Release of Vitess v20.0.0

Summary

Major Changes
Minor Changes

Major Changes

Deletion

`--vreplication_tablet_type` flag

The previously deprecated flag --vreplication_tablet_type has been deleted.

Pool Capacity Flags

The previously deprecated flags --queryserver-config-query-pool-waiter-cap, --queryserver-config-stream-pool-waiter-cap and --queryserver-config-txpool-waiter-cap have been deleted.

`vitess/base` and `vitess/k8s` Docker images

Since we have deleted MySQL from our vitess/lite image, we are removing the vitess/base and vitess/k8s images.

These images are no longer useful since we can use vitess/lite as the base of many other Docker images (vitess/vtgate, vitess/vtgate, ...).

`gh-ost` binary and endtoend tests

Vitess 20.0 drops support for gh-ost DDL strategy.

vttablet binary no longer embeds a gh-ost binary. Users of gh-ost DDL strategy will need to supply a gh-ost binary on the vttablet host or pod. Vitess will look for the gh-ost binary in the system PATH; otherwise the user should supply vttablet --gh-ost-path.

Vitess' endtoend tests no longer use nor test gh-ost migrations.

Legacy `EmergencyReparentShard` stats

The following EmergencyReparentShard stats were deprecated in Vitess 18.0 and are removed in Vitess 20.0:

ers_counter
ers_success_counter
ers_failure_counter

These counters are replaced by the following stats (introduced in Vitess 18.0):

emergency_reparent_counts - Number of times EmergencyReparentShard has been run. It is further subdivided by the keyspace, shard and the result of the operation.
planned_reparent_counts - Number of times PlannedReparentShard has been run. It is further subdivided by the keyspace, shard and the result of the operation.

Also, the reparent_shard_operation_timings stat was added to provide per-operation timings of reparent operations.

Breaking Changes

Metric Name Changes in VTOrc

The following metric names have been changed in VTOrc. The old metrics are still available in /debug/vars for this release, but will be removed in later releases. The new metric names and the deprecated metric names resolve to the same metric name on prometheus, so there is no change there.

Old Metric Name	New Metric Name	Name in Prometheus
`analysis.change.write`	`AnalysisChangeWrite`	`vtorc_analysis_change_write`
`audit.write`	`AuditWrite`	`vtorc_audit_write`
`discoveries.attempt`	`DiscoveriesAttempt`	`vtorc_discoveries_attempt`
`discoveries.fail`	`DiscoveriesFail`	`vtorc_discoveries_fail`
`discoveries.instance_poll_seconds_exceeded`	`DiscoveriesInstancePollSecondsExceeded`	`vtorc_discoveries_instance_poll_seconds_exceeded`
`discoveries.queue_length`	`DiscoveriesQueueLength`	`vtorc_discoveries_queue_length`
`discoveries.recent_count`	`DiscoveriesRecentCount`	`vtorc_discoveries_recent_count`
`instance.read`	`InstanceRead`	`vtorc_instance_read`
`instance.read_topology`	`InstanceReadTopology`	`vtorc_instance_read_topology`
`emergency_reparent_counts`	`EmergencyReparentCounts`	`vtorc_emergency_reparent_counts`
`planned_reparent_counts`	`PlannedReparentCounts`	`vtorc_planned_reparent_counts`
`reparent_shard_operation_timings`	`ReparentShardOperationTimings`	`vtorc_reparent_shard_operation_timings_bucket`

ENUM and SET column handling in VTGate VStream API

The VTGate VStream API now returns ENUM and SET column type values in VEvent messages (in the embedded RowChange messages) as their string values instead of the integer based ones — in both the copy/snapshot phase and the streaming phase. This change was done to make the VStream API more user-friendly, intuitive, and to align the behavior across both phases. Before this change the values for ENUM and SET columns were string values in the copy phase but integer values (which only have an internal meaning to MySQL) in the streaming phase. This inconsistency led to various challenges and issues for each VStream client/consumer (e.g. the Debezium Vitess connector failed to properly perform a snapshot for tables containing these column types). Now the behavior is intuitive — clients need the string values as the eventual sink is often not MySQL so each consumer needed to perform the mappings themselves — and consistent. While this is a (potentially) breaking change, a new boolean field has been added to the FieldEvent message called EnumSetStringValues. When that field is false (in Vitess v19 and older) then the consumer will need to perform the mappings during streaming phase, but not during copy phase. When this field is true, then no mapping is required. This will help to ensure a smooth transition for all consumers over time. To demonstrate, let's look at the textual output (printing the received VEvents as strings) when streaming a single enum_set_test table from the unsharded commerce keyspace so that we can see what the VStream looks like before and after when we start a new VStream in copy/snapshot mode and then transition to streaming mode for the following table:

