SQL: Allow whitespaces in escape patterns (#47577)

Previously, we supported only the format `{fn <FUNCTION_NAME>()}`
but other DBs like MSSQL, DB2, MariaDB/MySQL alos allow whitespaces
between `{` and `fn`. Furhermore, also some applications - like PowerBI -
generate escape sequences with spaces: `select { fn name(params) } etc.`

Add support for white spaces between `{` and the escape pattern definition
like `fn`, `ts`, `d`, `guid` etc.

Closes: #47401

(cherry picked from commit 08a22d0)

Author: matriv

x-pack/plugin/sql/src/main/antlr/SqlBase.g4

@@ -201,7 +201,7 @@ pattern
 
 patternEscape
     : ESCAPE escape=string
-    | ESCAPE_ESC escape=string '}'
+    | ESCAPE_ESC escape=string ESC_END
     ;
 
 valueExpression
@@ -258,7 +258,7 @@ extractTemplate
 
 functionExpression
     : functionTemplate
-    | FUNCTION_ESC functionTemplate '}'
+    | FUNCTION_ESC functionTemplate ESC_END
     ;
 
 functionTemplate
@@ -461,15 +461,16 @@ YEAR: 'YEAR';
 YEARS: 'YEARS';
 
 // Escaped Sequence
-ESCAPE_ESC: '{ESCAPE';
-FUNCTION_ESC: '{FN';
-LIMIT_ESC:'{LIMIT';
-DATE_ESC: '{D';
-TIME_ESC: '{T';
-TIMESTAMP_ESC: '{TS';
+ESCAPE_ESC: ESC_START 'ESCAPE';
+FUNCTION_ESC: ESC_START 'FN';
+LIMIT_ESC: ESC_START 'LIMIT';
+DATE_ESC: ESC_START 'D';
+TIME_ESC: ESC_START 'T';
+TIMESTAMP_ESC: ESC_START 'TS';
 // mapped to string literal
-GUID_ESC: '{GUID';
+GUID_ESC: ESC_START 'GUID';
 
+ESC_START: '{' (WS)*;
 ESC_END: '}';
 
 // Operators

x-pack/plugin/sql/src/main/antlr/SqlBase.tokens

@@ -104,36 +104,37 @@ DATE_ESC=103
 TIME_ESC=104
 TIMESTAMP_ESC=105
 GUID_ESC=106
-ESC_END=107
-EQ=108
-NULLEQ=109
-NEQ=110
-LT=111
-LTE=112
-GT=113
-GTE=114
-PLUS=115
-MINUS=116
-ASTERISK=117
-SLASH=118
-PERCENT=119
-CAST_OP=120
-CONCAT=121
-DOT=122
-PARAM=123
-STRING=124
-INTEGER_VALUE=125
-DECIMAL_VALUE=126
-IDENTIFIER=127
-DIGIT_IDENTIFIER=128
-TABLE_IDENTIFIER=129
-QUOTED_IDENTIFIER=130
-BACKQUOTED_IDENTIFIER=131
-SIMPLE_COMMENT=132
-BRACKETED_COMMENT=133
-WS=134
-UNRECOGNIZED=135
-DELIMITER=136
+ESC_START=107
+ESC_END=108
+EQ=109
+NULLEQ=110
+NEQ=111
+LT=112
+LTE=113
+GT=114
+GTE=115
+PLUS=116
+MINUS=117
+ASTERISK=118
+SLASH=119
+PERCENT=120
+CAST_OP=121
+CONCAT=122
+DOT=123
+PARAM=124
+STRING=125
+INTEGER_VALUE=126
+DECIMAL_VALUE=127
+IDENTIFIER=128
+DIGIT_IDENTIFIER=129
+TABLE_IDENTIFIER=130
+QUOTED_IDENTIFIER=131
+BACKQUOTED_IDENTIFIER=132
+SIMPLE_COMMENT=133
+BRACKETED_COMMENT=134
+WS=135
+UNRECOGNIZED=136
+DELIMITER=137
 '('=1
 ')'=2
 ','=3
@@ -233,26 +234,19 @@ DELIMITER=136
 'WITH'=97
 'YEAR'=98
 'YEARS'=99
-'{ESCAPE'=100
-'{FN'=101
-'{LIMIT'=102
-'{D'=103
-'{T'=104
-'{TS'=105
-'{GUID'=106
-'}'=107
-'='=108
-'<=>'=109
-'<'=111
-'<='=112
-'>'=113
-'>='=114
-'+'=115
-'-'=116
-'*'=117
-'/'=118
-'%'=119
-'::'=120
-'||'=121
-'.'=122
-'?'=123
+'}'=108
+'='=109
+'<=>'=110
+'<'=112
+'<='=113
+'>'=114
+'>='=115
+'+'=116
+'-'=117
+'*'=118
+'/'=119
+'%'=120
+'::'=121
+'||'=122
+'.'=123
+'?'=124

x-pack/plugin/sql/src/main/antlr/SqlBaseLexer.tokens

@@ -104,35 +104,36 @@ DATE_ESC=103
 TIME_ESC=104
 TIMESTAMP_ESC=105
 GUID_ESC=106
-ESC_END=107
-EQ=108
-NULLEQ=109
-NEQ=110
-LT=111
-LTE=112
-GT=113
-GTE=114
-PLUS=115
-MINUS=116
-ASTERISK=117
-SLASH=118
-PERCENT=119
-CAST_OP=120
-CONCAT=121
-DOT=122
-PARAM=123
-STRING=124
-INTEGER_VALUE=125
-DECIMAL_VALUE=126
-IDENTIFIER=127
-DIGIT_IDENTIFIER=128
-TABLE_IDENTIFIER=129
-QUOTED_IDENTIFIER=130
-BACKQUOTED_IDENTIFIER=131
-SIMPLE_COMMENT=132
-BRACKETED_COMMENT=133
-WS=134
-UNRECOGNIZED=135
+ESC_START=107
+ESC_END=108
+EQ=109
+NULLEQ=110
+NEQ=111
+LT=112
+LTE=113
+GT=114
+GTE=115
+PLUS=116
+MINUS=117
+ASTERISK=118
+SLASH=119
+PERCENT=120
+CAST_OP=121
+CONCAT=122
+DOT=123
+PARAM=124
+STRING=125
+INTEGER_VALUE=126
+DECIMAL_VALUE=127
+IDENTIFIER=128
+DIGIT_IDENTIFIER=129
+TABLE_IDENTIFIER=130
+QUOTED_IDENTIFIER=131
+BACKQUOTED_IDENTIFIER=132
+SIMPLE_COMMENT=133
+BRACKETED_COMMENT=134
+WS=135
+UNRECOGNIZED=136
 '('=1
 ')'=2
 ','=3
@@ -232,26 +233,19 @@ UNRECOGNIZED=135
 'WITH'=97
 'YEAR'=98
 'YEARS'=99
-'{ESCAPE'=100
-'{FN'=101
-'{LIMIT'=102
-'{D'=103
-'{T'=104
-'{TS'=105
-'{GUID'=106
-'}'=107
-'='=108
-'<=>'=109
-'<'=111
-'<='=112
-'>'=113
-'>='=114
-'+'=115
-'-'=116
-'*'=117
-'/'=118
-'%'=119
-'::'=120
-'||'=121
-'.'=122
-'?'=123
+'}'=108
+'='=109
+'<=>'=110
+'<'=112
+'<='=113
+'>'=114
+'>='=115
+'+'=116
+'-'=117
+'*'=118
+'/'=119
+'%'=120
+'::'=121
+'||'=122
+'.'=123
+'?'=124