# TiDB 2.0.6 Release Notes

On August 6, 2018, TiDB 2.0.6 is released. Compared with TiDB 2.0.5, this release has great improvement in system compatibility and stability.

## TiDB

• Improvements
• Make “set system variable” log shorter to save disk space #7031
• Record slow operations during the execution of ADD INDEX in the log, to make troubleshooting easier #7083
• Reduce transaction conflicts when updating statistics #7138
• Improve the accuracy of row count estimation when the values pending to be estimated exceeds the statistics range #7185
• Choose the table with a smaller estimated row count as the outer table for Index Join to improve its execution efficiency #7277
• Add the recover mechanism for panics occurred during the execution of ANALYZE TABLE, to avoid that the tidb-server is unavailable caused by abnormal behavior in the process of collecting statistics #7228
• Return NULL and the corresponding warning when the results of RPAD/LPAD exceed the value of the max_allowed_packet system variable, compatible with MySQL #7244
• Set the upper limit of placeholders count in the PREPARE statement to 65535, compatible with MySQL #7250
• Bug Fixes
• Fix the issue that the DROP USER statement is incompatible with MySQL behavior in some cases #7014
• Fix the issue that statements like INSERT/LOAD DATA meet OOM aftering opening tidb_batch_insert #7092
• Fix the issue that the statistics fail to automatically update when the data of a table keeps updating #7093
• Fix the issue that the firewall breaks inactive gPRC connections #7099
• Fix the issue that prefix index returns a wrong result in some scenarios #7126
• Fix the panic issue caused by outdated statistics in some scenarios #7155
• Fix the issue that one piece of index data is missed after the ADD INDEX operation in some scenarios #7156
• Fix the wrong result issue when querying NULL values using the unique index in some scenarios #7172
• Fix the messy code issue of the DECIMAL multiplication result in some scenarios #7212
• Fix the wrong result issue of DECIMAL modulo operation in some scenarios #7245
• Fix the issue that the UPDATE/DELETE statement in a transaction returns a wrong result under some special sequence of statements #7219
• Fix the panic issue of the UNION ALL/UPDATE statement during the process of building the execution plan in some scenarios #7225
• Fix the issue that the range of prefix index is calculated incorrectly in some scenarios #7231
• Fix the issue that the LOAD DATA statement fails to write the binlog in some scenarios #7242
• Fix the wrong result issue of SHOW CREATE TABLE during the execution process of ADD INDEX in some scenarios #7243
• Fix the issue that panic occurs when Index Join does not initialize timestamps in some scenarios #7246
• Fix the false alarm issue when ADMIN CHECK TABLE mistakenly uses the timezone in the session #7258
• Fix the issue that ADMIN CLEANUP INDEX does not clean up the index in some scenarios #7265
• Disable the Read Committed isolation level #7282

## TiKV

• Improvements
• Enlarge scheduler's default slots to reduce false conflicts
• Reduce continuous records of rollback transactions, to improve the Read performance when conflicts are extremely severe
• Limit the size and number of RocksDB log files, to reduce unnecessary disk usage in long-running condition
• Bug Fixes
• Fix the crash issue when converting the data type from string to decimal