tidb-server v2.1.0-rc.4

SQL Optimizer

• Fix the issue that column pruning of UnionAll is incorrect in some cases #7941
• Fix the issue that the result of the UnionAll operator is incorrect in some cases #8007

SQL Execution Engine

• Fix the precision issue of the AVG function #7874
• Support using the EXPLAIN ANALYZE statement to check the runtime statistics including the execution time and the number of returned rows of each operator during the query execution process #7925
• Fix the panic issue of the PointGet operator when a column of a table appears multiple times in the result set #7943
• Fix the panic issue caused by too large values in the Limit subclause #8002
• Fix the panic issue during the execution process of the AddDate/SubDate statement in some cases #8009

Statistics

• Fix the issue of judging the prefix of the histogram low-bound of the combined index as out of range #7856
• Fix the memory leak issue caused by statistics collecting #7873
• Fix the panic issue when the histogram is empty #7928
• Fix the issue that the histogram bound is out of range when the statistics is being uploaded #7944
• Limit the maximum length of values in the statistics sampling process #7982

Server

• Refactor Latch to avoid misjudgment of transaction conflicts and improve the execution performance of concurrent transactions #7711
• Fix the panic issue caused by collecting slow queries in some cases #7874
• Fix the panic issue when ESCAPED BY is an empty string in the LOAD DATA statement #8005
• Complete the “coprocessor error” log information #8006

Compatibility

• Set the Command field of the SHOW PROCESSLIST result to Sleep when the query is empty #7839

Expressions

• Fix the constant folding issue of the SYSDATE function #7895
• Fix the issue that SUBSTRING_INDEX panics in some cases #7897

DDL

• Fix the stack overflow issue caused by throwing the invalid ddl job type error #7958
• Fix the issue that the result of ADMIN CHECK TABLE is incorrect in some cases #7975