All notable changes to this project will be documented in this file. See also Release Notes, TiKV Changelog and PD Changelog.
- Add system table
performance_schema.events_statements_summary_by_digest
to troubleshoot performance issues at SQL level - Add the
WHERE
clause in TiDB’sSHOW TABLE REGIONS
syntax - Add the
worker-count
andtxn-batch
configuration items in Reparo to control the recovery speed
- Support
Split
commands in batches and the emptySplit
command in TiKV to split Regions in batches - Support double linked list for RocksDB in TiKV to improve performance of reverse scan
- Add two perf tools -
iosnoop
andfuncslower
in TiDB Ansible to better diagnose the cluster state - Optimize the output of slow query logs in TiDB by deleting redundant fields
- Update the default value of
txn-local-latches.enable
tofalse
to disable the default behaviour of checking conflicts of local transactions in TiDB - Add the
tidb_txn_mode
system variable of global scope in TiDB and allow using pessimistic lock by default. Note that TiDB still adopts optimistic lock by default. - Replace the
Index_ids
field in TiDB slow query logs withIndex_names
to improve the usability of slow query logs - Add the
split-region-max-num
parameter in the TiDB configuration file to modify the maximum number of Regions allowed in theSPLIT TABLE
syntax - Return the
Out Of Memory Quota
error instead of disconnect links in TiDB when a SQL execution exceeds the memory limit - Disallow dropping the
AUTO INCREMENT
attribute of columns in TiDB to avoid misoperations. To drop this attribute, change thetidb_allow_remove_auto_inc
system * variable.
- Fix the issue in TiDB that the special syntax
PRE_SPLIT_REGIONS
does not replicate data to the downstream by using notes - Fix the issue in TiDB that the slow query logs are incorrect when getting the result of
PREPARE
+EXECUTE
by using the cursor - Fix the issue in PD that adjacent small Regions cannot be merged
- Fix the issue that too many file descriptors are opened in idle clusters
- Fix the issue that
Our thanks go to the following contributors from the community for helping this release:
- Fix the issue that invalid query ranges might be resulted when splitted by feedback #12170
- Display the returned error of the
SHOW STATS_BUCKETS
statement in hexadecimal when the result contains invalid Keys #12094 - Fix the issue that when a query contains the
SLEEP
function (for example,select 1 from (select sleep(1)) t;)
), column pruning causes invalidsleep(1)
during query #11953 - Use index scan to lower IO when a query only concerns the number of columns rather than the table data #12112
- Do not use any index when no index is specified in
use index()
to becompatible with MySQL #12100 - Strictly limit the number of
TopN
records in theCMSketch
statistics to fix the issue that theANALYZE
statement fails because the statement count exceeds TiDB’s limit on the size of a transaction #11914 - Fix the error occurred when converting the subqueries contained in the
Update
statement #12483 - Optimize execution performance of the
select ... limit ... offset ...
statement by pushing the Limit operator down to theIndexLookUpReader
execution logic #12378
- Print the SQL statement in the log when the
PREPARED
statement is incorrectly executed #12191 - Support partition pruning when the
UNIX_TIMPESTAMP
function is used to implement partitioning #12169 - Fix the issue that no error is reported when
AUTO INCREMENT
incorrectly allocatesMAX int64
andMAX uint64
#12162 - Add the
WHERE
clause in theSHOW TABLE … REGIONS
andSHOW TABLE .. INDEX … REGIONS
syntaxes #12123 - Return the
Out Of Memory Quota
error instead of disconnect the link when a SQL execution exceeds the memory limit #12127 - Fix the issue that incorrect result is returned when
JSON_UNQUOTE
function handles JSON text #11955 - Fix the issue that
LAST INSERT ID
is incorrect when assigning values to theAUTO_INCREMENT
column in the first row (for example,insert into t (pk, c) values (1, 2), (NULL, 3)
) #12002 - Fix the issue that the
GROUPBY
parsing rule is incorrect in thePREPARE
statement #12351 - Fix the issue that the privilege check is incorrect in point queries #12340
- Fix the issue that the duration by sql_type for the
PREPARE
statement is not shown in the monitoring record #12331 - Support using aliases for tables in the point queries (for example,
select * from t tmp where a = "aa"
) #12282 - Fix the error occurred when not handling negative values as unsigned when inserting negative numbers into BIT type columns #12423
- Fix the incorrectly rounding of time (for example,
2019-09-11 11:17:47.999999666
should be rounded to2019-09-11 11:17:48
.) #12258 - Refine the usage of expression blacklist (for example,
<
is equivalent tolt
.) #11975 - Add the database prefix to the function name in the error message of non-existing functions (for example,
[expression:1305]FUNCTION test.std_samp does not exist
) #12111
- Add the
Prev_stmt
field in slow query logs to output the previous statement when the last statement isCOMMIT
#12180 - Optimize the output of slow query logs by deleting redundant fields #12144
- Modify the default value of
txn-local-latches.enable
tofalse
to disable the check for conflicts of local transactions in TiDB #12095 - Replace the
Index_ids
field in TiDB slow query logs withIndex_names
to improve the usability of slow query logs #12061 - Add the global system variable
tidb_txn_mode
in TiDB and allow using pessimistic lock by default #12049 - Add the
Backoff
field in the slow query logs to record the Backoff information in the commit phase of 2PC #12335 - Fix the issue that the slow query logs are incorrect when getting the result of
PREPARE
+EXECUTE
by using the cursor (for example,PREPARE stmt1FROM SELECT * FROM t WHERE a > ?; EXECUTE stmt1 USING @variable
) #12392 - Support
tidb_enable_stmt_summary
. When this feature is enabled, TiDB counts the SQL statements and the result can be queried by using the system tableperformance_schema.events_statements_summary_by_digest
. #12308 - Adjust the level of some logs in tikv-client (for example, change the log level of
batchRecvLoop fails
fromERROR
toINFO
) #12383
- Add the variable of
tidb_allow_remove_auto_inc
. Dropping theAUTO INCREMENT
attribute of the column is disabled by default #12145 - Fix the issue that the uncommented TiDB-specific syntax
PRE_SPLIT_REGIONS
might cause t errors in the downstream database during data replication #12120 - Add the
split-region-max-num
variable in the configuration file so that the maximum allowable number of Regions is adjustable #12097 - Support splitting a Region into multiple Regions and fix the timeout issue during Region scattering #12343
- Fix the issue that the
drop index
statement fails when the index that contains anauto_increment
column referenced byanother two indexes #12344
- Add the
connection_transient_failure_count
monitoring metric to count the number of gRPC connection errors intikvclient
#12093
- Add the
opt_rule_blacklist
table to disable logic optimization rules such asaggregation_eliminate
andcolumn_prune
#11658 - Fix the issue that incorrect results might be returned for
Index Join
when the join key uses a prefix index or an unsigned index column that is equal to a negative value #11759 - Fix the issue that
"
or\
in theSELECT
statements ofcreate ... binding ...
might result in parsing errors #11726
- Fix the issue that type errors in the return value might occur when the
Quote
function handles a null value #11619 - Fix the issue that incorrect results for
Ifnull
might be returned whenMax
/min
is used for type inferring withNotNullFlag
retained #11641 - Fix the potential error that occurs when comparing bit type data in string form #11660
- Decrease the concurrency for data that requires sequential read to reduce the possibility of OOM #11679
- Fix the issue that incorrect type inferring might be caused when multiple parameters are unsigned for some built-in functions (e.g.
