OnlineDDL: Revert for VReplication based migrations by shlomi-noach · Pull Request #7478 · vitessio/vitess

shlomi-noach · 2021-02-10T10:08:54Z

Ready for review

This PR offers lossless revert for online DDL. Revert is supported for:

CREATE TABLE and DROP TABLE using any online `ddl_strategy` (either `online`, `gh-ost`, `pt-osc`):

CREATE TABLE : the revert is to DROP, but actually implemented by RENAME...
CREATE TABLE IF NOT EXISTS: if the CREATE was a noop, then so is the revert
DROP TABLE: online DDL implements DRPO via RENANE. Revert "creates" the table by renaming it back into place
DROP TABLE IF EXISTS: if the DROP was a noop then so is the revert

ALTER TABLE using `ddl_strategy=online`

Only VReplication-based ALTER migrations are revertible.

Any reverted migration

It is possible to revert reverted migration, reverted-reverted migrations, and it's turtles all the way down.

Eligible migrations

On top of the above constraints, you may only revert a migration if:

It is the last successful migration to run on a table.

At this time we only support revert for the last migration, which means you cannot revert the migrations 2nd before last, and you can't "pop" the stack of migrations. However, notice that when you revert a migraiton, the revert itself is a (hopefully) succesful migration, and you may revert the revert.

What's in a revert?

A revert is an online schema migration of its own. You may submit a revert via vtctl OnlineDDL <keyspace> revert <uuid>. This generates a new UUID, which is the job ID for the new revert migration.

Revert migrations are queued and scheduled same as any other migration. They can be tracked, cancelled and retried same as any other migration.

A revert migration is indicated by a SQL statement of the form revert fb697374_7b25_11eb_85f4_f875a4d24e90. This statement is internal and not supported in VTGate or in any MySQL connection. Work in progress for specialized SQL syntax.

It's important to note that a revert migration does not modify the entry for the migration it reverts. It reads the details of the reverted migration from _vt.schema_migrations, and, since it is a migration in itself, has its own entry in that table.

Implementation

The revert implementation for CREATE and DROP is relatively simple, in the form of counter-queries that revert the effects of the original migraiton. A revert never actually CREATEs a table, and never actually DROPs a table. It's implemented behind the scenes by RENAMEs. There is special logic to handle the case for CREATE TABLE IF NOT EXISTS and DROP TABLE IF EXISTS.

The implementation for ALTER, with ddl_strategy='online' is more elaborate, and includes:

Finding the artifact table from the to-be-reverted ALTER migration
Finding the _vt.vreplication entry from the to-be-reverted ALTER migration
Sanity checks
Re-evaluate a VReplication rule/filter for the new migration
Read the pos from the to-be-reverted VReplication stream. That pos was taken while tables were swapped and while no writes took place on the table.
Construct a new VReplication stream from the above.
Run the new migration.

We use the artifacts value in _vt.schema_migration to identify what the original table was.

Lossless

The user has 24 hours to revert a migration without losing data.

When you revert a DROP, the table reappears with all data intact.
When you revert an ALTER, VReplication makes sure to apply any changes made to the table following the migration, so that you do not lose data.
- This assumes the new table did not receive changes which are irrevertible. For example, you may have altered a VARCHAR(10) to VARCHAR(20). If the new table was populated with now longer texts, then it is irrevertible.
- Revert-the-revert, revert-the-revert-the-revert and so forth are likewise lossless.

Tests

Online DDL Revert is tested via a specialize endtoend test. See below to get a sense of what gets tested:

--- PASS: TestSchemaChange (525.06s)
    --- PASS: TestSchemaChange/CREATE_TABLE_IF_NOT_EXISTS_where_table_does_not_exist (20.04s)
    --- PASS: TestSchemaChange/revert_CREATE_TABLE_IF_NOT_EXISTS_where_did_not_exist (20.05s)
    --- PASS: TestSchemaChange/revert_revert_CREATE_TABLE_IF_NOT_EXISTS_where_did_not_exist (20.05s)
    --- PASS: TestSchemaChange/revert_revert_revert_CREATE_TABLE_IF_NOT_EXISTS_where_did_not_exist (20.05s)
    --- PASS: TestSchemaChange/online_CREATE_TABLE (23.55s)
    --- PASS: TestSchemaChange/revert_CREATE_TABLE (20.05s)
    --- PASS: TestSchemaChange/revert_revert_CREATE_TABLE (20.05s)
    --- PASS: TestSchemaChange/fail_revert_older_change (20.05s)
    --- PASS: TestSchemaChange/CREATE_TABLE_IF_NOT_EXISTS_where_table_exists (20.04s)
    --- PASS: TestSchemaChange/revert_CREATE_TABLE_IF_NOT_EXISTS_where_table_existed (20.05s)
    --- PASS: TestSchemaChange/revert_revert_CREATE_TABLE_IF_NOT_EXISTS_where_table_existed (20.06s)
    --- PASS: TestSchemaChange/fail_online_CREATE_TABLE (20.05s)
    --- PASS: TestSchemaChange/online_ALTER_TABLE_0 (20.07s)
    --- PASS: TestSchemaChange/online_ALTER_TABLE_1 (20.07s)
    --- PASS: TestSchemaChange/revert_ALTER_TABLE (20.09s)
    --- PASS: TestSchemaChange/revert_revert_ALTER_TABLE (20.08s)
    --- PASS: TestSchemaChange/revert_revert_revert_ALTER_TABLE (20.09s)
    --- PASS: TestSchemaChange/online_DROP_TABLE (20.04s)
    --- PASS: TestSchemaChange/revert_DROP_TABLE (20.07s)
    --- PASS: TestSchemaChange/revert_revert_DROP_TABLE (20.06s)
    --- PASS: TestSchemaChange/online_DROP_TABLE_IF_EXISTS (20.07s)
    --- PASS: TestSchemaChange/revert_DROP_TABLE_IF_EXISTS (20.08s)
    --- PASS: TestSchemaChange/revert_revert_DROP_TABLE_IF_EXISTS (20.07s)
    --- PASS: TestSchemaChange/revert_revert_revert_DROP_TABLE_IF_EXISTS (20.07s)
    --- PASS: TestSchemaChange/fail_online_DROP_TABLE (20.07s)
    --- PASS: TestSchemaChange/fail_revert_failed_online_DROP_TABLE (20.07s)
PASS

Points of interest for the reviewer

go/test/endtoend/onlineddl_revert/onlineddl_revert_test.go is the endtoend test, and should give some clarity on general behavior.
In go/vt/vtctl/vtctl.go (https://github.com/vitessio/vitess/pull/7478/files#diff-ad37010accc5a29c6751d18124328bb882457e8b2527db688b854c81fe23861c), you can see how a revert <UUID> is constructed, and sent just as if it were a normal migration.
Everything that is important is in go/vt/vttablet/onlineddl/executor.go, https://github.com/vitessio/vitess/pull/7478/files#diff-ad37010accc5a29c6751d18124328bb882457e8b2527db688b854c81fe23861c
- initVreplicationOriginalMigration(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R584 is where we init a vreplication DDL for a new ALTER (this code existsed before but now refactored into a separate function), and:
- initVreplicationRevertMigration(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R605 is where we inita vreplication DDL which is a revert for a previous VReplication migration. This is where we read the details of the soon-to-be-reverted migration, and speicifcally table & pos.
- validateMigrationRevertible(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R1310, is th elogic where we verify the migration we revert is the last successful one on the given table, etc.
- executeRevert(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R1376, is where all reverts happen. For ALTER, the function quickly delegates to vreplication-specific handling. For CREATE and DROP the logic is within this function. There's a lot of logic to handle edge cases, IF EXISTS, IF NOT EXISTS etc.

Original comment, when this PR was just WIP:

This PR extends #7419 . It only makes sense to review it after #7419 is reviewed & merged.

This experimental PR introduces revert for Online DDL via VReplicaiton. With this PR it is possible to revert a successfully completed DDL performed by VReplication on a table (where this was tha last migration executed on said table). The revert operation may take place for as long as the old table is still available, which is now set to 24h.

This is still evolving, more writeup coming later.

Related Issue(s)

extends Online DDL via VReplication #7419
tracking: Online DDL: tracking issue #6926

Checklist

Should this PR be backported?
Tests were added or are not required
Documentation was added or is not required

Deployment Notes

Impacted Areas in Vitess

Components that this PR will affect:

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

…evert Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

…cessful migration on the table, and that there's no pending migrations on that table Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

shlomi-noach · 2021-02-16T05:04:25Z

Convenience link to track changes on top of vreplication-online-ddl branch (#7419): planetscale/vitess@vreplication-online-ddl...vreplication-online-ddl-revert

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

…tatements Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

…evert Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

…not originally exist Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

…R and DROP Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

…-retries is impractical Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

shlomi-noach · 2021-03-02T12:00:53Z

Ready for review

This PR offers lossless revert for online DDL. Revert is supported for:

CREATE TABLE and DROP TABLE using any online `ddl_strategy` (either `online`, `gh-ost`, `pt-osc`):

CREATE TABLE : the revert is to DROP, but actually implemented by RENAME...
CREATE TABLE IF NOT EXISTS: if the CREATE was a noop, then so is the revert
DROP TABLE: online DDL implements DRPO via RENANE. Revert "creates" the table by renaming it back into place
DROP TABLE IF EXISTS: if the DROP was a noop then so is the revert

ALTER TABLE using `ddl_strategy=online`

Only VReplication-based ALTER migrations are revertible.