CREATE TABLE `enum_set_test` (
  `id` int NOT NULL AUTO_INCREMENT,
  `name` varchar(120) DEFAULT NULL,
  `shirt_size` enum('small','medium','large','xlarge','xxlarge') DEFAULT NULL,
  `hobbies` set('knitting','cooking','pickleball','biking','hiking','motorcycle','video games','reading') DEFAULT NULL,
  PRIMARY KEY (`id`)
)

And with the table having this data when we start our VStream and begin the copy/snapshot phase:

mysql> select * from enum_set_test;
+----+-----------+------------+-------------------------+
| id | name      | shirt_size | hobbies                 |
+----+-----------+------------+-------------------------+
|  1 | Billy Bob | xlarge     | cooking,reading         |
|  2 | Sally Mae | medium     | knitting,cooking,hiking |
+----+-----------+------------+-------------------------+
2 rows in set (0.00 sec)

And finally we will perform the following inserts and updates to the table during the streaming phase:

insert into enum_set_test values (3, "Matt Lord", 'medium', 'pickleball,biking,hiking,motorcycle,video games,reading');
insert into enum_set_test values (4, "Jerry Badyellow", 'large', '');
update enum_set_test set shirt_size = 'small', hobbies = 'knitting,cooking,hiking,reading' where id = 2;

Vitess v19 and older:

[type:BEGIN keyspace:"commerce" shard:"0" type:FIELD field_event:{table_name:"commerce.enum_set_test" fields:{name:"id" type:INT32 table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"id" column_length:11 charset:63 flags:49667 column_type:"int"} fields:{name:"name" type:VARCHAR table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"name" column_length:480 charset:255 column_type:"varchar(120)"} fields:{name:"shirt_size" type:ENUM table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"shirt_size" column_length:28 charset:255 flags:256 column_type:"enum('small','medium','large','xlarge','xxlarge')"} fields:{name:"hobbies" type:SET table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"hobbies" column_length:288 charset:255 flags:2048 column_type:"set('knitting','cooking','pickleball','biking','hiking','motorcycle','video games','reading')"} keyspace:"commerce" shard:"0"} keyspace:"commerce" shard:"0"]
[type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/ce357206-0d49-11ef-8fd1-a74564279579:1-35"}} keyspace:"commerce" shard:"0"]
[type:ROW row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:9 lengths:6 lengths:15 values:"1Billy Bobxlargecooking,reading"}} keyspace:"commerce" shard:"0"} keyspace:"commerce" shard:"0" type:ROW row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:9 lengths:6 lengths:23 values:"2Sally Maemediumknitting,cooking,hiking"}} keyspace:"commerce" shard:"0"} keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/ce357206-0d49-11ef-8fd1-a74564279579:1-35" table_p_ks:{table_name:"enum_set_test" lastpk:{fields:{name:"id" type:INT32 charset:63 flags:49667} rows:{lengths:1 values:"2"}}}}} keyspace:"commerce" shard:"0" type:COMMIT keyspace:"commerce" shard:"0"]
[type:BEGIN keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/ce357206-0d49-11ef-8fd1-a74564279579:1-35"}} keyspace:"commerce" shard:"0" type:COMMIT keyspace:"commerce" shard:"0"]
[type:COPY_COMPLETED keyspace:"commerce" shard:"0" type:COPY_COMPLETED]
[type:BEGIN timestamp:1715179728 current_time:1715179728532658000 keyspace:"commerce" shard:"0" type:FIELD timestamp:1715179728 field_event:{table_name:"commerce.enum_set_test" fields:{name:"id" type:INT32 table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"id" column_length:11 charset:63 flags:49667 column_type:"int"} fields:{name:"name" type:VARCHAR table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"name" column_length:480 charset:255 column_type:"varchar(120)"} fields:{name:"shirt_size" type:ENUM table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"shirt_size" column_length:28 charset:255 flags:256 column_type:"enum('small','medium','large','xlarge','xxlarge')"} fields:{name:"hobbies" type:SET table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"hobbies" column_length:288 charset:255 flags:2048 column_type:"set('knitting','cooking','pickleball','biking','hiking','motorcycle','video games','reading')"} keyspace:"commerce" shard:"0"} current_time:1715179728535652000 keyspace:"commerce" shard:"0" type:ROW timestamp:1715179728 row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:9 lengths:1 lengths:3 values:"3Matt Lord2252"}} keyspace:"commerce" shard:"0" flags:1} current_time:1715179728535739000 keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/ce357206-0d49-11ef-8fd1-a74564279579:1-36"}} keyspace:"commerce" shard:"0" type:COMMIT timestamp:1715179728 current_time:1715179728535754000 keyspace:"commerce" shard:"0"]
[type:BEGIN timestamp:1715179735 current_time:1715179735538607000 keyspace:"commerce" shard:"0" type:ROW timestamp:1715179735 row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:15 lengths:1 lengths:1 values:"4Jerry Badyellow30"}} keyspace:"commerce" shard:"0" flags:1} current_time:1715179735538659000 keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/ce357206-0d49-11ef-8fd1-a74564279579:1-37"}} keyspace:"commerce" shard:"0" type:COMMIT timestamp:1715179735 current_time:1715179735538672000 keyspace:"commerce" shard:"0"]
[type:BEGIN timestamp:1715179741 current_time:1715179741728690000 keyspace:"commerce" shard:"0" type:ROW timestamp:1715179741 row_event:{table_name:"commerce.enum_set_test" row_changes:{before:{lengths:1 lengths:9 lengths:1 lengths:2 values:"2Sally Mae219"} after:{lengths:1 lengths:9 lengths:1 lengths:3 values:"2Sally Mae1147"}} keyspace:"commerce" shard:"0" flags:1} current_time:1715179741728730000 keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/ce357206-0d49-11ef-8fd1-a74564279579:1-38"}} keyspace:"commerce" shard:"0" type:COMMIT timestamp:1715179741 current_time:1715179741728744000 keyspace:"commerce" shard:"0"]