If
,Coalesce
) #11621 - Fix the incompatibility with MySQL when the
Div
function handles unsigned decimal types #11813 - Fix the issue that panic might occur when executing SQL statements that modify the status of Pump/Drainer #11827
- Fix the issue that panic might occur for
select ... for update
when Autocommit = 1 and there is nobegin
statement #11736 - Fix the permission check error that might occur when the
set default role
statement is executed #11777 - Fix the permission check error that might occur when
create user
ordrop user
is executed #11814 - Fix the issue that the
select ... for update
statement might auto retry when it is constructed into thePointGetExecutor
function #11718 - Fix the boundary error that might occur when the Window function handles partition #11825
- Fix the issue that the
Time
function hits EOF errors when handling an incorrectly formatted argument #11893 - Fix the issue that the Window function does not check the passed-in parameters #11705
- Fix the issue that the plan result viewed via
Explain
is inconsistent with the actually executed plan #11186 - Fix the issue that duplicate memory referenced by the Window function might result in a crash or incorrect results #11823
- Update the incorrect information in the
Succ
field in the slow log #11887
- Rename the
tidb_back_off_wexight
variable totidb_backoff_weight
#11665 - Update the minimum TiKV version compatible with the current TiDB to v3.0.0 #11618
- Support
make testSuite
to ensure the suites in the test are correctly used #11685
- Skip the execution of unsupported partition-related DDL statements, including statements that modify the partition type while deleting multiple partitions #11373
- Disallow a Generated Column to be placed before its dependent columns #11686
- Modify the default values of
tidb_ddl_reorg_worker_cnt
andtidb_ddl_reorg_batch_size
#11874
- Add new backoff monitoring types to record duration for each backoff type; add more backoff metrics to cover previously uncounted types such as commit backoff #11728
- Fix the issue that the "Can't find column in schema" message is reported when the same table occurs multiple times in a query and logically the query result is always empty #11247
- Fix the issue that the query plan does not meet the expectation caused by the
TIDB_INLJ
hint not working correctly in some cases (likeexplain select /*+ TIDB_INLJ(t1) */ t1.b, t2.a from t t1, t t2 where t1.b = t2.a
) #11362 - Fix the issue that the column name in the query result is wrong in some cases (like
SELECT IF(1,c,c) FROM t
) #11379 - Fix the issue that some queries like
SELECT 0 LIKE 'a string'
returnTRUE
becausetheLIKE
expression is implicitly converted to 0 in some cases #11411 - Support sub-queries in the
SHOW
statement, likeSHOW COLUMNS FROM tbl WHERE FIELDS IN (SELECT 'a')
#11459 - Fix the issue that the related column of the aggregate function cannot be found and an error is reported caused by the
outerJoinElimination
optimizing rule not correctly handling the column alias; improve alias parsing in the optimizing process to make optimization cover more query types #11377 - Fix the issue that no error is reported when the syntax restriction is violated in the Window function (for example,
UNBOUNDED PRECEDING
is not allowed to appear at the end of the Frame definition) #11543 - Fix the issue that
FUNCTION_NAME
is in uppercase in theERROR 3593 (HY000): You cannot use the window function FUNCTION_NAME in this context
error message, which causes incompatibility with MySQL #11535 - Fix the issue that the unimplemented
IGNORE NULLS
syntax in the Window function is used but no error is reported #11593 - Fix the issue that the Optimizer does not correctly estimate time equal conditions #11512
- Support updating the Top-N statistics based on the feedback information #11507
- Fix the issue that the returned value is not
NULL
when theINSERT
function containsNULL
in parameters #11248 - Fix the issue that the computing result might be wrong when the partitioned table is checked by the
ADMIN CHECKSUM
operation #11266 - Fix the issue that the result might be wrong when INDEX JOIN uses the prefix index #11246
- Fix the issue that result might be wrong caused by incorrectly aligning fractions when the
DATE_ADD
function does subtraction on date numbers involving microseconds #11288 - Fix the wrong result caused by the
DATE_ADD
function incorrectly processing the negative numbers inINTERVAL
#11325 - Fix the issue that the number of fractional digits returned by
Mod
(%
),Multiple
(*
) orMinus
(-
) is different from that in MySQL whenMod
,Multiple
orMinus
returns 0 and the number of fractional digits is large (likeselect 0.000 % 0.11234500000000000000
) #11251 - Fix the issue that
NULL
with a warning is incorrectly returned when the length of the result returned byCONCAT
andCONCAT_WS
functions exceedsmax_allowed_packet
#11275 - Fix the issue that
NULL
with a warning is incorrectly returned when parameters in theSUBTIME
andADDTIME
functions are invalid #11337 - Fix the issue that
NULL
is incorrectly returned when parameters in theCONVERT_TZ
function are invalid #11359 - Add the
MEMORY
column to the result returned byEXPLAIN ANALYZE
to show the memory usage of this query #11418 - Add
CARTESIAN JOIN
to the result ofEXPLAIN
#11429 - Fix the incorrect data of auto-increment columns of the float and double types #11385
- Fix the panic issue caused by some
nil
information when pseudo statistics are dumped #11460 - Fix the incorrect query result of
SELECT … CASE WHEN … ELSE NULL ...
caused by constant folding optimization #11441 - Fix the issue that
floatStrToIntStr
does not correctly parse the input such as+999.9999e2
#11473 - Fix the issue that
NULL
is not returned in some cases when the result of theDATE_ADD
andDATE_SUB
function overflows #11476 - Fix the issue that the conversion result is different from that in MySQL if the string contains an invalid character when a long string is converted to an integer #11469
- Fix the issue that the result of the
REGEXP BINARY
function is incompatible with MySQL caused by case sensitiveness of this function #11504 - Fix the issue that an error is reported when the
GRANT ROLE
statement receivesCURRENT_ROLE
; fix the issue that theREVOKE ROLE
statement does not correctly revoke themysql.default_role
privilege #11356 - Fix the display format issue of the
Incorrect datetime value
warning information when executing statements likeSELECT ADDDATE('2008-01-34', -1)
#11447 - Fix the issue that the error message reports
constant … overflows float
rather thanconstant … overflows bigint
if the result overflows when a float field of the JSON data is converted to an integer #11534 - Fix the issue that the result might be wrong caused by incorrect type conversion when the
DATE_ADD
function receivesFLOAT
,DOUBLE
andDECIMAL
column parameters #11527 - Fix the wrong result caused by incorrectly processing the sign of the INTERVAL fraction in the
DATE_ADD
function #11615 - Fix the incorrect query result when Index Lookup Join contains the prefix index caused by
Ranger
not correctly handling the prefix index #11565 - Fix the issue that the "Incorrect arguments to NAME_CONST" message is reported if the
NAME_CONST
function is executed when the second parameter ofNAME_CONST
is a negative number #11268 - Fix the issue that the result is incompatible with MySQL when an SQL statement involves computing the current time and the value is fetched multiple times; use the same value when fetching the current time for the same SQL statement #11394
- Fix the issue that
Close
is not called for ChildExecutor when theClose
of baseExecutor reports an error. This issue might lead to Goroutine leaks when theKILL
statements do not take effect and ChildExecutor is not closed #11576
- Fix the issue that the auto-added value is 0 instead of the current timestamp when
LOAD DATA
processes the missingTIMESTAMP
field in the CSV file #11250 - Fix issues that the
SHOW CREATE USER
statement does not correctly check related privileges, andUSER
andHOST
returned bySHOW CREATE USER CURRENT_USER()
might be wrong #11229 - Fix the issue that the returned result might be wrong when
executeBatch
is used in JDBC #11290 - Reduce printing the log information of the streaming client when changing the TiKV server's port #11370
- Optimize the logic of reconnecting the streaming client to the TiKV server so that the streaming client will not be blocked for a long time #11372
- Add
REGION_ID
inINFORMATION_SCHEMA.TIDB_HOT_REGIONS
#11350 - Cancel the timeout duration of obtaining Region information from the PD API to ensure that obtaining Region information will not end in a failure when TiDB API http://{TiDBIP}:10080/regions/hot is called due to PD timeout when the number of Regions is large #11383
- Fix the issue that Region related requests do not return partitioned table-related Regions in the HTTP API #11466
- Modify some default parameters related to pessimistic locks, these modifications reduce the probability of locking timeout caused by slow operations when the user manually validates pessimistic locking #11521
- Increase the default TTL of pessimistic locking from 30 seconds to 40 seconds
- Increase the maximum TTL from 60 seconds to 120 seconds
- Calculate the pessimistic locking duration from the first
LockKeys
request
- Change the
SendRequest
function logic in the TiKV client: try to immediately connect to another peer instead of keeping waiting when the connect cannot be built #11531 - Optimize the Region cache: label the removed store as invalid when a store is moved while another store goes online with a same address, to update the store information in the cache as soon as possible #11567
- Add the Region ID to the result returned by the
http://{TiDB_ADDRESS:TIDB_IP}/mvcc/key/{db}/{table}/{handle}
API #11557 - Fix the issue that Scatter Table does not work caused by the Scatter Table API not escaping the Range key #11298
- Optimize the Region cache: label the store where the Region exists as invalid when the correspondent store is inaccessible to avoid reduced query performance caused by accessing this store #11498
- Fix the error that the table schema can still be obtained through the HTTP API after dropping the database with the same name multiple times #11585
- Fix the issue that an error occurs when a non-string column with a zero length is being indexed #11214
- Disallow modifying the columns with foreign key constraints and full-text indexes (Note: TiDB still supports foreign key constraints and full-text indexes in syntax only) #11274
- Fix the issue that the index offset of the column might be wrong because the position changed by the
ALTER TABLE
statement and the default value of the column are used concurrently #11346 - Fix two issues that occur when parsing JSON files:
- Disallow dropping indexes on the auto-increment column to avoid that the auto-increment column might get an incorrect result #11399
- Fix the following issues #11492:
- The character set and the collation of the column are not consistent when explicitly specifying the collation but not the character set
- The error is not correctly reported when there is a conflict between the character set and the collation that are specified by
ALTER TABLE … MODIFY COLUMN
- Incompatibility with MySQL when using
ALTER TABLE … MODIFY COLUMN
to specify character sets and collations multiple times
- Add the trace details of the subquery to the result of the
TRACE
query #11458 - Optimize the performance of executing
ADMIN CHECK TABLE
and greatly reduce its execution time #11547 - Add the result returned by
SPLIT TABLE … REGIONS/INDEX
and makeTOTAL_SPLIT_REGION
andSCATTER_FINISH_RATIO
display the number of Regions that have been split successfully before timeout in the result #11484 - Fix the issue that the precision displayed by statements like
SHOW CREATE TABLE
is incomplete whenON UPDATE CURRENT_TIMESTAMP
is the column attribute and the float precision is specified #11591 - Fix the issue that the index result of the column cannot be correctly calculated when the expression of a virtual generated column contains another virtual generated column #11475
- Fix the issue that the minus sign cannot be added after
VALUE LESS THAN
in theALTER TABLE … ADD PARTITION …
statement #11581
- Fix the issue that data is not collected and reported because the
TiKVTxnCmdCounter
monitoring metric is not registered #11316 - Add the
BindUsageCounter
,BindTotalGauge
andBindMemoryUsage
monitoring metrics for the Bind Info #11467
- Add the
tidb_wait_split_region_finish_backoff