Any reverted migration

It is possible to revert reverted migration, reverted-reverted migrations, and it's turtles all the way down.

Eligible migrations

On top of the above constraints, you may only revert a migration if:

It is the last successful migration to run on a table.

At this time we only support revert for the last migration, which means you cannot revert the migrations 2nd before last, and you can't "pop" the stack of migrations. However, notice that when you revert a migraiton, the revert itself is a (hopefully) succesful migration, and you may revert the revert.

What's in a revert?

A revert is an online schema migration of its own. You may submit a revert via vtctl OnlineDDL <keyspace> revert <uuid>. This generates a new UUID, which is the job ID for the new revert migration.

Revert migrations are queued and scheduled same as any other migration. They can be tracked, cancelled and retried same as any other migration.

A revert migration is indicated by a SQL statement of the form revert fb697374_7b25_11eb_85f4_f875a4d24e90. This statement is internal and not supported in VTGate or in any MySQL connection. Work in progress for specialized SQL syntax.

It's important to note that a revert migration does not modify the entry for the migration it reverts. It reads the details of the reverted migration from _vt.schema_migrations, and, since it is a migration in itself, has its own entry in that table.

Implementation

The revert implementation for CREATE and DROP is relatively simple, in the form of counter-queries that revert the effects of the original migraiton. A revert never actually CREATEs a table, and never actually DROPs a table. It's implemented behind the scenes by RENAMEs. There is special logic to handle the case for CREATE TABLE IF NOT EXISTS and DROP TABLE IF EXISTS.

The implementation for ALTER, with ddl_strategy='online' is more elaborate, and includes:

Finding the artifact table from the to-be-reverted ALTER migration
Finding the _vt.vreplication entry from the to-be-reverted ALTER migration
Sanity checks
Re-evaluate a VReplication rule/filter for the new migration
Read the pos from the to-be-reverted VReplication stream. That pos was taken while tables were swapped and while no writes took place on the table.
Construct a new VReplication stream from the above.
Run the new migration.

We use the artifacts value in _vt.schema_migration to identify what the original table was.

Lossless

The user has 24 hours to revert a migration without losing data.

When you revert a DROP, the table reappears with all data intact.
When you revert an ALTER, VReplication makes sure to apply any changes made to the table following the migration, so that you do not lose data.
- This assumes the new table did not receive changes which are irrevertible. For example, you may have altered a VARCHAR(10) to VARCHAR(20). If the new table was populated with now longer texts, then it is irrevertible.
- Revert-the-revert, revert-the-revert-the-revert and so forth are likewise lossless.

Tests

Online DDL Revert is tested via a specialize endtoend test. See below to get a sense of what gets tested:

--- PASS: TestSchemaChange (525.06s)
    --- PASS: TestSchemaChange/CREATE_TABLE_IF_NOT_EXISTS_where_table_does_not_exist (20.04s)
    --- PASS: TestSchemaChange/revert_CREATE_TABLE_IF_NOT_EXISTS_where_did_not_exist (20.05s)
    --- PASS: TestSchemaChange/revert_revert_CREATE_TABLE_IF_NOT_EXISTS_where_did_not_exist (20.05s)
    --- PASS: TestSchemaChange/revert_revert_revert_CREATE_TABLE_IF_NOT_EXISTS_where_did_not_exist (20.05s)
    --- PASS: TestSchemaChange/online_CREATE_TABLE (23.55s)
    --- PASS: TestSchemaChange/revert_CREATE_TABLE (20.05s)
    --- PASS: TestSchemaChange/revert_revert_CREATE_TABLE (20.05s)
    --- PASS: TestSchemaChange/fail_revert_older_change (20.05s)
    --- PASS: TestSchemaChange/CREATE_TABLE_IF_NOT_EXISTS_where_table_exists (20.04s)
    --- PASS: TestSchemaChange/revert_CREATE_TABLE_IF_NOT_EXISTS_where_table_existed (20.05s)
    --- PASS: TestSchemaChange/revert_revert_CREATE_TABLE_IF_NOT_EXISTS_where_table_existed (20.06s)
    --- PASS: TestSchemaChange/fail_online_CREATE_TABLE (20.05s)
    --- PASS: TestSchemaChange/online_ALTER_TABLE_0 (20.07s)
    --- PASS: TestSchemaChange/online_ALTER_TABLE_1 (20.07s)
    --- PASS: TestSchemaChange/revert_ALTER_TABLE (20.09s)
    --- PASS: TestSchemaChange/revert_revert_ALTER_TABLE (20.08s)
    --- PASS: TestSchemaChange/revert_revert_revert_ALTER_TABLE (20.09s)
    --- PASS: TestSchemaChange/online_DROP_TABLE (20.04s)
    --- PASS: TestSchemaChange/revert_DROP_TABLE (20.07s)
    --- PASS: TestSchemaChange/revert_revert_DROP_TABLE (20.06s)
    --- PASS: TestSchemaChange/online_DROP_TABLE_IF_EXISTS (20.07s)
    --- PASS: TestSchemaChange/revert_DROP_TABLE_IF_EXISTS (20.08s)
    --- PASS: TestSchemaChange/revert_revert_DROP_TABLE_IF_EXISTS (20.07s)
    --- PASS: TestSchemaChange/revert_revert_revert_DROP_TABLE_IF_EXISTS (20.07s)
    --- PASS: TestSchemaChange/fail_online_DROP_TABLE (20.07s)
    --- PASS: TestSchemaChange/fail_revert_failed_online_DROP_TABLE (20.07s)
PASS