Vitess v20 and newer:

[type:BEGIN keyspace:"commerce" shard:"0" type:FIELD field_event:{table_name:"commerce.enum_set_test" fields:{name:"id" type:INT32 table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"id" column_length:11 charset:63 flags:49667 column_type:"int"} fields:{name:"name" type:VARCHAR table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"name" column_length:480 charset:255 column_type:"varchar(120)"} fields:{name:"shirt_size" type:ENUM table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"shirt_size" column_length:28 charset:255 flags:256 column_type:"enum('small','medium','large','xlarge','xxlarge')"} fields:{name:"hobbies" type:SET table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"hobbies" column_length:288 charset:255 flags:2048 column_type:"set('knitting','cooking','pickleball','biking','hiking','motorcycle','video games','reading')"} keyspace:"commerce" shard:"0" enum_set_string_values:true} keyspace:"commerce" shard:"0"]
[type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/156f702a-0d47-11ef-8723-653d045ab990:1-50"}} keyspace:"commerce" shard:"0"]
[type:ROW row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:9 lengths:6 lengths:15 values:"1Billy Bobxlargecooking,reading"}} keyspace:"commerce" shard:"0"} keyspace:"commerce" shard:"0" type:ROW row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:9 lengths:6 lengths:23 values:"2Sally Maemediumknitting,cooking,hiking"}} keyspace:"commerce" shard:"0"} keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/156f702a-0d47-11ef-8723-653d045ab990:1-50" table_p_ks:{table_name:"enum_set_test" lastpk:{fields:{name:"id" type:INT32 charset:63 flags:49667} rows:{lengths:1 values:"2"}}}}} keyspace:"commerce" shard:"0" type:COMMIT keyspace:"commerce" shard:"0"]
[type:BEGIN keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/156f702a-0d47-11ef-8723-653d045ab990:1-50"}} keyspace:"commerce" shard:"0" type:COMMIT keyspace:"commerce" shard:"0"]
[type:COPY_COMPLETED keyspace:"commerce" shard:"0" type:COPY_COMPLETED]
[type:BEGIN timestamp:1715179399 current_time:1715179399817221000 keyspace:"commerce" shard:"0" type:FIELD timestamp:1715179399 field_event:{table_name:"commerce.enum_set_test" fields:{name:"id" type:INT32 table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"id" column_length:11 charset:63 flags:49667 column_type:"int"} fields:{name:"name" type:VARCHAR table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"name" column_length:480 charset:255 column_type:"varchar(120)"} fields:{name:"shirt_size" type:ENUM table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"shirt_size" column_length:28 charset:255 flags:256 column_type:"enum('small','medium','large','xlarge','xxlarge')"} fields:{name:"hobbies" type:SET table:"enum_set_test" org_table:"enum_set_test" database:"vt_commerce" org_name:"hobbies" column_length:288 charset:255 flags:2048 column_type:"set('knitting','cooking','pickleball','biking','hiking','motorcycle','video games','reading')"} keyspace:"commerce" shard:"0" enum_set_string_values:true} current_time:1715179399821735000 keyspace:"commerce" shard:"0" type:ROW timestamp:1715179399 row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:9 lengths:6 lengths:55 values:"3Matt Lordmediumpickleball,biking,hiking,motorcycle,video games,reading"}} keyspace:"commerce" shard:"0" flags:1} current_time:1715179399821762000 keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/156f702a-0d47-11ef-8723-653d045ab990:1-51"}} keyspace:"commerce" shard:"0" type:COMMIT timestamp:1715179399 current_time:1715179399821801000 keyspace:"commerce" shard:"0"]