session variable to control the backoff time of splitting Regions #11166 - Support automatically adjusting the auto-incremental ID allocation step based on the load, and the auto-adjustment scope of the step is 1000~2000000 #11006
- Add the
ADMIN PLUGINS ENABLE
/ADMIN PLUGINS DISABLE
SQL statement to dynamically enable or disable plugins #11157 - Add the session connection information in the audit plugin #11013
- Add optimizer hint
MAX_EXECUTION_TIME
, which places a limit N (a timeout value in milliseconds) on how long aSELECT
statement is permitted to execute before the server terminates it: #11026 - Change the default behavior during the period of splitting Regions to wait for PD to finish scheduling #11166
- Prohibit Window Functions from being cached in Prepare Plan Cache to avoid incorrect results in some cases #11048
- Prohibit
ALTER
statements from modifying the definition of stored generated columns #11068 - Disallow changing virtual generated columns to stored generated columns #11068
- Disallow changing the generated column expression with indexes #11068
- Support compiling TiDB on the ARM64 architecture #11150
- Support modifying the collation of a database or a table, but the character set of the database/table has to be UTF-8 or utf8mb4 #11086
- Fix the issue that an error is reported when the
SELECT
subquery in theUPDATE … SELECT
statement fails to resolve the column in theUPDATE
expression #11252 - Fix the panic issue that happens when a column is queried on multiple times and the returned result is NULL during point queries #11226
- Fix the data race issue caused by non-thread safe
rand.Rand
when using theRAND
function #11169 - Fix the bug that the memory usage of a SQL statement exceeds the threshold but the execution of this statement is not canceled in some cases when
oom-action="cancel"
is configured #11004 - Fix the issue that when a query ends,
SHOW PROCESSLIST
shows that the memory usage is not0
because the memory usage of MemTracker was not correctly cleaned #10970 - Fix the bug that the result of comparing integers and non-integers is not correct in some cases #11194
- Fix the bug that the query result is not correct when the query on table partitions contains a predicate in explicit transactions #11196
- Fix the DDL job panic issue because
infoHandle
might beNULL
#11022 - Fix the issue that the query result is not correct because the queried column is not referenced in the subquery and is then wrongly pruned when running a nested aggregation query #11020
- Fix the issue that the
Sleep
function does not respond to theKILL
statement in time #11028 - Fix the issue that the
DB
andINFO
columns shown by theSHOW PROCESSLIST
command are incompatible with MySQL #11003 - Fix the system panic issue caused by the
FLUSH PRIVILEGES
statement whenskip-grant-table=true
is configured #11027 - Fix the issue that the primary key statistics collected by
FAST ANALYZE
are not correct when the table primary key is anUNSIGNED
integer #11099 - Fix the issue that the "invalid key" error is reported by the
FAST ANALYZE
statement in some cases #11098 - Fix the issue that the precision shown by the
SHOW CREATE TABLE
statement is incomplete whenCURRENT_TIMESTAMP
is used as the default value of the column and the decimal precision is specified #11088 - Fix the issue that the function name is not in lowercase when window functions report an error to make it compatible with MySQL #11118
- Fix the issue that TiDB fails to connect to TiKV and thus cannot provide service after the background thread of TiKV Client Batch gRPC panics #11101
- Fix the issue that the variable is set incorrectly by
SetVar
because of the shallow copy of the string #11044 - Fix the issue that the execution fails and an error is reported when the
INSERT … ON DUPLICATE
statement is applied on table partitions #11231 - Pessimistic locking (experimental feature)
- Fix the issue that an incorrect result is returned because of the invalid lock on the row when point queries are run using the pessimistic locking and the returned data is empty #10976
- Fix the issue that the query result is not correct because
SELECT … FOR UPDATE
does not use the correct TSO when using the pessimistic locking in the query #11015
- Change the detection behavior from immediate conflict detection to waiting when an optimistic transaction meets a pessimistic lock to avoid worsening the lock conflict #11051
- Fix wrong query results caused by column pruning in some cases #11019
- Fix the wrongly displayed information in
db
andinfo
columns ofshow processlist
#11000 - Fix the issue that
MAX_EXECUTION_TIME
as a SQL hint and global variable does not work in some cases #10999 - Support automatically adjust the incremental step allocated by auto-increment ID based on the load #10997
- Fix the issue that the
Distsql
memory information ofMemTracker
is not correctly cleaned when a query ends #10971 - Add the
MEM
column in theinformation_schema.processlist
table to describe the memory usage of a query #10896 - Add the
max_execution_time
global system variable to control the maximum execution time of a query #10940 - Fix the panic caused by using unsupported aggregate functions #10911
- Add an automatic rollback feature for the last transaction when the
load data
statement fails #10862 - Fix the issue that TiDB returns a wrong result in some cases when the
OOMAction
configuration item is set toCancel
#11016 - Disable the
TRACE
statement to avoid the TiDB panic issue #11039 - Add the
mysql.expr_pushdown_blacklist
system table that dynamically enables/disables pushing down specific functions to Coprocessor #10998 - Fix the issue that the
ANY_VALUE
function does not work in theONLY_FULL_GROUP_BY
mode #10994 - Fix the incorrect evaluation caused by not doing a deep copy when evaluating the user variable of the string type #11043
- Support Window Functions; compatible with all window functions in MySQL 8.0, including
NTILE
,LEAD
,LAG
,PERCENT_RANK
,NTH_VALUE
,CUME_DIST
,FIRST_VALUE
,LAST_VALUE
,RANK
,DENSE_RANK
, andROW_NUMBER
- Support Views (Experimental)
- Improve Table Partition
- Support Range Partition
- Support Hash Partition
- Add the plug-in framework, supporting plugins such as IP Whitelist (Enterprise feature) and Audit Log (Enterprise feature).
- Support the SQL Plan Management function to create SQL execution plan binding to ensure query stability (Experimental)
- Optimize the
NOT EXISTS
subquery and convert it toAnti Semi Join
to improve performance - Optimize the constant propagation on the
Outer Join
, and add the optimization rule ofOuter Join
elimination to reduce non-effective computations and improve performance - Optimize the
IN
subquery to executeInner Join
after aggregation to improve performance - Optimize
Index Join
to adapt to more scenarios - Improve the Partition Pruning optimization rule of Range Partition
- Optimize the query logic for
_tidb_rowid
to avoid full table scan and improve performance - Match more prefix columns of the indexes when extracting access conditions of composite indexes if there are relevant columns in the filter to improve performance
- Improve the accuracy of cost estimates by using order correlation between columns
- Optimize
Join Reorder
based on the Greedy algorithm and the dynamic planning algorithm to improve accuracy for index selection usingJoin
- Support Skyline Pruning, with some rules to prevent the execution plan from relying too heavily on statistics to improve query stability
- Improve the accuracy of row count estimation for single-column indexes with NULL values
- Support
FAST ANALYZE
that randomly samples in each Region to avoid full table scan and improve performance with statistics collection - Support the incremental Analyze operation on monotonically increasing index columns to improve performance with statistics collection
- Support using subqueries in the
DO
statement - Support using
Index Join
in transactions - Optimize
prepare
/execute
to support DDL statements with no parameters - Modify the system behaviour to auto load statistics when the
stats-lease
variable value is 0 - Support exporting historical statistics
- Support the
dump
/load
correlation of histograms
- Optimize log output:
EXECUTE
outputs user variables andCOMMIT
outputs slow query logs to facilitate troubleshooting - Support the
EXPLAIN ANALYZE
function to improve SQL tuning usability - Support the
admin show next_row_id
command to get the ID of the next row - Add six built-in functions:
JSON_QUOTE
,JSON_ARRAY_APPEND
,JSON_MERGE_PRESERVE
,BENCHMARK
,COALESCE
, andNAME_CONST
- Optimize control logics on the chunk size to dynamically adjust based on the query context, to reduce the SQL execution time and resource consumption
- Support tracking and controlling memory usage in three operators -
TableReader
,IndexReader
andIndexLookupReader
- Optimize the Merge Join operator to support an empty
ON
condition - Optimize write performance for single tables that contains too many columns
- Improve the performance of
admin show ddl jobs
by supporting scanning data in reverse order - Add the
split table region
statement to manually split the table Region to alleviate the hotspot issue - Add the
split index region
statement to manually split the index Region to alleviate the hotspot issue - Add a blacklist to prohibit pushing down expressions to Coprocessor
- Optimize the
Expensive Query
log to print the SQL query in the log when it exceeds the configured limit of execution time or memory
- Support migrating from character set
utf8
toutf8mb4
- Change the default character set from
utf8
toutf8mb4
- Add the
alter schema
statement to modify the character set and the collation of the database - Support ALTER algorithm
INPLACE
/INSTANT
- Support
SHOW CREATE VIEW
- Support
SHOW CREATE USER
- Support fast recovery of mistakenly deleted tables
- Support adjusting the number of concurrencies of ADD INDEX dynamically
- Add the
pre_split_regions
option that pre-allocates Regions when creating the table using theCREATE TABLE
statement, to relieve write hot Regions caused by lots of writes after the table creation - Support splitting Regions by the index and range of the table specified using SQL statements to relieve hotspot issues
- Add the
ddl_error_count_limit
global variable to limit the number of DDL task retries - Add a feature to use
SHARD_ROW_ID_BITS
to scatter row IDs when the column contains an AUTO_INCREMENT attribute to relieve the hotspot issue - Optimize the lifetime of invalid DDL metadata to speed up recovering the normal execution of DDL operations after upgrading the TiDB cluster
- Support the pessimistic transaction model (Experimental)
- Optimize transaction processing logics to adapt to more scenarios:
- Change the default value
tidb_disable_txn_auto_retry
toon
, which means non-auto committed transactions will not be retried - Add the
tidb_batch_commit
system variable to split a transaction into multiple ones to be executed concurrently - Add the
tidb_low_resolution_tso
system variable to control the number of TSOs to obtain in batches and reduce the number of times that transactions request for TSOs, to improve performance in scenarios with relatively low requirement of consistency - Add the
tidb_skip_isolation_level_check
variable to control whether to report errors when the isolation level is set to SERIALIZABLE - Modify the
tidb_disable_txn_auto_retry
system variable to make it work on all retryable errors
- Change the default value
- Perform permission check on the
ANALYZE
,USE
,SET GLOBAL
, andSHOW PROCESSLIST
statements - Support Role Based Access Control (RBAC) (Experimental)
- Optimize slow query logs
- Restructure the log format
- Optimize the log content
- Optimize the log query method to support using the
INFORMATION_SCHEMA.SLOW_QUERY
andADMIN SHOW SLOW
statements of the memory table to query slow query logs
- Develop a unified log format specification with restructured log system to facilitate collection and analysis by tools
- Support using SQL statements to manage Binlog services, including querying status, enabling Binlog, maintaining and sending Binlog strategies.
- Support using
unix_socket
to connect to the database - Support
Trace
for SQL statements - Support getting information for a TiDB instance via the
/debug/zip
HTTP interface to facilitate troubleshooting. - Optimize monitoring items to facilitate troubleshooting:
- Add the
high_error_rate_feedback_total
monitoring item to monitor the difference between the actual data volume and the estimated data volume based on statistics - Add a QPS monitoring item in the database dimension
- Add the
- Optimize the system initialization process to only allow the DDL owner to perform the initialization. This reduces the startup time for initialization or upgrading.
