a full Java SE/EE JVM:
...and the following DataSources when running on Java 8's small-device compact profile 2:
For backward compatibility reasons, Derby continues to include the following DataSources. However, they are vacuous extensions of their superclasses now and may be removed in the future. Applications are encouraged to migrate away from these DataSources and to use the DataSources listed above instead:
The older Java platforms are no longer being actively developed and they may contain well-known security vulnerabilities. The Java community is encouraged to migrate to modern, more secure JVMs which are being actively developed. Users interested in running Derby on small devices are encouraged to use Java 8's compact profile 2.
Customers who use Java 5 or CDC will need to upgrade their Java platform if they want to use features introduced by Derby 10.11. Applications are encouraged to migrate to the supported DataSources listed above.
Due to a bug introduced in Derby 10.8, the serialized version number of the class EmbeddedConnectionPoolDataSource40 has changed in Derby 10.8 and later.
Serialized objects for the class EmbeddedConnectionPoolDataSource40 produced by a Derby version 10.7 or older would not be readable with this version of Derby.
Estimates have changed for the memory needed when hash-joining LOB-bearing tables.
In previous releases, BLOBs and CLOBs held in memory were estimated to take zero bytes. This would mean that hash joins with many objects of type BLOB or CLOB could use a large amount of memory. That might improve performance. However, it could cause OutOfMemory errors. After the change for DERBY-6096, hash joins may spill to disk earlier and thus run slower.
BLOBs and CLOBs did not have a maximum memory limit for hash joins. Now they have the default limit of 1048576 (1MB). This limit can be overridden by setting the derby.language.maxMemoryPerTable property.
Hash joins of LOB-bearing tables were raising OutOfMemory errors and crashing the engine.
To allow BLOB/CLOB (and all) hash joins to use more memory, set the Derby property derby.language.maxMemoryPerTable to be the number of bytes you would like to allow for each hash join.
Dropping objects mentioned by triggers now fails.
When DROP TABLE/VIEW/PROCEDURE/FUNCTION/SYNONYM is invoked on an object which is used by a trigger in a triggered SQL statement, the DROP operation now fails and the object is not dropped. In previous releases, those operations would have succeeded, and an exception would have been thrown the next time the dependent trigger fired.
The message text of the new SQLException looks like this:
ERROR X0Y25: Operation 'DROP TABLE' cannot be performed on object 'T' because TRIGGER 'TR' is dependent on that object.
The new exception is thrown only if the trigger was created with version 10.11 or higher. If the dependent trigger was created with an older version, the DROP operation will succeed, and an exception will be thrown the next time the trigger fires.
The previous behavior dropped objects and made other objects invalid. That caused subsequent errors. The new behavior helps prevent such problems.
Also, the new behavior makes DROP TABLE/VIEW/PROCEDURE/FUNCTION/SYNONYM consistent with DROP TYPE/SEQUENCE/DERBY AGGREGATE, ALTER TABLE ... DROP COLUMN and REVOKE. Those statements already failed when there was a dependent trigger.
Applications that drop objects used in triggered SQL statements, must drop the dependent trigger before dropping the dependency.
CASE expressions require at least one result expression with a known type.
Earlier versions allowed CASE expressions where all the result expressions (then THEN and ELSE clauses) were untyped NULLs or a mix of untyped NULLs and untyped parameters. Now the following error will be raised when an application evaluates such an expression:
ERROR 42X87: At least one result expression (THEN or ELSE) of the CASE expression must have a known type.
Applications that use a CASE expression with unknown return type now fail.
The SQL standard requires that at least one of the result expressions is not an untyped NULL.
The previous behavior was inconsistent, as it accepted CASE statements where all result expressions were untyped if they were all NULLs or if they were a mix of NULLs and parameters, but it failed if they all were parameters.
Also, it arbitrarily chose the type CHAR(1) if it could not determine the type of the CASE expression. That type may or may not be the type the application wants. It is safer to fail when the type cannot be determined, and let the application specify explicitly which type it wants.
If an application has a CASE expression that fails because of this change, it should change the CASE expression so that at least one of the THEN or ELSE expressions has a known type.
For example, the following expression
CASE WHEN a = b THEN ? ELSE NULL END
could be changed to
CASE WHEN a = b THEN CAST(? AS CHAR(1)) ELSE NULL END
to make it clear to the compiler that it actually wants the expression to return a value of type CHAR(1).
Derby release 10.11.0.0 was built using the following environment:
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