old-value- �→ cache- �→ memory- �→ quota Newly added Sets the upper limit of memory usage by TiCDC old values. The default value is 512MB. TiKV con- figuration file sink- �→ memory- �→ quota Newly added Sets projection result is empty #23887 – Fix the issue of wrong query results when a column contains NULL values in some cases #23891 – Forbid generating MPP plans when the scan contains virtual columns #23886 up after the file dictionary file is damaged #9886 – Fix a TiCDC OOM issue caused by reading old values #9996 #9981 – Fix the issue of empty value in the secondary index for the clustered primary key column

in the configuration file before the �→ upgrade already exist, TiDB will automatically update the values of �→ the configured items to those of the corresponding system variables �→ during the upgrade process the foundation for implementing Change Data Capture and incremental backup and restore. • Data is scoped according to different usage and supports co-existence of a single TiDB cluster, Transactional KV clusters inherit the configuration from the configuration file. New clusters use the new default values, which means Prepared Plan Cache is enabled by default and each session can cache 100 plans at most

multiple TiDB servers or allocated sequentially. It is recommended that you do not mix default values and custom values. Otherwise, you might encounter the Duplicated Error error message. • You can use the TABLE t(id INT UNIQUE KEY AUTO_INCREMENT); Query OK, 0 rows affected (0.05 sec) mysql> INSERT INTO t VALUES(),(),(); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> SELECT ZEROFILL attribute. MySQL 8.0 deprecates this feature, and it is recommended to instead pad numeric values in your application. 2.7 TiDB Limitations This document describes the common usage limitations

issue that might occur when the Date_Format function is called with the STRING type argument and NULL values • Tools – TiCDC * Fix a bug that TiCDC owner exits abnormally when refreshing the checkpoint multiple TiDB servers or allocated sequentially. It is recommended that you do not mix default values and custom values. Otherwise, you might encounter the Duplicated Error error message. • You can use the TABLE t(id INT UNIQUE KEY AUTO_INCREMENT); Query OK, 0 rows affected (0.05 sec) mysql> INSERT INTO t VALUES(),(),(); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> SELECT

Lightning stops reading source data and writing temporary files. Instead, 41 it writes the sorted key-values to TiKV first, and then continues the import process after TiDB Lightning deletes the local temporary packet” 2.4.2 Features that are different from MySQL 2.4.2.1 Auto-increment ID • In TiDB, the values (IDs) of an auto-incremental column are globally unique. They are incremental on a single TiDB server are not necessarily allocated sequentially. It is recommended that you do not mix default values and custom values. Otherwise, you might encounter the Duplicated Error error message. • You can use the

engine automatically segregates large values exceeding 32 KB from RocksDB’s LSM Tree, and stores them separately in Titan to optimize the handling of large values. The Titan engine is completely compatible effect, but also enhances performance 38 in write, update, and point-query scenarios involving large values. Additionally, in Range Scan scenarios, the Titan engine’s optimization has resulted in performance Description TiKV blob- �→ file �→ - �→ compression �→ Modified The algo- rithm used for com- pressing values in Titan, which takes value as the unit. Starting from TiDB v7.6.0, the default compres- sion algo-

tions. v7.5.0 in- troduces a new value option columns, which uses the explic- itly specified column values to calculate the partition number. 53 Configuration file Configuration parame- ter Change type 2.4.2 Differences from MySQL 2.4.2.1 Auto-increment ID • In TiDB, the auto-incremental column values (IDs) are globally unique and incremen- tal within a single TiDB server. To make the IDs incremental necessarily allocated sequentially, so it is recommended that you avoid mix- ing default and custom values to prevent encountering the Duplicated Error message. • You can use the tidb_allow_remove_auto_inc

pingcap.com/tidb/v7.1/generated-columns" target=" �→ _blank">Generated columns (GA) Values in a generated column are calculated by a SQL expression in the �→ column definition in real time multi-valued indexes become generally available (GA) #39592 @xiongjiwei @qw4990 @YangKeao Filtering the values of an array in a JSON column is a common operation, but normal indexes cannot help speed up such database. When creating a table, you can define that the value of a column is calculated based on the values of other columns in the table, rather than being explicitly inserted or updated by users. This generated

and log.enable �→ - �→ timestamp �→ . If you only set the old parameters, and their values are set to non-default values, the old parameters remain compatible with the new parameters. If both old and new • Fix the issue that no error is reported for the Inf or NAN value when inserting floating- point values #30148 • Fix the issue that the REPLACE statement incorrectly changes other rows when the auto ID performance of data replication – Improve TiFlash performance and stability by tuning the default values of some configuration items. In an HTAP hybrid load, the performance of simple queries on a single

MAX_REQUEST_UNIT_READ, MAX_PROCESSED_KEYS) in the Statement Summary Ta- bles to determine the condition values based on historical execution. For more information, see documentation. • Support switching resource verify old values in Update or Delete events #10969 @3AceShowHand Starting from v8.4.0, TiDB and TiCDC introduce the Checksum V2 algorithm to address issues of Checksum V1 in verifying old values in Update from boolean to enu- mera- tion, the default value is changed from OFF to null, and the op- tional values TABLE and GLOBAL are added. In ad- dition, it now sup- ports cluster- level scatter- ing policy to