- Optimize the execution logic of
kill query
to improve performance and ensure resource is release properly - Add a startup option
config-check
to check the validity of the configuration file - Add the
tidb_back_off_weight
system variable to control the backoff time of internal error retries - Add the
wait_timeout
andinteractive_timeout
system variables to control the maximum idle connections allowed - Add the connection pool for TiKV to shorten the connection establishing time
- Support the
ALLOW_INVALID_DATES
SQL mode - Support the MySQL 320 Handshake protocol
- Support manifesting unsigned BIGINT columns as auto-increment columns
- Support the
SHOW CREATE DATABASE IF NOT EXISTS
syntax - Optimize the fault tolerance of
load data
for CSV files - Abandon the predicate pushdown operation when the filtering condition contains a user variable to improve the compatibility with MySQL's behavior of using user variables to simulate Window Functions
- Remove the feature of collecting virtual generated column statistics#10629
- Fix the issue that the primary key constant overflows during point queries #10699
- Fix the issue that using uninitialized information in
fast analyze
causes panic #10691 - Fix the issue that executing the
create view
statement usingprepare
causes panic because of wrong column information #10713 - Fix the issue that the column information is not cloned when handling window functions #10720
- Fix the wrong estimation for the selectivity rate of the inner table selection in index join #10854
- Support automatic loading statistics when the
stats-lease
variable value is 0 #10811
- Fix the issue that resources are not correctly released when calling the
Close
function inStreamAggExec
#10636 - Fix the issue that the order of
table_option
andpartition_options
is incorrect in the result of executing theshow create table
statement for partitioned tables #10689 - Improve the performance of
admin show ddl jobs
by supporting scanning data in reverse order #10687 - Fix the issue that the result of the
show grants
statement in RBAC is incompatible with that of MySQL when this statement has thecurrent_user
field #10684 - Fix the issue that UUIDs might generate duplicate values on multiple nodes #10712
- Fix the issue that the
show view
privilege is not considered inexplain
#10635 - Add the
split table region
statement to manually split the table Region to alleviate the hotspot issue #10765 - Add the
split index region
statement to manually split the index Region to alleviate the hotspot issue #10764 - Fix the incorrect execution issue when you execute multiple statements such as
create user
,grant
, orrevoke
consecutively #10737 - Add a blacklist to prohibit pushing down expressions to Coprocessor #10791
- Add the feature of printing the
expensive query
log when a query exceeds the memory configuration limit #10849 - Add the
bind-info-lease
configuration item to control the update time of the modified binding execution plan #10727 - Fix the OOM issue in high concurrent scenarios caused by the failure to quickly release Coprocessor resources, resulted from the
execdetails.ExecDetails
pointer #10832 - Fix the panic issue caused by the
kill
statement in some cases #10876
- Fix the issue that goroutine might leak when repairing GC #10683
- Support displaying the
host
information in slow queries #10693 - Support reusing idle links that interact with TiKV #10632
- Fix the support for enabling the
skip-grant-table
option in RBAC #10738 - Fix the issue that
pessimistic-txn
configuration goes invalid #10825 - Fix the issue that the actively cancelled ticlient requests are still retried #10850
- Improve performance in the case where pessimistic transactions conflict with optimistic transactions #10881
- Fix the issue that modifying charset using
alter table
causes theblob
type change #10698 - Add a feature to use
SHARD_ROW_ID_BITS
to scatter row IDs when the column contains anAUTO_INCREMENT
attribute to alleviate the hotspot issue #10794 - Prohibit adding stored generated columns by using the
alter table
statement #10808 - Optimize the invalid survival time of DDL metadata to shorten the period during which the DDL operation is slower after cluster upgrade #10795
- Add a feature to use
SHARD_ROW_ID_BITS
to scatter row IDs when the column contains anAUTO_INCREMENT
attribute to relieve the hotspot issue #10788 - Optimize the lifetime of invalid DDL metadata to speed up recovering the normal execution of DDL operations after upgrading the TiDB cluster #10789
- Fix the OOM issue in high concurrent scenarios caused by the failure to quickly release Coprocessor resources, resulted from the
execdetails.ExecDetails
pointer #10833 - Add the
update-stats
configuration item to control whether to update statistics #10772 - Add the following TiDB-specific syntax to support Region presplit to solve the hotspot issue:
- Fix the panic issue caused by the
KILL
syntax in some cases #10879 - Improve the compatibility with MySQL for
ADD_DATE
in some cases #10718 - Fix the wrong estimation for the selectivity rate of the inner table selection in index join #10856
- Fix the issue caused by unmatched data types when using the index query feedback #10755
- Fix the issue that the blob column is changed to the text column caused by charset altering in some cases #10745
- Fix the issue that the
GRANT
operation in the transaction mistakenly reports “Duplicate Entry” in some cases #10739 - Improve the compatibility with MySQL of the following features
- Change the column charset while changing the table charset #10714
- Fix the overflow issue when converting a decimal to a float in some cases #10730
- Fix the issue that some extremely large messages report the “grpc: received message larger than max” error caused by inconsistent maximum sizes of messages sent/received by gRPC of TiDB and TiKV #10710
- Fix the panic issue caused by
ORDER BY
not filtering NULL in some cases #10488 - Fix the issue that values returned by the
UUID
function might be duplicate when multiple nodes exist #10711 - Change the value returned by
CAST(-num as datetime)
fromerror
to NULL #10703 - Fix the issue that an unsigned histogram meets signed ranges in some cases #10695
- Fix the issue that an error is reported mistakenly for reading data when the statistics feedback meets the bigint unsigned primary key #10307
- Fix the issue that the result of
Show Create Table
for partitioned tables is not correctly displayed in some cases #10690 - Fix the issue that the calculation result of the
GROUP_CONCAT
aggregate function is not correct for some correlated subqueries #10670 - Fix the issue that the result of
Show Create Table
for partitioned tables is not correctly displayed in some cases #10690
- Fix the issue that incorrect schema is used for
delete from join
#10595 - Fix the issue that the built-in
CONVERT()
may return incorrect field type #10263 - Merge non-overlapped feedback when updating bucket count #10569
- Fix calculation errors of
unix_timestamp()-unix_timestamp(now())
#10491 - Fix the incompatibility issue of
period_diff
with MySQL 8.0 #10501 - Skip
Virtual Column
when collecting statistics to avoid exceptions #10628 - Support the
SHOW OPEN TABLES
statement #10374 - Fix the issue that goroutine leak may happen in some cases #10656
- Fix the issue that setting the
tidb_snapshot
variable in some cases may cause incorrect parsing of time format #10637
- Support Index Join in more scenarios #10540
- Support exporting historical statistics #10291
- Support the incremental
Analyze
operation on monotonically increasing index columns #10355 - Neglect the NULL value in the
Order By
clause #10488 - Fix the wrong schema information calculation of the
UnionAll
logical operator when simplifying the column information #10384 - Avoid modifying the original expression when pushing down the
Not
operator #10363 - Support the
dump
/load
correlation of histograms #10573
- Handle virtual columns with a unique index properly when fetching duplicate rows in
batchChecker
#10370 - Fix the scanning range calculation issue for the
CHAR
column #10124 - Fix the issue of
PointGet
incorrectly processing negative numbers #10113 - Merge
Window
functions with the same name to improve execution efficiency #9866 - Allow the
RANGE
frame in aWindow
function to contain noOrderBy
clause #10496
Fix the issue that TiDB continuously creates a new connection to TiKV when a fault occurs in TiKV #10301
Make tidb_disable_txn_auto_retry
affect all retryable errors instead of only write conflict errors #10339
Allow DDL statements without parameters to be executed using prepare
/execute
#10144
Add the tidb_back_off_weight
variable to control the backoff time #10266
Prohibit TiDB retrying non-automatically committed transactions in default conditions by setting the default value of tidb_disable_txn_auto_retry
to on
#10266
Fix the database privilege judgment of role
in RBAC
#10261
Support the pessimistic transaction model (experimental) #10297
Reduce the wait time for handling lock conflicts in some cases #10006
Make the Region cache able to visit follower nodes when a fault occurs in the leader node #10256
Add the tidb_low_resolution_tso
variable to control the number of TSOs obtained in batches and reduce the times of transactions obtaining TSO to adapt for scenarios where data consistency is not so strictly required #10428
Fix the uppercase issue of the charset name in the storage of the old version of TiDB
#10272
Support preSplit
of table partition, which pre-allocates table Regions when creating a table to avoid write hotspots after the table is created
#10221
Fix the issue that TiDB incorrectly updates the version information in PD in some cases #10324
Support modifying the charset and collation using the ALTER DATABASE
statement
#10393
Support splitting Regions based on the index and range of the specified table to relieve hotspot issues
#10203
Prohibit modifying the precision of the decimal column using the alter table
statement
#10433
Fix the restriction for expressions and functions in hash partition
#10273
Fix the issue that adding indexes in a table that contains partitions will in some cases cause TiDB panic
#10475
Validate table information before executing the DDL to avoid invalid table schemas
#10464
Enable hash partition by default; and enable range columns partition when there is only one column in the partition definition
#9936
- Fix the issue that some abnormalities cause incorrect table schema when using
tidb_snapshot
to read the history data #10359 - Fix the issue that the
NOT
function causes wrong read results in some cases #10363 - Fix the wrong behavior of
Generated Column
in theReplace
orInsert on duplicate update
statement #10385 - Fix a bug of the
BETWEEN
function in theDATE
/DATETIME