[type:BEGIN timestamp:1715179399 current_time:1715179399822310000 keyspace:"commerce" shard:"0" type:ROW timestamp:1715179399 row_event:{table_name:"commerce.enum_set_test" row_changes:{after:{lengths:1 lengths:15 lengths:5 lengths:0 values:"4Jerry Badyellowlarge"}} keyspace:"commerce" shard:"0" flags:1} current_time:1715179399822355000 keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/156f702a-0d47-11ef-8723-653d045ab990:1-52"}} keyspace:"commerce" shard:"0" type:COMMIT timestamp:1715179399 current_time:1715179399822360000 keyspace:"commerce" shard:"0"]
[type:BEGIN timestamp:1715179400 current_time:1715179400512056000 keyspace:"commerce" shard:"0" type:ROW timestamp:1715179400 row_event:{table_name:"commerce.enum_set_test" row_changes:{before:{lengths:1 lengths:9 lengths:6 lengths:23 values:"2Sally Maemediumknitting,cooking,hiking"} after:{lengths:1 lengths:9 lengths:5 lengths:31 values:"2Sally Maesmallknitting,cooking,hiking,reading"}} keyspace:"commerce" shard:"0" flags:1} current_time:1715179400512094000 keyspace:"commerce" shard:"0" type:VGTID vgtid:{shard_gtids:{keyspace:"commerce" shard:"0" gtid:"MySQL56/156f702a-0d47-11ef-8723-653d045ab990:1-53"}} keyspace:"commerce" shard:"0" type:COMMIT timestamp:1715179400 current_time:1715179400512108000 keyspace:"commerce" shard:"0"]

An example key difference there being that after:{lengths:1 lengths:9 lengths:1 lengths:3 values:"2Sally Mae1147"} from Vitess v19 and older becomes after:{lengths:1 lengths:9 lengths:5 lengths:31 values:"2Sally Maesmallknitting,cooking,hiking,reading"} from Vitess v20 and newer. So 1 -> small and 147 -> knitting,cooking,hiking,reading for the ENUM and SET column values respectively. This also demonstrates why this mapping is necessary in consumers/clients, as 147 has no logical meaning/value for this column outside of MySQL internals.

If you're using the Debezium Vitess connector, you should upgrade your connector to 2.7 (the next release) — which should contain the relevant necessary changes — prior to upgrading Vitess to v20.0.1 or later. If you're using any of the PlanetScale connectors (AirByte, FiveTran, or singer-tap) then no actions are required.

If you're using a custom VStream client/consumer, then you will need to build a new client with the updated v20 binlogdata protos (source for which would be in main or the release-20.0 branch) before needing to support Vitess v20.0.1 or later. Your client will then be able to handle old and new messages, with older messages always having this new field set to false.

`shutdown_grace_period` Default Change

The --shutdown_grace_period flag, which was introduced in v2 with a default of 0 seconds, has now been changed to default to 3 seconds.
This makes reparenting in Vitess resilient to client errors, and prevents PlannedReparentShard from timing out.

In order to preserve the old behaviour, the users can set the flag back to 0 seconds causing open transactions to never be shutdown, but in that case, they run the risk of PlannedReparentShard calls timing out.

