Variable name Change type Description tidb_stats_cache_mem_quota �→ Newly added This vari- able sets the mem- ory quota for the TiDB statis- tics cache. 2.2.2.2 Configuration file parameters 57 Configuration functions Y Y Y Y Y Y Y Y Miscellaneous functions Y Y Y Y Y Y Y Y Operators Y Y Y Y Y Y Y Y Character sets and collations 1 Y Y Y Y Y Y Y Y User-level lock Y N N N N N N N 2.3.2 Indexing and constraints indexes #1793 • SPATIAL (also known as GIS/GEOMETRY) functions, data types and indexes #6347 • Character sets other than ascii, latin1, binary, utf8, utf8mb4, and gbk. • SYS schema • Optimizer trace • XML Functions

r(x, nil), r(y, 1) Under snapshot isolation, T1 and T2 may execute concurrently, because their write sets don’t intersect. However, every transaction should observe a snapshot consistent with applying those failure dur- ing that period could destroy acknowledged writes, or render the cluster partly, or totally, unusable. In our tests, default-sized clusters reached a fully-replicated state in 1-2 minutes; .. for update to prevent write skew: where trans- actions read intersecting data, but their write sets are disjoint. Using select ... for update on a read is somewhat like promoting that read to a write

set since v5.4.0 Before v5.4.0, TiDB supports ascii, binary, latin1, utf8, and utf8mb4 character sets. To better support Chinese users, TiDB supports the GBK character set since v5.4.0. Af- ter enabling Window functions Y Y Y Y Y Y Miscellaneous functions Y Y Y Y Y Y Operators Y Y Y Y Y Y Character sets and collations 1 Y Y Y Y Y Y 1TiDB incorrectly treats latin1 as a subset of utf8. See TiDB #18955 global # Global configuration. 64 chroot /var/lib/haproxy # Changes the current directory and �→ sets superuser privileges for the startup process to improve �→ security. pidfile /var/run/haproxy.pid

Printf("getPlayer: %+v\n", testPlayer) // Create players with bulk inserts. Insert 1919 players totally, with 114 players per batch. bulkInsertPlayers := make([]Player, 1919, 1919) total, batch := 1919 Printf("getPlayer: %+v\n", testPlayer) // Create players with bulk inserts. Insert 1919 players totally, with 114 players per batch. err = bulkInsertPlayers(db, randomPlayers(1919), 114) if err != nil testPlayer.getCoins(), testPlayer.getGoods()); // Create players with bulk inserts. Insert 1919 players totally, with 114 players per �→ batch. int addedCount = dao.bulkInsertRandomPlayers(1919, 114); System

46 Variable name Change type Description tidb_analyze_distsql_scan_concurrency �→ Newly added Sets the concur- rency of the scan opera- tion when execut- ing the ANALYZE �→ opera- tion. The default raftstore �→ . �→ periodic �→ - �→ full �→ - �→ compact �→ - �→ start �→ - �→ times �→ Newly added Sets the specific times that TiKV initiates periodic full com- paction. The default value [] means periodic parame- ter Change type Description TiCDC sink. �→ cloud �→ - �→ storage �→ - �→ config �→ Newly added Sets the auto- matic cleanup of histor- ical data when replicat- ing data to object storage. 2.2.2.4 System

Change type Description TiDB tikv- �→ client �→ . �→ copr �→ -req �→ - �→ timeout �→ Newly added Sets the timeout of a single Copro- cessor request. 45 Configuration file Configuration parame- ter Description TiKV raftstore �→ . �→ region �→ - �→ compact �→ -min �→ - �→ redundant �→ - �→ rows Modified Sets the number of redun- dant MVCC rows required to trigger RocksDB com- paction. Starting from v7.5.0 raftstore �→ . �→ region �→ - �→ compact �→ - �→ redundant �→ - �→ rows �→ - �→ percent �→ Modified Sets the percent- age of redun- dant MVCC rows required to trigger RocksDB com- paction. Starting from

default and sets the mem- ory limit for a TiDB in- stance to 80% of the total mem- ory by de- fault. 53 Variable name Change type Description default_password_lifetime �→ Newly added Sets the global Variable name Change type Description tidb_index_merge_intersection_concurrency �→ Newly added Sets the maxi- mum concur- rency for the inter- section opera- tions that index merge per- forms. It is functions Y Y Y Y Y Y Y Y Miscellaneous functions Y Y Y Y Y Y Y Y Operators Y Y Y Y Y Y Y Y Character sets and collations 1 Y Y Y Y Y Y Y Y User-level lock Y Y N N N N N N 2.3.2 Indexing and constraints

Configuration file Configuration parame- ter Change type Description TiDB log. �→ timeout �→ Newly added Sets the timeout for log- writing opera- tions in TiDB. In case of a disk failure that prevents logs from Change type Description TiKV region- �→ compact �→ -min �→ - �→ redundant �→ - �→ rows Newly added Sets the number of redun- dant MVCC rows required to trigger RocksDB com- paction. The default value is is 50000. TiKV region- �→ compact �→ - �→ redundant �→ - �→ rows �→ - �→ percent �→ Newly added Sets the percent- age of redun- dant MVCC rows required to trigger RocksDB com- paction. The default value

For more information, see documentation. 2.2.1.2 Reliability • Support streaming cursor result sets (experimental) #54526 @YangKeao When the application code retrieves the result set using Cursor Fetch node, but gradually reads data to the TiDB node as the client reads. When TiDB processes large result sets, this feature reduces the memory usage of the TiDB node and improves the stability of the cluster Y Y Y Y Miscellaneous functions Y Y Y Y Y Y Y Y Y Y Y Operators Y Y Y Y Y Y Y Y Y Y Y Character sets and collations 1 Y Y Y Y Y Y Y Y Y Y Y User-level lock Y Y Y Y Y Y Y N N N N 2.3.2 Indexing and

Variable name Change type Description tidb_ �→ auto �→ _ �→ analyze �→ _ �→ concurrency �→ Newly added Sets the concur- rency within a single auto- matic statis- tics collec- tion task. Before v8.4.0, this Change type Description tidb_ �→ instance �→ _ �→ plan �→ _ �→ cache �→ _max �→ _ �→ size Newly added Sets the maxi- mum mem- ory usage for In- stance Plan Cache. tidb_ �→ instance �→ _ �→ plan �→ _ �→ cache Y Y Miscellaneous functions Y Y Y Y Y Y Y Y Y Y Y Y Operators Y Y Y Y Y Y Y Y Y Y Y Y Character sets and collations 1 Y Y Y Y Y Y Y Y Y Y Y Y User-level lock Y Y Y Y Y Y Y Y N N N N 2.3.2 Indexing