TiDB 4.0.12 Release Notes

Release date: April 2, 2021

TiDB version: 4.0.12

New Features

• TiFlash

  • Add tools to check the status of tiflash replica for online rolling updates

Improvements

• TiDB

  • Refine the output information of the EXPLAIN statement for the batch cop mode #23164
  • Add the warning information for expressions that cannot be pushed to the storage layer in the output of the EXPLAIN statement #23020
  • Migrate a part of the DDL package code from Execute/ExecRestricted to the safe API (2) #22935
  • Migrate a part of the DDL package code from Execute/ExecRestricted to the safe API (1) #22929
  • Add optimization-time and wait-TS-time into the slow log #22918
  • Support querying partition_id from the infoschema.partitions table #22489
  • Add last_plan_from_binding to help the users know whether a SQL statement's execution plan is matched with the hints in the binding #21430
  • Scatter truncated tables without the pre-split option #22872
  • Add three format specifiers for the str_to_date expression #22812
  • Record the PREPARE execution failure as Failed Query OPM in the metrics monitor #22672
  • Do not report errors for the PREPARE execution if tidb_snapshot is set #22641

• TiKV

  • Prevent a large number of reconnections in a short period of time #9879
  • Optimize the write operations and Batch Get in the scenarios of many tombstones #9729
  • Change the default value of leader-transfer-max-log-lag to 128 to increase the success rate of leader transfer #9605

• PD

  • Update the Region cache only when pending-peers or down-peers changes, which reduces the pressure of updating heartbeats #3471
  • Prevent the Regions in split-cache from becoming the target of merge #3459

• TiFlash

  • Optimize the configuration file and remove useless items
  • Reduce the size of TiFlash binary files
  • Use an adaptive aggressive GC strategy to reduce memory usage

• Tools

  • TiCDC

    • Add a double confirmation when users create or resume the changefeed with the start-ts or checkpoint-ts 1 day before the current timestamp #1497
    • Add Grafana panels for the Old Value feature #1571

  • Backup & Restore (BR)

    • Log the HTTP_PROXY and HTTPS_PROXY environmental variables #827
    • Improve the backup performance when there are many tables #745
    • Report errors if the service safe point check fails #826
    • Add the cluster_version and br_version information in backupmeta #803
    • Add retry for external storage errors to increase the success rate of backup #851
    • Reduce memory usage during backup #886

  • TiDB Lightning

    • Check the TiDB cluster version before running TiDB Lightning to avoid unexpected errors #787
    • Fail fast when TiDB Lightning meets the cancel error #867
    • Add tikv-importer.engine-mem-cache-size and tikv-importer.local-writer-mem-cache-size configuration items to balance between memory usage and performance #866
    • Run batch split region in parallel for TiDB Lightning's Local-backend to increase the import speed #868
    • When using TiDB Lightning to import data from a S3 storage, TiDB Lightning no longer requires the s3:ListBucket permission #919
    • When resuming from a checkpoint, TiDB Lightning keeps using the original engine #924

Bug Fixes

• TiDB

  • Fix the issue that the get variable expression goes wrong when the session variable is hexadecimal literals#23372
  • Fix the issue that wrong collation is used when creating the fast execution plan for the Enum or Set type #23292
  • Fix the possible wrong result of the nullif expression when it is used with is-null #23279
  • Fix the issue that the auto-analysis is triggered outside its time range #23219
  • Fix the issue that the CAST function might ignore errors for the point get plan #23211
  • Fix a bug that prevents SPM from taking effect when CurrentDB is empty #23209
  • Fix the issue of possible wrong table filters for the IndexMerge plan #23165
  • Fix the issue of unexpected NotNullFlag in the returning types of the NULL constant #23135
  • Fix a bug that collation might not be handled by the text type #23092
  • Fix the issue that the range partition might incorrectly handle the IN expression #23074
  • Fix the issue that after marking a TiKV store as tombstone, starting new TiKV stores with different StoreIDs with the same IP address and port keeps returning the StoreNotMatch error #23071
  • Do not adjust the INT type when it is NULL and compared with YEAR #22844
  • Fix the issue of lost connection when loading data on tables with the auto_random column #22736
  • Fix the issue of DDL hangover when the DDL operation meets panic in the cancelling path #23297
  • Fix the wrong key range of index scan when comparing the YEAR column with NULL #23104
  • Fix the issue that a successfully created view is failed to use #23083

• TiKV

  • Fix the issue that the IN expression does not properly handle unsigned/signed integers #9850
  • Fix the issue that the ingest operation is not re-entrant #9779
  • Fix the issue that the space is missed when converting JSON to string in TiKV coprocessor #9666

• PD

  • Fix a bug that the isolation level is wrong when the store lacks the label #3474

• TiFlash

  • Fix the issue of incorrect execution results when the default value of the binary type column contains leading or tailing zero bytes
  • Fix a bug that TiFlash fails to synchronize schema if the name of the database contains special characters
  • Fix the issue of incorrect results when handling the IN expression with decimal values
  • Fix a bug that the metric for the opened file count shown in Grafana is high
  • Fix a bug that TiFlash does not support the Timestamp literal
  • Fix the potential not responding issue while handling the FROM_UNIXTIME expression
  • Fix the issue of incorrect results when casting string as integer
  • Fix a bug that the like function might return wrong results

• Tools

  • TiCDC

    • Fix a disorder issue of the resolved ts event #1464
    • Fix a data loss issue caused by wrong table scheduling due to the network problem #1508
    • Fix a bug of untimely release of resources after a processor is stopped #1547
    • Fix a bug that the transaction counter is not correctly updated, which might cause database connection leak #1524
    • Fix the issue that multiple owners can co-exist when PD has jitter, which might lead to table missing #1540

  • Backup & Restore (BR)

    • Fix a bug that WalkDir for the s3 storage returns nil if the target path is bucket name #733
    • Fix a bug that the status port is not served with TLS #839

  • TiDB Lightning

    • Fix the error that TiKV Importer might ignore that the file has already existed #848
    • Fix a bug that the TiDB Lightning might use the wrong timestamp and read the wrong data #850
    • Fix a bug that TiDB Lightning's unexpected exit might cause damaged checkpoint file #889
    • Fix the issue of possible data error that occurs because the cancel error is ignored #874