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Bug#54678: InnoDB, TRUNCATE, ALTER, I_S SELECT, crash or deadlock - Incompatible change: truncate no longer resorts to a row by row delete if the storage engine does not support the truncate method. Consequently, the count of affected rows does not, in any case, reflect the actual number of rows. - Incompatible change: it is no longer possible to truncate a table that participates as a parent in a foreign key constraint, unless it is a self-referencing constraint (both parent and child are in the same table). To work around this incompatible change and still be able to truncate such tables, disable foreign checks with SET foreign_key_checks=0 before truncate. Alternatively, if foreign key checks are necessary, please use a DELETE statement without a WHERE condition. Problem description: The problem was that for storage engines that do not support truncate table via a external drop and recreate, such as InnoDB which implements truncate via a internal drop and recreate, the delete_all_rows method could be invoked with a shared metadata lock, causing problems if the engine needed exclusive access to some internal metadata. This problem originated with the fact that there is no truncate specific handler method, which ended up leading to a abuse of the delete_all_rows method that is primarily used for delete operations without a condition. Solution: The solution is to introduce a truncate handler method that is invoked when the engine does not support truncation via a table drop and recreate. This method is invoked under a exclusive metadata lock, so that there is only a single instance of the table when the method is invoked. Also, the method is not invoked and a error is thrown if the table is a parent in a non-self-referencing foreign key relationship. This was necessary to avoid inconsistency as some integrity checks are bypassed. This is inline with the fact that truncate is primarily a DDL operation that was designed to quickly remove all data from a table. |
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| .. | ||
| CMakeLists.txt | ||
| db2i_blobCollection.cc | ||
| db2i_blobCollection.h | ||
| db2i_charsetSupport.cc | ||
| db2i_charsetSupport.h | ||
| db2i_collationSupport.cc | ||
| db2i_collationSupport.h | ||
| db2i_constraints.cc | ||
| db2i_conversion.cc | ||
| db2i_errors.cc | ||
| db2i_errors.h | ||
| db2i_file.cc | ||
| db2i_file.h | ||
| db2i_global.h | ||
| db2i_iconv.h | ||
| db2i_ileBridge.cc | ||
| db2i_ileBridge.h | ||
| db2i_ioBuffers.cc | ||
| db2i_ioBuffers.h | ||
| db2i_misc.h | ||
| db2i_myconv.cc | ||
| db2i_myconv.h | ||
| db2i_rir.cc | ||
| db2i_safeString.h | ||
| db2i_sqlStatementStream.cc | ||
| db2i_sqlStatementStream.h | ||
| db2i_validatedPointer.h | ||
| ha_ibmdb2i.cc | ||
| ha_ibmdb2i.h | ||
| Makefile.am | ||
| plug.in | ||