comparison #10407 - Fix the issue that a single line of a slow log that is too long causes an error report when using the
SLOW_QUERY
table to query a slow log #10412 - Fix the issue that the result of
DATETIME
plusINTERVAL
is not the same with that of MySQL in some cases #10416, #10418 - Add the check for the invalid time of February in a leap year #10417
- Execute the internal initialization operation limitation only in the DDL owner to avoid a large number of conflict error reports when initializing the cluster #10426
- Fix the issue that
DESC
is incompatible with MySQL when the default value of the output timestamp column isdefault current_timestamp on update current_timestamp
#10337 - Fix the issue that an error occurs during the privilege check in the
Update
statement #10439 - Fix the issue that wrong calculation of
RANGE
causes a wrong result in theCHAR
column in some cases #10455 - Fix the issue that the data might be overwritten after decreasing
SHARD_ROW_ID_BITS
#9868 - Fix the issue that
ORDER BY RAND()
does not return random numbers #10064 - Prohibit the
ALTER
statement modifying the precision of decimals #10458 - Fix the compatibility issue of the
TIME_FORMAT
function with MySQL #10474 - Check the parameter validity of
PERIOD_ADD
#10430 - Fix the issue that the behavior of the invalid
YEAR
string in TiDB is incompatible with that in MySQL #10493 - Support the
ALTER DATABASE
syntax #10503 - Fix the issue that the
SLOW_QUERY
memory engine reports an error when no;
exists in the slow query statement #10536 - Fix the issue that the
Add index
operation in partitioned tables cannot be canceled in some cases #10533 - Fix the issue that the OOM panic cannot be recovered in some cases #10545
- Improve the security of the DDL operation rewriting the table metadata #10547
- Improve the accuracy of cost estimates by using order correlation between columns; introduce a heuristic parameter
tidb_opt_correlation_exp_factor
to control the preference for index scans for scenarios when correlation cannot be directly used for estimation. #9839 - Match more prefix columns of the indexes when extracting access conditions of composite indexes if there are relevant columns in the filter #10053
- Use the dynamic programming algorithm to specify the execution order of join operations when the number of tables participating in the join is less than the value of
tidb_opt_join_reorder_threshold
. #8816 - Match more prefix columns of the indexes in the inner tables that build the index join when using composite indexes as the access conditions #8471
- Improve the accuracy of row count estimation for single-column indexes with NULL values #9474
- Specially handle
GROUP_CONCAT
when eliminating aggregate functions during the logical optimization phase to prevent incorrect executions #9967 - Properly push the filter down to child nodes of the join operator if the filter is a constant #9848
- Specially handle some functions such as
RAND()
when pruning columns during the logical optimization phase to prevent incompatibilities with MySQL #10064 - Support
FAST ANALYZE
, which speeds up statistics collection by sampling the region instead of scanning the entire region. This feature is controlled by the variabletidb_enable_fast_analyze
. #10258 - Support SQL Plan Management, which ensures execution stability by performing execution plan binding for SQL statements. This feature is currently in beta and only supports bound execution plans for SELECT statements. It is not recommended to use it in the production environment. #10284
- Support tracking and controlling memory usage in three operators -
TableReader
,IndexReader
andIndexLookupReader
#10003 - Support showing more information about coprocessor tasks in the slow log such as the number of tasks in coprocessor, the average/longest/90% of execution/waiting time and the addresses of the TiKVs which take the longest execution time or waiting time #10165
- Support the prepared DDL statements with no placeholders #10144
- Only allow the DDL owner to execute bootstrap when TiDB is started #10029
- Add the variable
tidb_skip_isolation_level_check
to prevent TiDB from reporting errors when setting the transaction isolation level to SERIALIZABLE #10065 - Merge the implicit commit time and the SQL execution time in the slow log #10294
- Support for SQL Roles (RBAC Privilege Management)
- Fix the
ConnectionEvent
error from thewhitelist
plugin that makes TiDB exit #9889 - Fix the issue of mistakenly adding read-only statements to the transaction history #9723
- Improve
kill
statements to stop SQL execution and release resources more quickly #9844 - Add a startup option
config-check
to check the validity of the configuration file #9855 - Fix the validity check of inserting NULL fields when the strict SQL mode is disabled #10161
- Add the
pre_split_regions
option forCREATE TABLE
statements; this option supports pre-splitting the Table Region when creating a table to avoid write hot spots caused by lots of writes after the table creation #10138 - Optimize the execution performance of some DDL statements #10170
- Add the warning that full-text indexes are not supported for
FULLTEXT KEY
#9821 - Fix the compatibility issue for the UTF8 and UTF8MB4 charsets in the old versions of TiDB #9820
- Fix the potential bug in
shard_row_id_bits
of a table #9868 - Fix the bug that the column charset is not changed after the table charset is changed #9790
- Fix a potential bug in
SHOW COLUMN
when usingBINARY
/BIT
as the column default value #9897 - Fix the compatibility issue in displaying
CHARSET
/COLLATION
descriptions in theSHOW FULL COLUMNS
statement #10007 - Fix the issue that the
SHOW COLLATIONS
statement only lists collations supported by TiDB #10186
- Fix compatibility of the
MAKETIME
function when unsigned type overflows #10089 - Fix the stack overflow caused by constant folding in some cases #10189
- Fix the privilege check issue for
Update
when an alias exists in some cases #10157, #10326 - Track and control memory usage in DistSQL #10197
- Support specifying collation as
utf8mb4_0900_ai_ci
#10201 - Fix the wrong result issue of the
MAX
function when the primary key is of the Unsigned type #10209 - Fix the issue that NULL values can be inserted into NOT NULL columns in the non-strict SQL mode #10254
- Fix the wrong result issue of the
COUNT
function when multiple columns exist inDISTINCT
#10270 - Fix the panic issue occurred when
LOAD DATA
parses irregular CSV files #10269 - Ignore the overflow error when the outer and inner join key types are inconsistent in
Index Lookup Join
#10244 - Fix the issue that a statement is wrongly judged as point-get in some cases #10299
- Fix the wrong result issue when the time type does not convert the time zone in some cases #10345
- Fix the issue that TiDB character set cases are inconsistent in some cases #10354
- Support controlling the number of rows returned by operator #9166
- Improve the slow query log:
- Add
SQL Digest
to distinguish similar SQL #10093 - Add version information of statistics used by slow query statements #10220
- Show memory consumption of a statement in slow query log #10246
- Adjust the output format of Coprocessor related information so it can be parsed by pt-query-digest #10300
- Fix the
#
character issue in slow query statements #10275 - Add some information columns to the memory table of slow query statements #10317
- Add the transaction commit time to slow query log #10310
- Fix the issue some time formats cannot be parsed by pt-query-digest #10323
- Add
- Fix the issue that the processing logic of
GROUP_CONCAT
function is incompatible with MySQL when there is a NULL-valued parameter #9930 - Fix the equality check issue of decimal values in the
Distinct
mode #9931 - Fix the collation compatibility issue of the date, datetime, and timestamp types for the
SHOW FULL COLUMNS
statement - Fix the issue that the row count estimation is inaccurate when the filtering condition contains correlated columns #9937
- Fix the compatibility issue between the
DATE_ADD
andDATE_SUB
functions - Support the
%H
format for theSTR_TO_DATE
function to improve compatibility #9964 - Fix the issue that the result is wrong when the
GROUP_CONCAT
function groups by a unique index #9969 - Return a warning when the Optimizer Hints contains an unmatched table name #9970
- Unify the log format to facilitate collecting logs using tools for analysis Unified Log Format
- Fix the issue that a lot of NULL values cause inaccurate statistics estimation #9979
- Fix the issue that an error is reported when the default value of the TIMESTAMP type is the boundary value #9987
- Validate the value of
time_zone
#10000 - Support the
2019.01.01
time format #10001 - Fix the issue that the row count estimation is displayed incorrectly in the result returned by the
EXPLAIN
statement in some cases #10044 - Fix the issue that
KILL TIDB [session id]
cannot instantly stop the execution of a statement in some cases #9976 - Fix the predicate pushdown issue of constant filtering conditions in some cases #10049
- Fix the issue that a read-only statement is not processed correctly in some cases #10048
- Fix the issue of longer startup time when upgrading the program caused by canceling DDL operations #9768
- Fix the issue that the
check-mb4-value-in-utf8
configuration item is in the wrong position in theconfig.example.toml
file #9852 - Improve the compatibility of the
str_to_date
built-in function with MySQL #9817 - Fix the compatibility issue of the
last_day
built-in function #9750 - Add the
tidb_table_id
column forinfoschema.tables
to facilitate gettingtable_id
by using SQL statements and add thetidb_indexes
system table to manage the relationship between Table and Index #9862 - Add a check about the null definition of Table Partition #9663
- Change the privileges required by
Truncate Table
fromDelete
toDrop
to make it consistent with MySQL #9876 - Support using subqueries in the
DO
statement #9877 - Fix the issue that the
default_week_format
variable does not take effect in theweek
function #9753 - Support the plugin framework #9880, #9888
- Support checking the enabling state of binlog by using the
log_bin
system variable #9634 - Support checking the Pump/Drainer status by using SQL statements #9896
- Fix the compatibility issue about checking mb4 character on utf8 when upgrading TiDB #9887
- Support calculating the Cartesian product by using
Sort Merge Join
#9032 - Support Skyline Pruning, with some rules to prevent the execution plan from relying too heavily on statistics #9337
- Support Window Functions
- Add a type of statistic that indicates the order correlation between columns and the handle column #9315
- Add built-in functions:
- Optimize the Chunk size based on the query context, to reduce the execution time of SQL statements and resources consumption of the cluster #6489