New `unmanaged` Flag and `disable_active_reparents` deprecation

New flag --unmanaged has been introduced in this release to make it easier to flag unmanaged tablets. It also runs validations to make sure the unmanaged tablets are configured properly. --disable_active_reparents flag has been deprecated for vttablet, vtcombo and vttestserver binaries and will be removed in future releases. Specifying the --unmanaged flag will also block replication commands and replication repairs.

Starting this release, all unmanaged tablets should specify this flag.

`recovery-period-block-duration` Flag deprecation

The flag --recovery-period-block-duration has been deprecated in VTOrc from this release. Its value is now ignored and the flag will be removed in later releases.
VTOrc no longer blocks recoveries for a certain duration after a previous recovery has completed. Since VTOrc refreshes the required information after
acquiring a shard lock, blocking of recoveries is not required.

`mysqlctld` `onterm_timeout` Default Change

The --onterm_timeout flag default value has changed for mysqlctld. It now is by default long enough to be able to wait for the default --shutdown-wait-time when shutting down on a TERM signal.

This is necessary since otherwise MySQL would never shut down cleanly with the old defaults, since mysqlctld would shut down already after 10 seconds by default.

`MoveTables` now removes `auto_increment` clauses by default when moving tables from an unsharded keyspace to a sharded one

A new --remove-sharded-auto-increment flag has been added to the MoveTables create sub-command and it is set to true by default. This flag controls whether any MySQL auto_increment clauses should be removed from the table definitions when moving tables from an unsharded keyspace to a sharded one. This is now done by default as auto_increment clauses should not typically be used with sharded tables and you should instead rely on externally generated values such as a form of universally/globally unique identifiers or use Vitess sequences in order to ensure that each row has a unique identifier (Primary Key value) across all shards. If for some reason you want to retain them you can set this new flag to false when creating the workflow.

`Durabler` interface method renaming

The methods of the Durabler interface in go/vt/vtctl/reparentutil were renamed to be public (capitalized) methods to make it easier to integrate custom Durability Policies from external packages. See RFC for details.

Users of custom Durability Policies must rename private Durabler methods.

Changes:

The promotionRule method was renamed to PromotionRule
The semiSyncAckers method was renamed to SemiSyncAckers
The isReplicaSemiSync method was renamed to IsReplicaSemiSync

Query Compatibility

Vindex Hints

Vitess now supports Vindex hints that provide a way for users to influence the shard routing of queries in Vitess by specifying, which vindexes should be considered or ignored by the query planner. This feature enhances the control over query execution, allowing for potentially more efficient data access patterns in sharded databases.

Example:

   SELECT * FROM user USE VINDEX (hash_user_id, secondary_vindex) WHERE user_id = 123;
   SELECT * FROM order IGNORE VINDEX (range_order_id) WHERE order_date = '2021-01-01';

For more information about Vindex hints and its usage, please consult the documentation.

Update with Limit Support

Support is added for sharded update with limit.

Example: update t1 set t1.foo = 'abc', t1.bar = 23 where t1.baz > 5 limit 1

More details about how it works is available in MySQL Docs

Update with Multi Table Support

Support is added for sharded multi-table update with column update on single target table using multiple table join.

Example: update t1 join t2 on t1.id = t2.id join t3 on t1.col = t3.col set t1.baz = 'abc', t1.apa = 23 where t3.foo = 5 and t2.bar = 7

More details about how it works is available in MySQL Docs

Update with Multi Target Support

Support is added for sharded multi table target update.

Example: update t1 join t2 on t1.id = t2.id set t1.foo = 'abc', t2.bar = 23

More details about how it works is available in MySQL Docs

Delete with Subquery Support

Support is added for sharded table delete with subquery

Example: delete from t1 where id in (select col from t2 where foo = 32 and bar = 43)

Delete with Multi Target Support

Support is added for sharded multi table target delete.

Example: delete t1, t3 from t1 join t2 on t1.id = t2.id join t3 on t1.col = t3.col

More details about how it works is available in MySQL Docs

User Defined Functions Support

VTGate can track any user defined functions for better planning.
User Defined Functions (UDFs) should be directly loaded in the underlying MySQL.

It should be enabled in VTGate with the --track-udfs flag.
This will enable the tracking of UDFs in VTGate and will be used for planning.
Without this flag, VTGate will not be aware that there might be aggregating user-defined functions in the query that need to be pushed down to MySQL.

