auto-analyze is unexpectedly triggered outside the specified time pe- riod when new indexes are added before v5.3.0. In v5.3.0, after you set the time period through the tidb_auto_analyze_start_time and ti document • TiDB Lightning Prechecks TiDB Lightning provides the ability to check the configuration before running a migra- tion task. It is enabled by default. This feature automatically performs some routine secondary cluster to a certain snapshot in the primary cluster within 5 minutes, given the condition that before disaster the replication status of TiCDC is normal and replication lag is small. It allows data loss

requests and reports the ServerIsBusy �→ error. The default value is “1024GB”. 2.2.1.3 Others 35 • Before the upgrade, check whether the value of the tidb_evolve_plan_baselines system variable is ON. If from v4.0 to v5.2, the default value of tidb_multi_statement_mode �→ changes from WARN to OFF. • Before the upgrade, check the value of the TiDB configuration feedback-probability �→ . If the value is TLS feature to automatically configure and enable encryption in TiDB. To use the Auto TLS feature, before the TiDB upgrade, set security.auto-tls in the TiDB configuration file to true. • Support the c

variable controls the maximum time that SQL optimization can wait for syn- chronously loading statistics before timeout. 33 Variable name Change type Description tidb_stats_load_pseudo_timeout �→ Newly added variable remains the same as before the upgrade. For the newly created TiDB clusters of v5.4.0 and later, this variable is ON by default. | | tidb_store_limit | Modified | Before v5.4.0, this variable can already cached for the corresponding query. The new binding does not affect execution plans cached before v5.4.0. • In v5.3 and earlier versions, TiDB Data Migration (DM) documentation is independent of

control) lock data when initializing the resolved- �→ ts. The default value is 2. 2.2.1.3 Others • Before the upgrade, check the value of the TiDB configuration feedback-probability �→ . If the value is replica of system tables, when building TiFlash replicas for each table, is no longer supported. Before upgrading the cluster, you need to clear the relevant system table replicas; otherwise, the upgrade more than 50%. #753 * Add a pre-check on the data to be imported and also on the target cluster before importing, and report errors to reject the import process if it does not meet the import requirements

2.2.1.5 Ease of use • Support a one-stop online data recovery when multiple replicas are lost Before TiDB v6.1.0, when multiple Region replicas are lost because of machine failure, users have to stop You can use the SHOW ANALYZE STATUS statement to show cluster-level statistics collec- tion tasks. Before TiDB v6.1.0, the SHOW ANALYZE STATUS statement shows instance- level tasks only, and history task from earlier versions, note that: * If the configuration items specified in the configuration file before the �→ upgrade already exist, TiDB will automatically update the values of �→ the configured items

observe a snapshot consistent with applying those writes in some order. Here, T3 implies T1 happened before T2, but T4 im- plies the opposite. We run an n-key generalization of these transactions continuously test uses appends of unique elements to lists. We include realtime dependencies (e.g. T1 com- pletes before T2 begins) in our analysis. TiDB doesn’t formally promise realtime guarantees, but our results hold adds new nodes before removing old ones, which should prevent scenarios where the num- ber of replicas falls below the configured target. In ad- dition, waiting for full replication before starting TiDB

increasingly crucial to quickly restore the clus- ter from failures to minimize business downtime. Before v7.6.0, the Region scattering algorithm is a primary bottleneck in performance restoration. In v7 statement varies in different TiDB versions before v7.6.0, so you might need to make additional ad- justments when using this statement. Specifically, before v4.0.0, LOAD DATA commits every 20000 rows. • Support dynamically modifying the size limit of a single row record in TiDB #49237 @zyguan Before v7.6.0, the size of a single row record in a transaction is limited by the TiDB configuration item

INDEX MERGE supports expressions connected by AND #39333 @guo-shaoge @time- and-fate @hailanwhu Before v6.5.0, TiDB only supported using index merge for the filter conditions con- nected by OR. Starting the log restore stage, the restore speed of one TiKV can reach 9 MiB/s, which is 50% faster than before. The restore speed is scalable and the RTO in DR scenarios is reduced greatly. The RPO in DR scenarios 88 • Fix the issue that data is replicated for multiple times when a new DM worker is scheduled before the existing worker exits #7658 @GMHDBJD • Fix the issue that DM precheck is not passed when the

pingcap.com/tidb/v7.5/sql-statement-import-into">IMPORT INTO (GA) Before v7.2.0, to import data based on the file system, you needed to �→ install 0 码力 | 6020 页 | 106.82 MB | 1 年前

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overhead of network transmission #7084 @solotzg The TiFlash MPP mode supports multiple Join algorithms. Before v7.1.0, TiDB de- termines whether the MPP mode uses the Broadcast Hash Join algorithm based on the disabled by default, indicating that the default algorithm selection method remains the same as that before v7.1.0. You can set the variable to ON to enable it. When it is enabled, you no longer need to manually as tidb_prepared_plan_cache_size, and tidb_enable_non_prepared_plan_cache �→ remains the setting before the upgrade. After sufficient performance testing, you can enable non-prepared plan cache using