- Add the
/debug/zip
HTTP interface to get information of the current TiDB instance #9651 - Support the
show pump status
andshow drainer status
SQL statements to check the Pump or Drainer status 9456 - Support modifying the Pump or Drainer status by using SQL statements #9789
- Support adding HASH fingerprints to SQL text for easy tracking of slow SQL statements #9662
- Add the
log_bin
system variable ("0" by default) to control the enabling state of binlog; only support checking the state currently #9343 - Support managing the sending binlog strategy by using the configuration file #9864
- Support querying the slow log by using the
INFORMATION_SCHEMA.SLOW_QUERY
memory table #9290 - Change the MySQL version displayed in TiDB from 5.7.10 to 5.7.25 #9553
- Unify the log format for easy collection and analysis by tools
- Add the
high_error_rate_feedback_total
monitoring item to record the difference between the actual data volume and the estimated data volume based on statistics #9209 - Add the QPS monitoring item in the database dimension, which can be enabled by using a configuration item #9151
- Add the
ddl_error_count_limit
global variable ("512" by default) to limit the number of DDL task retries (If this number exceeds the limit, the DDL task is canceled) #9295 - Support ALTER ALGORITHM
INPLACE
/INSTANT
#8811 - Support the
SHOW CREATE VIEW
statement #9309 - Support the
SHOW CREATE USER
statement #9240
- Optimize planner to select the outer table based on cost when both tables are specified in Hint of
TIDB_INLJ
#9615 - Fix the issue that
IndexScan
cannot be selected correctly in some cases #9587 - Fix incompatibility with MySQL of check in the
agg
function in subqueries #9551 - Make
show stats_histograms
only output valid columns to avoid panics #9502
- Support the
log_bin
variable to enable/disable Binlog #9634 - Add a sanity check for transactions to avoid false transaction commit #9559
- Fix the issue that setting variables may lead to panic #9539
- Fix the issue that the
Create Table Like
statement causes panic in some cases #9652 - Enable the
AutoSync
feature of etcd clients to avoid connection issues between TiDB and etcd in some cases #9600
- Make
SHOW CREATE TABLE
do not print the column charset information when the charset information of a column is the same with that of a table, to improve the compatibility ofSHOW CREATE TABLE
with MySQL #9306 - Fix the panic or the wrong result of the
Sort
operator in some cases by extractingScalarFunc
fromSort
to aProjection
operator for computing to simplify the computing logic ofSort
#9319 - Remove the sorting field with constant values in the
Sort
operator #9335, #9440 - Fix the data overflow issue when inserting data into an unsigned integer column #9339
- Set
cast_as_binary
toNULL
when the length of the target binary exceedsmax_allowed_packet
#9349 - Optimize the constant folding process of
IF
andIFNULL
#9351 - Optimize the index selection of TiDB using skyline pruning to improve the stability of simple queries #9356
- Support computing the selectivity of the
DNF
expression #9405 - Fix the wrong SQL query result of
!=ANY()
and=ALL()
in some cases #9403 - Fix the panic or the wrong result when the Join Key types of two tables on which the
Merge Join
operation is performed are different #9438 - Fix the issue that the result of the
RAND()
function is not compatible with MySQL #9446 - Refactor the logic of
Semi Join
processingNULL
and the empty result set to get the correct result and improve the compatibility with MySQL #9449
- Add the
tidb_constraint_check_in_place
system variable to check the data uniqueness constraint when executing theINSERT
statement #9401 - Fix the issue that the value of the
tidb_force_priority
system variable is different from that set in the configuration file #9347 - Add the
current_db
field in general logs to print the name of the currently used database #9346 - Add an HTTP API of obtaining the table information with the table ID #9408
- Fix the issue that
LOAD DATA
loads incorrect data in some cases #9414 - Fix the issue that it takes a long time to build a connection between the MySQL client and TiDB in some cases #9451
- Fix some issues when canceling the
DROP COLUMN
operation #9352 - Fix some issues when canceling the
DROP
orADD
partitioned table operation #9376 - Fix the issue that
ADMIN CHECK TABLE
mistakenly reports the data index inconsistency in some cases #9399 - Fix the time zone issue of the
TIMESTAMP
default value #9108
- Fix the issue that the
VALUES
function does not handle the FLOAT type correctly #9223 - Fix the wrong result issue when casting Float to String in some cases #9227
- Fix the wrong result issue of the
FORMAT
function in some cases #9235 - Fix the panic issue when handling the Join query in some cases #9264
- Fix the issue that the
VALUES
function does not handle the ENUM type correctly #9280 - Fix the wrong result issue of
DATE_ADD
/DATE_SUB
in some cases #9284
- Optimize the "reload privilege success" log and change it to the DEBUG level #9274
- Change
tidb_ddl_reorg_worker_cnt
andtidb_ddl_reorg_batch_size
to global variables #9134 - Fix the bug caused by adding an index to a generated column in some abnormal conditions #9289
- Fix the panic issue of Prepared Plan Cache in some cases #8826
- Fix the issue that Range computing is wrong when the index is a prefix index #8851
- Make
CAST(str AS TIME(N))
return null if the string is in the illegalTIME
format whenSQL_MODE
is not strict #8966 - Fix the panic issue of Generated Column during the process of
UPDATE
in some cases #8980 - Fix the upper bound overflow issue of the statistics histogram in some cases #8989
- Support Range for
_tidb_rowid
construction queries, to avoid full table scan and reduce cluster stress #9059 - Return an error when the
CAST(AS TIME)
precision is too big #9058 - Allow using
Sort Merge Join
in the Cartesian product #9037 - Fix the issue that the statistics worker cannot resume after the panic in some cases #9085
- Fix the issue that
Sort Merge Join
returns the wrong result in some cases #9046 - Support returning the JSON type in the
CASE
clause #8355
- Return a warning instead of an error when the non-TiDB hint exists in the comment #8766
- Verify the validity of the configured TIMEZONE value #8879
- Optimize the
QueryDurationHistogram
metrics item to display more statement types #8875 - Fix the lower bound overflow issue of bigint in some cases #8544
- Support the
ALLOW_INVALID_DATES
SQL mode #9110
- Fix a
RENAME TABLE
compatibility issue to keep the behavior consistent with that of MySQL #8808 - Support making concurrent changes of
ADD INDEX
take effect immediately #8786 - Fix the
UPDATE
panic issue during the process ofADD COLUMN
in some cases #8906 - Fix the issue of concurrently creating Table Partition in some cases #8902
- Support converting the
utf8
character set toutf8mb4
#8951 #9152 - Fix the issue of Shard Bits overflow #8976
- Support outputting the column character sets in
SHOW CREATE TABLE
#9053 - Fix the issue of the maximum length limit of the varchar type column in
utf8mb4
#8818 - Support
ALTER TABLE TRUNCATE TABLE PARTITION
#9093 - Resolve the charset when the charset is not provided #9147
- Support View
- Support Window Function
- Support Range Partition
- Support Hash Partition
- Re-support the optimization rule of
AggregationElimination
#7676 - Optimize the
NOT EXISTS
subquery and convert it to Anti Semi Join #7842 - Add the
tidb_enable_cascades_planner
variable to support the new Cascades optimizer. Currently, the Cascades optimizer is not yet fully implemented and is turned off by default #7879 - Support using Index Join in transactions #7877
- Optimize the constant propagation on the Outer Join, so that the filtering conditions related to the Outer table in the Join result can be pushed down through the Outer Join to the Outer table, reducing the useless calculation of the Outer Join and improving the execution performance #7794
- Adjust the optimization rule of Projection Elimination to the position after the Aggregation Elimination, to avoid redundant
Project
operators #7909 - Optimize the
IFNULL
function and eliminate this function when the input parameter has a non-NULL attribute #7924 - Support building range for
_tidb_rowid
, to avoid full table scan and reduce cluster stress #8047 - Optimize the
IN
subquery to do the Inner Join after the aggregation, and add thetidb_opt_insubq_to_join_and_agg
variable to control whether to enable this optimization rule and open it by default #7531 - Support using subqueries in the
DO
statement #8343 - Add the optimization rule of Outer Join elimination to reduce unnecessary table scan and Join operations and improve execution performance #8021
- Modify the Hint behavior of the
TIDB_INLJ
optimizer, and the optimizer will use the table specified in Hint as the Inner table of Index Join #8243 - Use
PointGet
in a wide range so that it can be used when the execution plan cache of thePrepare
statement takes effect #8108 - Introduce the greedy
Join Reorder
algorithm to optimize the join order selection when joining multiple tables #8394 - Support View #8757
- Support Window Function #8630
- Return warning to the client when
TIDB_INLJ
is not in effect, to enhance usability #9037 - Support deducing the statistics for filtered data based on filtering conditions and table statistics #7921
- Improve the Partition Pruning optimization rule of Range Partition #8885
- Optimize the
Merge Join
operator to support the emptyON
condition #9037 - Optimize the log and print the user variables used when executing the
EXECUTE
statement #7684 - Optimize the log to print slow query information for the
COMMIT
statement #7951 - Support the
EXPLAIN ANALYZE
feature to make the SQL tuning process easier #7827 - Optimize the write performance of wide tables with many columns #7935
- Support
admin show next_row_id
#8242 - Add the
tidb_init_chunk_size
variable to control the size of the initial Chunk used by the execution engine #8480 - Improve
shard_row_id_bits
and cross-check the auto-increment ID #8936
- Prohibit adding the
Prepare
statement containing subqueries to the query plan cache to guarantee the query plan is correct when different user variables are input #8064 - Optimize the query plan cache to guarantee the plan can be cached when the statement contains non-deterministic functions #8105
- Optimize the query plan cache to guarantee the query plan of
DELETE
/UPDATE
/INSERT
can be cached #8107 - Optimize the query plan cache to remove the corresponding plan when executing the
DEALLOCATE
statement #8332 - Optimize the query plan cache to avoid the TiDB OOM issue caused by caching too many plans by limiting the memory usage #8339
- Optimize the
Prepare
statement to support using the?