Points of interest for the reviewer

go/test/endtoend/onlineddl_revert/onlineddl_revert_test.go is the endtoend test, and should give some clarity on general behavior.
In go/vt/vtctl/vtctl.go (https://github.com/vitessio/vitess/pull/7478/files#diff-ad37010accc5a29c6751d18124328bb882457e8b2527db688b854c81fe23861c), you can see how a revert <UUID> is constructed, and sent just as if it were a normal migration.
Everything that is important is in go/vt/vttablet/onlineddl/executor.go, https://github.com/vitessio/vitess/pull/7478/files#diff-ad37010accc5a29c6751d18124328bb882457e8b2527db688b854c81fe23861c
- initVreplicationOriginalMigration(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R584 is where we init a vreplication DDL for a new ALTER (this code existsed before but now refactored into a separate function), and:
- initVreplicationRevertMigration(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R605 is where we inita vreplication DDL which is a revert for a previous VReplication migration. This is where we read the details of the soon-to-be-reverted migration, and speicifcally table & pos.
- validateMigrationRevertible(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R1310, is th elogic where we verify the migration we revert is the last successful one on the given table, etc.
- executeRevert(), https://github.com/vitessio/vitess/pull/7478/files#diff-059c9f46e8d270d9c5514ef2b08679035eb0daaa8d95074e34ef43a81d50dc37R1376, is where all reverts happen. For ALTER, the function quickly delegates to vreplication-specific handling. For CREATE and DROP the logic is within this function. There's a lot of logic to handle edge cases, IF EXISTS, IF NOT EXISTS etc.

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

GuptaManan100

LGTM!! 🚀

rohit-nayak-ps

this is brilliant :-)

rohit-nayak-ps · 2021-03-06T09:55:19Z

go/test/endtoend/onlineddl_revert/onlineddl_revert_test.go

@@ -0,0 +1,776 @@
+/*
+Copyright 2019 The Vitess Authors.


copyright: 2021?

rohit-nayak-ps · 2021-03-06T10:04:20Z

go/test/endtoend/onlineddl_revert/onlineddl_revert_test.go

+		testSelectTableMetrics(t)
+	})
+	t.Run("fail revert older change", func(t *testing.T) {
+		// We shouldn't be able to revert one-before-last succcessfulk migration.


succcessfulk=>successful

rohit-nayak-ps · 2021-03-06T10:55:03Z

go/test/endtoend/onlineddl_revert/onlineddl_revert_test.go

+	fmt.Println("# 'vtctlclient OnlineDDL show recent' output (for debug purposes):")
+	fmt.Println(result)
+	assert.Equal(t, len(clusterInstance.Keyspaces[0].Shards), strings.Count(result, uuid))
+	// We ensure "full word" regexp becuase some column names may conflict


becuase=>because

rohit-nayak-ps · 2021-03-06T10:59:15Z

go/vt/schema/online_ddl.go

+
+// GetRevertUUID works when this migration is a revert for another migration. It returns the UUID
+// fo the reverted migration.
+// The functio nreturns error when this is not a revert migration.


functio nreturns =>function returns an

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

shlomi-noach added 3 commits February 8, 2021 15:21

revert migration

f8274b7

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

retain ddl tables: applies to all migration types

a866ceb

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Merge branch 'vreplication-online-ddl' into vreplication-online-ddl-r…