More details about how to load UDFs is available in MySQL Docs

Insert Row Alias Support

Support is added to have row alias in Insert statement to be used with on duplicate key update.

Example:

insert into user(id, name, email) valies (100, 'Alice', '[email protected]') as new on duplicate key update name = new.name, email = new.email
insert into user(id, name, email) valies (100, 'Alice', '[email protected]') as new(m, n, p) on duplicate key update name = n, email = p

More details about how it works is available in MySQL Docs

Query Timeout

On a query timeout, Vitess closed the connection using the kill connection statement. This leads to connection churn
which is not desirable in some cases. To avoid this, Vitess now uses the kill query statement to cancel the query.
This will only cancel the query and does not terminate the connection.

Flag Changes

`pprof-http` Default Change

The --pprof-http flag, which was introduced in v19 with a default of true, has now been changed to default to false.
This makes HTTP pprof endpoints now an opt-in feature, rather than opt-out.
To continue enabling these endpoints, explicitly set --pprof-http when starting up Vitess components.

New `--healthcheck-dial-concurrency` flag

The new --healthcheck-dial-concurrency flag defines the maximum number of healthcheck connections that can open concurrently. This limit is to avoid hitting Go runtime panics on deployments watching enough tablets to hit the runtime's maximum thread limit of 10000 due to blocking network syscalls. This flag applies to vtcombo, vtctld and vtgate only and a value less than the runtime max thread limit (10000) is recommended.

New minimum for `--buffer_min_time_between_failovers`

The --buffer_min_time_between_failovers vttablet flag now has a minimum value of 1s. This is because a value of 0 can cause issues with the buffering mechanics resulting in unexpected and unnecessary query errors — in particular during MoveTables SwitchTraffic operations. If you are currently specifying a value of 0 for this flag then you will need to update the config value to 1s prior to upgrading to v20 or later as vttablet will report an error and terminate if you attempt to start it with a value of 0.

New `--track-udfs` vtgate flag

The new --track-udfs flag enables VTGate to track user defined functions for better planning.

Help text fix for `--lock-timeout`

The help text for the flag --lock-timeout was incorrect. We were documenting it as a flag that controlled the duration for which the shard lock was acquired. It is actually the maximum duration for which we wait while attempting to acquire a lock from the topology server.

New `--querylog-sample-rate` flag

The new flag --querylog-sample-rate float adds support for sampling queries based on a float value between 0.0 (no logging) and 1.0 (all queries logged). If configured, this filtering is applied after the existing --querylog-filter-tag filter.

New `--tablet-filter-tags` flag

The new flag --tablet-filter-tags StringMap adds support to VTGate for filtering tablets by tablet tag key/values, specified as comma-separated list of key:values. The tags of a tablet are defined by the VTTablet flag --init_tags, which is also defined as a comma-separated list of key:values.

Minor Changes

New Stats

VTTablet Query Cache Hits and Misses

VTTablet exposes two new counter stats:

QueryCacheHits: Query engine query cache hits
QueryCacheMisses: Query engine query cache misses

VTTablet Query Text Characters Processed

VTGate and VTTablet expose a new counter stat QueryTextCharactersProcessed to reflect the number of query text characters processed.

VTGate groups this metric by Operation, Keyspace and TabletType. On VTTablet it is grouped by Table, Plan and optionally Workload.

`SIGHUP` reload of gRPC client static auth creds

The internal gRPC client now caches the static auth credentials and supports reloading via the SIGHUP signal. Previous to v20 the credentials were not cached. They were re-loaded from disk on every use.

VTAdmin

vtadmin-web updated to node v20.12.2 (LTS)

Building vtadmin-web now requires node >= v20.12.0 (LTS). Breaking changes from v18 to v20 can be found at https://nodejs.org/en/blog/release/v20.12.0 -- with no known issues that apply to VTAdmin.
Full details on the node v20.12.2 release can be found at https://nodejs.org/en/blog/release/v20.12.2.

Replaced highcharts with d3

The vtadmin-web UI no longer has a dependency on highcharts for licensing reasons. The tablet QPS, tablet VReplication QPS, and workflow streams lag charts have all been replaced by d3. We'll be iteratively improving the d3 charts until they reach feature parity with the original highcharts charts.

Vitess v20.0.0

Release of Vitess v20.0.0

Summary

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