placeholder in theORDER BY
/GROUP BY
/LIMIT
clause #8206
- Add the privilege check for the
ANALYZE
statement #8486 - Add the privilege check for the
USE
statement #8414 - Add the privilege check for the
SET GLOBAL
statement #8837 - Add the privilege check for the
SHOW PROCESSLIST
statement #7858
- Support the
Trace
feature #9029 - Support the plugin framework #8788
- Support using
unix_socket
and TCP simultaneously to connect to the database #8836 - Support the
interactive_timeout
system variable #8573 - Support the
wait_timeout
system variable #8346 - Support splitting a transaction into multiple transactions based on the number of statements using the
tidb_batch_commit
variable #8293 - Support using the
ADMIN SHOW SLOW
statement to check slow logs #7785
- Support the
ALLOW_INVALID_DATES
SQL mode #9027 - Improve
LoadData
fault-tolerance for the CSV file #9005 - Support the MySQL 320 handshake protocol #8812
- Support using the unsigned bigint column as the auto-increment column #8181
- Support the
SHOW CREATE DATABASE IF NOT EXISTS
syntax #8926 - Abandon the predicate pushdown operation when the filtering condition contains a user variable to improve the compatibility with MySQL's behavior of using user variables to mock the Window Function behavior #8412
- Support fast recovery of mistakenly deleted tables #7937
- Support adjusting the number of concurrencies of
ADD INDEX
dynamically #8295 - Support changing the character set of tables or columns to
utf8
/utf8mb4
#8037 - Change the default character set from
utf8
toutf8mb4
#7965 - Support Range Partition #8011
- Make TiDB compatible with TiDB-Binlog of the Kafka version #8747
- Improve the exit mechanism of TiDB in a rolling update #8707
- Fix the panic issue caused by adding the index for the generated column in some cases #8676
- Fix the issue that the optimizer cannot find the optimal query plan when
TIDB_SMJ Hint
exists in the SQL statement in some cases #8729 - Fix the issue that
AntiSemiJoin
returns an incorrect result in some cases #8730 - Improve the valid character check of the
utf8
character set #8754 - Fix the issue that the field of the time type might return an incorrect result when the write operation is performed before the read operation in a transaction #8746
- Fix the round error of the negative date #8574
- Fix the issue that the
uncompress
function does not check the data length #8606 - Reset bind arguments of the
prepare
statement after theexecute
command is executed #8652 - Support automatically collecting the statistics information of a partition table #8649
- Fix the wrongly configured integer type when pushing down the
abs
function #8628 - Fix the data race on the JSON column #8660
- Fix the issue that the transaction obtained TSO is incorrect when PD breaks down #8567
- Fix the bootstrap failure caused by the statement that does not conform to ANSI standards #8576
- Fix the issue that incorrect parameters are used in transaction retries #8638
- Change the default character set and collation of tables into
utf8mb4
#8590 - Add the
ddl_reorg_batch_size
variable to control the speed of adding indexes #8614 - Make the character set and collation options content in DDL case-insensitive #8611
- Fix the issue of adding indexes for generated columns #8655
- TiDB 2.1 does not support downgrading to v2.0.x or earlier due to the adoption of the new storage engine
- Parallel DDL is enabled in TiDB 2.1, so the clusters with TiDB version earlier than 2.0.1 cannot upgrade to 2.1 using rolling update. You can choose either of the following two options:
- Stop the cluster and upgrade to 2.1 directly
- Roll update to 2.0.1 or later 2.0.x versions, and then roll update to the 2.1 version
raft learner
is enabled in TiDB 2.1 by default. If you upgrade the TiDB platform from 1.x to 2.1, stop the cluster before the upgrade. You can also roll update TiKV to 2.1 and then roll update PD to 2.1.- If you upgrade from TiDB 2.0.6 or earlier to TiDB 2.1, make sure if there is any ongoing DDL operation, especially the time consuming
Add Index
operation, because the DDL operations slow down the upgrading process.
- Optimize the selection range of
Index Join
to improve the execution performance - Optimize the selection of outer table for
Index Join
and use the table with smaller estimated value of Row Count as the outer table - Optimize Join Hint
TIDB_SMJ
so that Merge Join can be used even without proper index available - Optimize Join Hint
TIDB_INLJ
to specify the Inner table to Join - Optimize correlated subquery, push down Filter, and extend the index selection range, to improve the efficiency of some queries by orders of magnitude
- Support using Index Hint and Join Hint in the
UPDATE
andDELETE
statement - Support pushing down more functions:
ABS
/CEIL
/FLOOR
/IS TRUE
/IS FALSE
- Optimize the constant folding algorithm for the
IF
andIFNULL
built-in functions - Optimize the output of the
EXPLAIN
statement and use hierarchy structure to show the relationship between operators
- Refactor all the aggregation functions and improve execution efficiency of the
Stream
andHash
aggregation operators - Implement the parallel
Hash Aggregate
operators and improve the computing performance by 350% in some scenarios - Implement the parallel
Project
operators and improve the performance by 74% in some scenarios - Read the data of the Inner table and Outer table of
Hash Join
concurrently to improve the execution performance - Optimize the execution speed of the
REPLACE INTO
statement and increase the performance nearly by 10 times - Optimize the memory usage of the time data type and decrease the memory usage of the time data type by fifty percent
- Optimize the point select performance and improve the point select efficiency result of Sysbench by 60%
- Improve the performance of TiDB on inserting or updating wide tables by 20 times
- Support configuring the memory upper limit of a single statement in the configuration file
- Optimize the execution of Hash Join, if the Join type is Inner Join or Semi Join and the inner table is empty, return the result without reading data from the outer table
- Support using the
EXPLAIN ANALYZE
statement to check the runtime statistics including the execution time and the number of returned rows of each operator
- Support enabling auto ANALYZE statistics only during certain period of the day
- Support updating the table statistics automatically according to the feedback of the queries
- Support configuring the number of buckets in the histogram using the
ANALYZE TABLE WITH BUCKETS
statement - Optimize the Row Count estimation algorithm using histogram for mixed queries of equality query and range queries
- Support following built-in function:
json_contains
json_contains_path
encode/decode
- Support queuing the locally conflicted transactions within tidb-server instance to optimize the performance of conflicted transactions
- Support Server Side Cursor
- Add the HTTP API
- Scatter the distribution of table Regions in the TiKV cluster
- Control whether to open the
general log
- Support modifying the log level online
- Check the TiDB cluster information
- Add the
auto_analyze_ratio
system variables to contorl the ratio of Analyze - Add the
tidb_retry_limit
system variable to control the automatic retry times of transactions - Add the
tidb_disable_txn_auto_retry
system variable to control whether the transaction retries automatically - Support using
admin show slow
statement to obtain the slow queries - Add the
tidb_slow_log_threshold
environment variable to set the threshold of slow log automatically - Add the
tidb_query_log_max_len
environment variable to set the length of the SQL statement to be truncated in the log dynamically
- Support the parallel execution of the add index statement and other statements to avoid the time consuming add index operation blocking other operations
- Optimize the execution speed of
ADD INDEX
and improve it greatly in some scenarios - Support the
select tidb_is_ddl_owner()
statement to facilitate deciding whether TiDB isDDL Owner
- Support the
ALTER TABLE FORCE
syntax - Support the
ALTER TABLE RENAME KEY TO
syntax - Add the table name and database name in the output information of
admin show ddl jobs
- Support using the
ddl/owner/resign
HTTP interface to release the DDL owner and start electing a new DDL owner
- Support more MySQL syntaxes
- Make the
BIT
aggregate function support theALL
parameter - Support the
SHOW PRIVILEGES
statement - Support the
CHARACTER SET
syntax in theLOAD DATA
statement - Support the
IDENTIFIED WITH
syntax in theCREATE USER
statement - Support the
LOAD DATA IGNORE LINES
statement - The
Show ProcessList
statement returns more accurate information
- Fix the issue that
IndexReader
reads the wrong handle in some cases #8132 - Fix the issue occurred while the
IndexScan Prepared
statement usesPlan Cache
#8055 - Fix the issue that the result of the
Union
statement is unstable #8165
- Improve the performance of TiDB on inserting or updating wide tables #8024
- Support the unsigned
int
flag in theTruncate
built-in function #8068 - Fix the error occurred while converting JSON data to the decimal type #8109
- Fix the error occurred when you
Update
the float type #8170
- Fix the incorrect statistics issue during point queries in some cases #8035
- Fix the selectivity estimation of statistics for primary key in some cases #8149
- Fix the issue that the statistics of deleted tables are not cleared up for a long period of time #8182
- Improve the readability of logs and make logs better
- Fix the error occurred when obtaining the table data of
infoschema.profiling
#8096 - Replace the unix socket with the pumps client to write binlogs #8098
- Add the threshold value for the
tidb_slow_log_threshold
environment variable, which dynamically sets the slow log #8094 - Add the original length of a SQL statement truncated while the
tidb_query_log_max_len
environment variable dynamically sets logs 8200 - Add the
tidb_opt_write_row_id
environment variable to control whether to allow writing_tidb_rowid
#8218 - Add an upper bound to the
Scan
command of ticlient, to avoid overbound scan #8081, #8247
- Fix the issue that executing DDL statements in transactions encounters an error in some cases #8056
- Fix the issue that executing
truncate table
in partition tables does not take effect #8103 - Fix the issue that the DDL operation does not roll back correctly after being cancelled in some cases #8057
- Add the
admin show next_row_id
command to return the next available row ID #8268
- 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
- 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
- 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
- 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 theLOAD DATA
statement #8005 - Complete the "coprocessor error" log information #8006
- Set the
Command
field of theSHOW PROCESSLIST
result toSleep
when the query is empty #7839
- Fix the constant folding issue of the
SYSDATE
function #7895 - Fix the issue that
SUBSTRING_INDEX
panics in some cases #7897
- 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
- Put forward a proposal of the next generation Planner #7543
- Improve the optimization rules of constant propagation #7276
- Enhance the computing logic of
Range
to enable it to handle multipleIN
orEQUAL
conditions simultaneously #7577 - Fix the issue that the estimation result of
TableScan
is incorrect whenRange
is empty #7583 - Support the
PointGet
