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| Original file line number | Diff line number | Diff line change |
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| // Copyright 2020 PingCAP, Inc. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package driver | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "regexp" | ||
|
|
||
| "github.com/pingcap/parser" | ||
| ) | ||
|
|
||
| // To add new features that needs to be downgrade-compatible, | ||
| // 1. Define a featureID below and make sure it is unique. | ||
| // For example, `const FeatureIDMyFea = "my_fea"`. | ||
| // 2. Register the new featureID in init(). | ||
| // Only the registered parser can parse the comment annotated with `my_fea`. | ||
| // Now, the parser treats `/*T![my_fea] what_ever */` and `what_ever` equivalent. | ||
| // In other word, the parser in old-version TiDB will ignores these comments. | ||
| // 3. [optional] Add a pattern into FeatureIDPatterns. | ||
| // This is only required if the new feature is contained in DDL, | ||
| // and we want to comment out this part of SQL in binlog. | ||
| func init() { | ||
| parser.SpecialCommentsController.Register(string(FeatureIDAutoRandom)) | ||
| } | ||
|
|
||
| // SpecialCommentVersionPrefix is the prefix of TiDB executable comments. | ||
| const SpecialCommentVersionPrefix = `/*T!` | ||
|
|
||
| // BuildSpecialCommentPrefix returns the prefix of `featureID` special comment. | ||
| func BuildSpecialCommentPrefix(featureID featureID) string { | ||
| return fmt.Sprintf("%s[%s]", SpecialCommentVersionPrefix, featureID) | ||
| } | ||
|
|
||
| type featureID string | ||
|
|
||
| const ( | ||
| // FeatureIDAutoRandom is the `auto_random` feature. | ||
| FeatureIDAutoRandom featureID = "auto_rand" | ||
| ) | ||
|
|
||
| // FeatureIDPatterns is used to record special comments patterns. | ||
| var FeatureIDPatterns = map[featureID]*regexp.Regexp{ | ||
| FeatureIDAutoRandom: regexp.MustCompile(`(?i)AUTO_RANDOM\s*(\(\s*\d+\s*\))?\s*`), | ||
| } |