add skip isolation level check variable by marsishandsome · Pull Request #10065 · pingcap/tidb

marsishandsome · 2019-04-08T07:05:39Z

What problem does this PR solve?

This patch (https://github.com/pingcap/tidb/pull/8625/files) breaks backward compatible.
When using tidb as hive's metastore, hive will set transaction isolation level to serializable, which will cause the following error:

ERROR 1105 (HY000): variable 'tx_isolation' does not yet support value: SERIALIZABLE

What is changed and how it works?

This PR provide a variable tidb_skip_isolation_level_check.
If tidb_skip_isolation_level_check == ON, tidb will not throw an error if hive call set session transaction isolation level serializable;. tidb_skip_isolation_level_check's default value is OFF.

Check List

Tests

Unit test

Related changes

Need to be included in the release note
Need to cherry-pick to the release branch

CLAassistant · 2019-04-08T07:05:46Z

All committers have signed the CLA.

marsishandsome · 2019-04-08T09:01:45Z

/run-all-tests

codecov · 2019-04-08T09:31:52Z

Codecov Report

❗ No coverage uploaded for pull request base (master@ee99570). Click here to learn what that means.
The diff coverage is 35.7142%.

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marsishandsome · 2019-04-08T13:52:18Z

/run-all-tests

marsishandsome · 2019-04-08T15:10:41Z

/run-all-tests

marsishandsome · 2019-04-08T15:12:00Z

/run-all-tests

marsishandsome · 2019-04-08T15:35:22Z

@jackysp @zhexuany please review

morgo · 2019-04-08T16:45:14Z

@marsishandsome thank you for looking into this. I would like to suggest that we don't call it strict, since in other MySQL contexts strict means "more safe". Here it means "less safe" because an error is downgraded.

The MySQL-like name for this would be "ignore" or "skip". I would also prefer to have a purposeful name here, because it is a very specific feature being disabled which is unsafe (versus a generic name, which may be better if they are just general changes).

So perhaps skip-isolation-level-checks?

PTAL @kolbe

zhexuany · 2019-04-08T16:48:24Z

@morgo Agreed. I guess the intention of tidb_strict_compatibility is that when it on throws an error on unsupported isolation level. skip_isolation_level_check maybe a better name. /cc @marsishandsome WDUT?

marsishandsome · 2019-04-11T02:52:43Z

@morgo @jackysp PTAL

morgo · 2019-04-11T03:12:15Z

+	tk.MustExec("SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE")
+	tk.MustQuery("show warnings").Check(testkit.Rows(
+		"Warning 1105 The isolation level 'SERIALIZABLE' is not supported. Set tidb_skip_isolation_level_check=1 to skip this error",
+		"Warning 1105 The isolation level 'SERIALIZABLE' is not supported. Set tidb_skip_isolation_level_check=1 to skip this error"))


I would like to see just one warning here.

@zhexuany @jackysp any suggestions about how to elegantly deduplicate two same warnings?

I think we should debug it, why the warning was appended twice.

SET TRANSACTION ISOLATION LEVEL will affect two internal variables:

tx_isolation

transaction_isolation

So the function ValidateSetSystemVar is called twice.

Because the error message does not mention which variable was set now, it is easy to fix by wrapping an if around transaction_isolation.

@morgo @jackysp PTAL again

morgo · 2019-04-11T03:12:21Z

+	tk.MustExec("SET GLOBAL TRANSACTION ISOLATION LEVEL READ UNCOMMITTED")
+	tk.MustQuery("show warnings").Check(testkit.Rows(
+		"Warning 1105 The isolation level 'READ-UNCOMMITTED' is not supported. Set tidb_skip_isolation_level_check=1 to skip this error",
+		"Warning 1105 The isolation level 'READ-UNCOMMITTED' is not supported. Set tidb_skip_isolation_level_check=1 to skip this error"))


And here too

morgo

LGTM

marsishandsome · 2019-04-11T04:32:06Z

/run-all-tests

marsishandsome · 2019-04-11T05:51:30Z

/run-all-tests

marsishandsome · 2019-04-11T07:38:24Z

/run-all-tests

zhexuany added status/WIP component/mysql-protocol component/session labels Apr 8, 2019

marsishandsome force-pushed the feature/strict_compatibility branch 4 times, most recently from c2e06f3 to 1a101fd Compare April 8, 2019 08:33

zhexuany reviewed Apr 8, 2019

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Comment thread sessionctx/variable/session.go Outdated

zhexuany reviewed Apr 8, 2019

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Comment thread sessionctx/variable/session.go Outdated

marsishandsome force-pushed the feature/strict_compatibility branch 4 times, most recently from c594105 to 6740581 Compare April 8, 2019 14:56

zhexuany removed the status/WIP label Apr 8, 2019

marsishandsome force-pushed the feature/strict_compatibility branch from 6740581 to aa16017 Compare April 8, 2019 15:07

marsishandsome added the status/WIP label Apr 8, 2019

marsishandsome force-pushed the feature/strict_compatibility branch from aa16017 to 9be5a55 Compare April 8, 2019 15:14

marsishandsome removed the status/WIP label Apr 8, 2019

marsishandsome assigned jackysp and zhexuany Apr 8, 2019

winkyao reviewed Apr 8, 2019

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Comment thread sessionctx/variable/varsutil.go Outdated

marsishandsome reopened this Apr 10, 2019

marsishandsome added 11 commits April 11, 2019 10:07

add strict compatibility variable

427762b

e -> err

3270cf5

make fmt

6579b58

add unit test

4271cd6

change tidb_strict_compatibility to tidb_skip_isolation_level_check

8d0a17d

fix log warning

8ddd5c5

fix error msg

4c5eddd

add warning check in ut

0bda114

fix ut

a388359

fix ut

18957ec

change error message

470b0dd

marsishandsome dismissed zhexuany’s stale review via 470b0dd April 11, 2019 02:07

marsishandsome force-pushed the feature/strict_compatibility branch from 514da01 to 470b0dd Compare April 11, 2019 02:07

morgo reviewed Apr 11, 2019

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deduplicate two same warnings

2c75356

morgo reviewed Apr 11, 2019

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jackysp added the status/all tests passed label Apr 11, 2019

jackysp approved these changes Apr 11, 2019

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Merge branch 'master' into feature/strict_compatibility

876342f

jackysp merged commit 28e6294 into pingcap:master Apr 11, 2019

zhexuany mentioned this pull request Apr 15, 2019

when I use in .NET (ef) variable 'tx_isolation' does not yet support value: SERIALIZABLE #8793

Closed

morgo mentioned this pull request Apr 18, 2019

LOCK TABLES does not warn/error when unsupported #10194

Closed

This was referenced Jun 25, 2019

get_lock() and release_lock() should produce errors #10929

Closed

*: add tidb_enable_noop_functions to default disable get_lock()/release_lock() #10987

Merged

wwar mentioned this pull request Jan 11, 2020

SQL_CALC_FOUND_ROWS behavior leads to data truncation #14448

Closed

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