operator for theUPDATE
statement #7586 - Fix the panic issue during the process of executing the
FirstRow
aggregate function in some conditions #7624
- Fix the potential
DataRace
issue when theHashJoin
operator encounters an error #7554 - Make the
HashJoin
operator read the inner table and build the hash table simultaneously #7544 - Optimize the performance of Hash aggregate operators #7541
- Optimize the performance of Join operators #7493, #7433
- Fix the issue that the result of
UPDATE JOIN
is incorrect when the Join order is changed #7571 - Improve the performance of Chunk's iterator #7585
- Fix the issue that the auto Analyze work repeatedly analyzes the statistics #7550
- Fix the statistics update error that occurs when there is no statistics change #7530
- Use the RC isolation level and low priority when building
Analyze
requests #7496 - Support enabling statistics auto-analyze on certain period of a day #7570
- Fix the panic issue when logging the statistics information #7588
- Support configuring the number of buckets in the histogram using the
ANALYZE TABLE WITH BUCKETS
statement #7619 - Fix the panic issue when updating an empty histogram #7640
- Update
information_schema.tables.data_length
using the statistics information #7657
- Add Trace related dependencies #7532
- Enable the
mutex profile
feature of Golang #7512 - The
Admin
statement requires theSuper_priv
privilege #7486 - Forbid users to
Drop
crucial system tables #7471 - Switch from
juju/errors
topkg/errors
#7151 - Complete the functional prototype of SQL Tracing #7016
- Remove the goroutine pool #7564
- Support viewing the goroutine information using the
USER1
signal #7587 - Set the internal SQL to high priority while TiDB is started #7616
- Use different labels to filter internal SQL and user SQL in monitoring metrics #7631
- Store the top 30 slow queries in the last week to the TiDB server #7646
- Put forward a proposal of setting the global system time zone for the TiDB cluster #7656
- Enrich the error message of "GC life time is shorter than transaction duration" #7658
- Set the global system time zone when starting the TiDB cluster #7638
- Add the unsigned flag for the
Year
type #7542 - Fix the issue of configuring the result length of the
Year
type in thePrepare
/Execute
mode #7525 - Fix the issue of inserting zero timestamp in the
Prepare
/Execute
mode #7506 - Fix the error handling issue of the integer division #7492
- Fix the compatibility issue when processing
ComStmtSendLongData
#7485 - Fix the error handling issue during the process of converting string to integer #7483
- Optimize the accuracy of values in the
information_schema.columns_in_table
table #7463 - Fix the compatibility issue when writing or updating the string type of data using the MariaDB client #7573
- Fix the compatibility issue of aliases of the returned value #7600
- Fix the issue that the
NUMERIC_SCALE
value of the float type is incorrect in theinformation_schema.COLUMNS
table #7602 - Fix the issue that Parser reports an error when the single line comment is empty #7612
- Check the value of
max_allowed_packet
in theinsert
function #7528 - Support the built-in function
json_contains
#7443 - Support the built-in function
json_contains_path
#7596 - Support the built-in function
encode/decode
#7622 - Fix the issue that some time related functions are not compatible with the MySQL behaviors in some cases #7636
- Fix the compatibility issue of parsing the time type of data in string #7654
- Fix the issue that the time zone is not considered when computing the default value of the
DateTime
data #7655
- Set correct
last_insert_id
in theInsertOnDuplicateUpdate
statement #7534 - Reduce the cases of updating the
auto_increment_id
counter #7515 - Optimize the error message of
Duplicate Key
#7495 - Fix the
insert...select...on duplicate key update
issue #7406 - Support the
LOAD DATA IGNORE LINES
statement #7576
- Add the DDL job type and the current schema version information in the monitor #7472
- Complete the design of the
Admin Restore Table
feature #7383 - Fix the issue that the default value of the
Bit
type exceeds 128 #7249 - Fix the issue that the default value of the
Bit
type cannot beNULL
#7604 - Reduce the interval of checking
CREATE TABLE/DATABASE
in the DDL queue #7608 - Use the
ddl/owner/resign
HTTP interface ro release the DDL owner and start electing a new owner #7649
- Support the issue that the
Seek
operation only obtainsKey
#7419
Table Partition (Experimental)
- Fix the issue that the
Bigint
type cannot be used as the partition key #7520 - Support the rollback operation when an issue occurs during adding an index in the partitioned table #7437
- Support showing memory usage of the executing statements in the
SHOW PROCESSLIST
statement - Support setting the table comment using the
Alter
statement
- Clean up the written data while rolling back the
Add Index
operation, to reduce consumed space - Optimize the insert on duplicate key update statement to improve the performance by 10 times
- Fix the issue about applying the Top-N pushdown rule
- Fix the issue that
Alter Table Modify Column
reports an error in extreme conditions - Fix the issue about the type of the results returned by the
UNIX_TIMESTAMP
function - Fix the issue that the NULL value is inserted while adding NOT NULL columns
- Fix the estimation of the number of rows for the columns that contain NULL values
- Fix the zero value of the Binary type
- Fix the BatchGet issue within a transaction
- Support
SHOW GRANTS FOR CURRENT_USER();
- Support the
SET TRANSACTION
syntax - Support displaying floating point numbers using scientific notation
- Improve the execution performance of
DecodeBytes
- Optimize
LIMIT 0
toTableDual
, to avoid building useless execution plans
- Fix the issue that the
Expression
inUnionScan
is not cloned - Fix the potential goroutine leak issue in
copIterator
- Fix the issue that admin check table misjudges the unique index including null
- Fix the type inference issue during binary literal computing
- Fix the issue in parsing the
CREATE VIEW
statement - Fix the panic issue when one statement contains both
ORDER BY
andLIMIT 0
- Support closing the
Join Reorder
optimization in the optimizer usingSTRAIGHT_JOIN
- Output more detailed status information of DDL jobs in
ADMIN SHOW DDL JOBS
- Support querying the original statements of currently running DDL jobs using
ADMIN SHOW DDL JOB QUERIES
- Support recovering the index data using
ADMIN RECOVER INDEX
for disaster recovery - Attach a lower priority to the
ADD INDEX
operation to reduce the impact on online business - Support aggregation functions with JSON type parameters, such as
SUM/AVG
- Support modifying the
lower_case_table_names
system variable in the configuration file, to support the OGG data synchronization tool - Support using implicit
RowID
in CRUD operations
- Improve compatibility with the Navicat management tool
- Use the Stream Aggregation operator when the
GROUP BY
clause is empty, to increase the speed - Optimize the execution speed of
ADD INDEX
to greatly increase the speed in some scenarios - Optimize checks on length and precision of the floating point type, to improve compatibility with MySQL
- Improve the parsing error log of time type and add more error information
- Improve memory control and add statistics about
IndexLookupExecutor
memory
- Fix the wrong result issue of
MAX/MIN
in some scenarios - Fix the issue that the result of
Sort Merge Join
does not show in order ofJoin Key
in some scenarios - Fix the error of comparison between uint and int in boundary conditions
Only TiKV has this release
- Support limiting the memory usage by a single SQL statement, to reduce the risk of OOM
- Support pushing the Stream Aggregate operator down to TiKV
- Support validating the configuration file
- Support obtaining the information of TiDB configuration through HTTP API
- Improve the compatibility with Navicat
- Improve the optimizer and extract common expressions with multiple OR conditions, to choose better query plan
- Improve the optimizer and convert subqueries to Join operators in more scenarios, to choose better query plan
- Compatible with more MySQL syntax in Parser
- Resolve Lock in the Batch mode to increase the garbage collection speed
- Optimize the
Add Index
operation and give lower priority to all write and read operations, to reduce the impact on online business
- Fix the length of Boolean field to improve compatibility
- Add more monitoring metrics and refine the log
- Add the
tidb_config
session variable to output the current TiDB configuration - Support displaying the table creating time in
information_schema
- Compatible with more MySQL syntax
- Optimize queries containing the
MaxOneRow
operator - Configure the size of intermediate result sets generated by Join, to further reduce the memory used by Join
- Optimize the query performance of the SQL engine to improve the test result of the Sysbench Select/OLTP by 10%
- Improve the computing speed of subqueries in the optimizer using the new execution engine; compared with TiDB 1.0, TiDB 1.1 Beta has great improvement in tests like TPC-H and TPC-DS
- Fix the panic issue in the
Union
andIndex Join
operators - Fix the wrong result issue of the
Sort Merge Join
operator in some scenarios - Fix the issue that the
Show Index
statement shows indexes that are in the process of adding - Fix the failure of the
Drop Stats
statement
- Add limitation (Configurable, the default value is 5000) to the DML statements number within a transaction
- Improve the stability of the GC process by ignoring the regions with GC errors
- Run GC concurrently to accelerate the GC process
- Provide syntax support for the
CREATE INDEX
statement - Optimize the performance of the
InsertIntoIgnore
statement
- Fix issues in the
Outer Join
result in some scenarios - Fix the issue in the
ShardRowID
option - Fix an issue in the
Table/Column
aliases returned by the Prepare statement - Fix an issue in updating statistics delta
- Fix a panic error in the
Drop Column
statement - Fix an DML issue when running the
Add Column After
statement
- Optimize the
FIELD_LIST
command - Fix data race of the information schema
- Avoid adding read-only statements to history
- Add the session variable to control the log query
- Add schema info API for the http status server
- Update the behavior when
RunWorker
is false in DDL - Improve the stability of test results in statistics
- Support
PACK_KEYS
syntax for theCREATE TABLE
statement - Add
row_id
column for the null pushdown schema to optimize performance
- Fix the resource leak issue in statistics
- Fix the goroutine leak issue
- Fix an issue about
IndexJoin
- Support the PROXY protocol
- Support more syntax
- Reduce memory usage of statistics info using more compact structure
- Speed up loading statistics info when starting tidb-server
- Provide more accurate query cost evaluation
- Use
Count-Min Sketch
to estimate the cost of queries using unique index more accurately - Support more complex conditions to make full use of index
- Refactor all executor operators using Chunk architecture, improve the execution performance of analytical statements and reduce memory usage
- Optimize performance of the
INSERT IGNORE
statement - Push down more types and functions to TiKV
- Support more
SQL_MODE
- Optimize the
Load Data
performance to increase the speed by 10 times - Optimize the
Use Database
performance - Support statistics on the memory usage of physical operators