86e8885

…evert Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

shlomi-noach changed the title ~~Vreplication online ddl revert~~ OnlineDDL: Revert for VReplication based migrations Feb 10, 2021

shlomi-noach added 2 commits February 10, 2021 14:40

sanity checks: varify the migration we wish to revert is the last suc…

71bbb40

…cessful migration on the table, and that there's no pending migrations on that table Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

endtoend test: validate table data is as expected

d84f1be

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

shlomi-noach added 12 commits February 18, 2021 14:50

online DROP TABLE: update artifacts with renamed table

f5fdcee

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

revert: generalizing the logic to support reverting CREATE and DROP s…

e1dd8fc

…tatements Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Merge branch 'vreplication-online-ddl' into vreplication-online-ddl-r…

68f3104

…evert Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

handle revert sequence for DROP TABLE IF EXISTS, where the table did …

8a8096a

…not originally exist Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

endtoend tests for online DDL revert, testing revert for CREATE, ALTE…

389c859

…R and DROP Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Merge branch 'master' into vreplication-online-ddl-revert

e4c7102

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

endtoend tests can fail on setting up vttablet. My idea for having no…

dcdc2cf

…-retries is impractical Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

normalize json

548818d

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

Merge branch 'master' into vreplication-online-ddl-revert

44a5ff9

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

handle CREATE TABLE IF NOT EXISTS scenarios

a3b1a4b

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

endtoend tests for CREATE TABLE IF NOT EXISTS scenarios

7abf2b5

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

resolve conflict

3311be4

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

shlomi-noach marked this pull request as ready for review March 2, 2021 12:02

shlomi-noach requested review from GuptaManan100, ajm188, doeg, harshit-gangal, sougou and systay as code owners March 2, 2021 12:02

shlomi-noach requested a review from rohit-nayak-ps March 2, 2021 12:02

shlomi-noach mentioned this pull request Mar 2, 2021

Online DDL: tracking issue #6926

Open

merge master

8f671c7

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

GuptaManan100 approved these changes Mar 3, 2021

View reviewed changes

shlomi-noach mentioned this pull request Mar 4, 2021

Suggestions for online DDL query syntax #7604

Closed

rohit-nayak-ps approved these changes Mar 6, 2021

View reviewed changes

typos fixed per review

924d13b

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

shlomi-noach requested a review from deepthi as a code owner March 7, 2021 06:46

shlomi-noach merged commit 5174643 into vitessio:master Mar 7, 2021

shlomi-noach deleted the vreplication-online-ddl-revert branch March 7, 2021 07:33

shlomi-noach mentioned this pull request Mar 10, 2021

Support for REVERT VITESS_MIGRATION statement #7656

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askdba added Component: VReplication Component: Query Serving labels Mar 10, 2021

askdba added this to the v10.0 milestone Mar 10, 2021

shlomi-noach mentioned this pull request Mar 25, 2021

Online DDL: revertible migrations, declarative migrations, SQL commands vitessio/website#733

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ajm188 mentioned this pull request Jul 15, 2021

slack vitess v10.pre tinyspeck/vitess#228

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shlomi-noach mentioned this pull request Jun 30, 2024

Online DDL: remove legacy (and ancient) 'REVERT <uuid>' syntax #16301

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OnlineDDL: Revert for VReplication based migrations#7478

OnlineDDL: Revert for VReplication based migrations#7478
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shlomi-noach commented Feb 10, 2021 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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CREATE TABLE and DROP TABLE using any online ddl_strategy (either online, gh-ost, pt-osc):

ALTER TABLE using ddl_strategy=online

Any reverted migration

Eligible migrations

What's in a revert?

Implementation

Lossless

Tests

Points of interest for the reviewer

Original comment, when this PR was just WIP:

Related Issue(s)

Checklist

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Impacted Areas in Vitess

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shlomi-noach commented Feb 16, 2021

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shlomi-noach commented Mar 2, 2021

Ready for review

CREATE TABLE and DROP TABLE using any online ddl_strategy (either online, gh-ost, pt-osc):

ALTER TABLE using ddl_strategy=online

Any reverted migration

Eligible migrations

What's in a revert?

Implementation

Lossless

Tests

Points of interest for the reviewer

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shlomi-noach commented Feb 10, 2021 •

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CREATE TABLE and DROP TABLE using any online `ddl_strategy` (either `online`, `gh-ost`, `pt-osc`):

ALTER TABLE using `ddl_strategy=online`

CREATE TABLE and DROP TABLE using any online `ddl_strategy` (either `online`, `gh-ost`, `pt-osc`):

ALTER TABLE using `ddl_strategy=online`