SQL: Allow whitespaces in escape patterns

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

Author: matriv

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

@@ -217,7 +217,7 @@ pattern
 
 patternEscape
     : ESCAPE escape=string
-    | ESCAPE_ESC escape=string '}'
+    | ESCAPE_ESC escape=string ESC_END
     ;
 
 valueExpression
@@ -274,7 +274,7 @@ extractTemplate
 
 functionExpression
     : functionTemplate
-    | FUNCTION_ESC functionTemplate '}'
+    | FUNCTION_ESC functionTemplate ESC_END
     ;
 
 functionTemplate
@@ -480,15 +480,16 @@ 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

@@ -106,36 +106,37 @@ DATE_ESC=105
 TIME_ESC=106
 TIMESTAMP_ESC=107
 GUID_ESC=108
-ESC_END=109
-EQ=110
-NULLEQ=111
-NEQ=112
-LT=113
-LTE=114
-GT=115
-GTE=116
-PLUS=117
-MINUS=118
-ASTERISK=119
-SLASH=120
-PERCENT=121
-CAST_OP=122
-CONCAT=123
-DOT=124
-PARAM=125
-STRING=126
-INTEGER_VALUE=127
-DECIMAL_VALUE=128
-IDENTIFIER=129
-DIGIT_IDENTIFIER=130
-TABLE_IDENTIFIER=131
-QUOTED_IDENTIFIER=132
-BACKQUOTED_IDENTIFIER=133
-SIMPLE_COMMENT=134
-BRACKETED_COMMENT=135
-WS=136
-UNRECOGNIZED=137
-DELIMITER=138
+ESC_START=109
+ESC_END=110
+EQ=111
+NULLEQ=112
+NEQ=113
+LT=114
+LTE=115
+GT=116
+GTE=117
+PLUS=118
+MINUS=119
+ASTERISK=120
+SLASH=121
+PERCENT=122
+CAST_OP=123
+CONCAT=124
+DOT=125
+PARAM=126
+STRING=127
+INTEGER_VALUE=128
+DECIMAL_VALUE=129
+IDENTIFIER=130
+DIGIT_IDENTIFIER=131
+TABLE_IDENTIFIER=132
+QUOTED_IDENTIFIER=133
+BACKQUOTED_IDENTIFIER=134
+SIMPLE_COMMENT=135
+BRACKETED_COMMENT=136
+WS=137
+UNRECOGNIZED=138
+DELIMITER=139
 '('=1
 ')'=2
 ','=3
@@ -237,26 +238,19 @@ DELIMITER=138
 'WITH'=99
 'YEAR'=100
 'YEARS'=101
-'{ESCAPE'=102
-'{FN'=103
-'{LIMIT'=104
-'{D'=105
-'{T'=106
-'{TS'=107
-'{GUID'=108
-'}'=109
-'='=110
-'<=>'=111
-'<'=113
-'<='=114
-'>'=115
-'>='=116
-'+'=117
-'-'=118
-'*'=119
-'/'=120
-'%'=121
-'::'=122
-'||'=123
-'.'=124
-'?'=125
+'}'=110
+'='=111
+'<=>'=112
+'<'=114
+'<='=115
+'>'=116
+'>='=117
+'+'=118
+'-'=119
+'*'=120
+'/'=121
+'%'=122
+'::'=123
+'||'=124
+'.'=125
+'?'=126

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

@@ -106,35 +106,36 @@ DATE_ESC=105
 TIME_ESC=106
 TIMESTAMP_ESC=107
 GUID_ESC=108
-ESC_END=109
-EQ=110
-NULLEQ=111
-NEQ=112
-LT=113
-LTE=114
-GT=115
-GTE=116
-PLUS=117
-MINUS=118
-ASTERISK=119
-SLASH=120
-PERCENT=121
-CAST_OP=122
-CONCAT=123
-DOT=124
-PARAM=125
-STRING=126
-INTEGER_VALUE=127
-DECIMAL_VALUE=128
-IDENTIFIER=129
-DIGIT_IDENTIFIER=130
-TABLE_IDENTIFIER=131
-QUOTED_IDENTIFIER=132
-BACKQUOTED_IDENTIFIER=133
-SIMPLE_COMMENT=134
-BRACKETED_COMMENT=135
-WS=136
-UNRECOGNIZED=137
+ESC_START=109
+ESC_END=110
+EQ=111
+NULLEQ=112
+NEQ=113
+LT=114
+LTE=115
+GT=116
+GTE=117
+PLUS=118
+MINUS=119
+ASTERISK=120
+SLASH=121
+PERCENT=122
+CAST_OP=123
+CONCAT=124
+DOT=125
+PARAM=126
+STRING=127
+INTEGER_VALUE=128
+DECIMAL_VALUE=129
+IDENTIFIER=130
+DIGIT_IDENTIFIER=131
+TABLE_IDENTIFIER=132
+QUOTED_IDENTIFIER=133
+BACKQUOTED_IDENTIFIER=134
+SIMPLE_COMMENT=135
+BRACKETED_COMMENT=136
+WS=137
+UNRECOGNIZED=138
 '('=1
 ')'=2
 ','=3
@@ -236,26 +237,19 @@ UNRECOGNIZED=137
 'WITH'=99
 'YEAR'=100
 'YEARS'=101
-'{ESCAPE'=102
-'{FN'=103
-'{LIMIT'=104
-'{D'=105
-'{T'=106
-'{TS'=107
-'{GUID'=108
-'}'=109
-'='=110
-'<=>'=111
-'<'=113
-'<='=114
-'>'=115
-'>='=116
-'+'=117
-'-'=118
-'*'=119
-'/'=120
-'%'=121
-'::'=122
-'||'=123
-'.'=124
-'?'=125
+'}'=110
+'='=111
+'<=>'=112
+'<'=114
+'<='=115
+'>'=116
+'>='=117
+'+'=118
+'-'=119
+'*'=120
+'/'=121
+'%'=122
+'::'=123
+'||'=124
+'.'=125
+'?'=126