From e47fb502b27a0a8187fc14bc079b0501cee0a68b Mon Sep 17 00:00:00 2001
From: sduzh <zhuming9011@qq.com>
Date: Thu, 10 Dec 2020 21:34:06 +0800
Subject: [PATCH] [Compatibility] Support embedded quota in string literal
 (#5045)

```
mysql> select 'I''m a student';
+-----------------+
| 'I'm a student' |
+-----------------+
| I'm a student   |
+-----------------+

mysql> select "I""m a student";
+-----------------+
| 'I"m a student' |
+-----------------+
| I"m a student   |
+-----------------+

mysql> select 'I""m a student';
+------------------+
| 'I""m a student' |
+------------------+
| I""m a student   |
+------------------+

mysql> select "I''m a student";
+------------------+
| 'I''m a student' |
+------------------+
| I''m a student   |
+------------------+
```
---
 fe/fe-core/src/main/jflex/sql_scanner.flex | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fe/fe-core/src/main/jflex/sql_scanner.flex b/fe/fe-core/src/main/jflex/sql_scanner.flex
index bbd0435ec1..e50be25c85 100644
--- a/fe/fe-core/src/main/jflex/sql_scanner.flex
+++ b/fe/fe-core/src/main/jflex/sql_scanner.flex
@@ -506,8 +506,8 @@ IdentifierOrKwContents = [:digit:]*[:jletter:][:jletterdigit:]* | "&&" | "||"
 IdentifierOrKw = \`{IdentifierOrKwContents}\` | {IdentifierOrKwContents}
 IntegerLiteral = [:digit:][:digit:]*
 QuotedIdentifier = \`(\`\`|[^\`])*\`
-SingleQuoteStringLiteral = \'(\\.|[^\\\'])*\'
-DoubleQuoteStringLiteral = \"(\\.|[^\\\"])*\"
+SingleQuoteStringLiteral = \'(\\.|[^\\\']|\'\')*\'
+DoubleQuoteStringLiteral = \"(\\.|[^\\\"]|\"\")*\"
 
 FLit1 = [0-9]+ \. [0-9]*
 FLit2 = \. [0-9]+
@@ -595,12 +595,12 @@ EndOfLineComment = "--" !({HintContent}|{ContainsLineTerminator}) {LineTerminato
 
 {SingleQuoteStringLiteral} {
   return newToken(SqlParserSymbols.STRING_LITERAL,
-                  escapeBackSlash(yytext().substring(1, yytext().length()-1)));
+      escapeBackSlash(yytext().substring(1, yytext().length()-1)).replaceAll("''", "'"));
 }
 
 {DoubleQuoteStringLiteral} {
   return newToken(SqlParserSymbols.STRING_LITERAL,
-                  escapeBackSlash(yytext().substring(1, yytext().length()-1)));
+      escapeBackSlash(yytext().substring(1, yytext().length()-1)).replaceAll("\"\"", "\""));
 }
 
 {CommentedHintBegin} {