feat: match empty column when in entityCollecting context

src/grammar/flink/FlinkSqlParser.g4

@@ -184,15 +184,24 @@ columnNameCreate
     | expression
     ;
 
+emptyColumn
+    :
+    ;
+
 columnName
-    : uid
-    | {this.shouldMatchEmpty()}?
+    : uidAllowEmpty
+    | {this.shouldMatchEmpty()}? emptyColumn
     ;
 
 columnNamePath
     : uid
     ;
 
+columnNamePathAllowEmpty
+    : uidAllowEmpty
+    | {this.shouldMatchEmpty()}? emptyColumn
+    ;
+
 columnNameList
     : LR_BRACKET columnName (COMMA columnName)* RR_BRACKET
     ;
@@ -614,12 +623,12 @@ columnDescriptor
     ;
 
 joinCondition
-    : KW_ON booleanExpression
+    : KW_ON (booleanExpression | columnNamePathAllowEmpty (EQUAL_SYMBOL columnNamePathAllowEmpty)?)
     | KW_USING columnNameList
     ;
 
 whereClause
-    : KW_WHERE booleanExpression
+    : KW_WHERE (booleanExpression | columnNamePathAllowEmpty)
     ;
 
 groupByClause
@@ -983,6 +992,11 @@ uid
     : identifier (DOT identifier)*
     ;
 
+uidAllowEmpty
+    : identifier (DOT identifier)*
+    | {this.shouldMatchEmpty()}? identifier DOT emptyColumn
+    ;
+
 withOption
     : KW_WITH tablePropertyList
     ;

src/grammar/hive/HiveSqlParser.g4

@@ -754,14 +754,19 @@ columnNameList
     ;
 
 columnName
-    : poolPath
-    | {this.shouldMatchEmpty()}?
+    : poolPathAllowEmpty
+    | {this.shouldMatchEmpty()}? emptyColumn
     ;
 
 columnNamePath
     : poolPath
     ;
 
+columnNamePathAllowEmpty
+    : poolPathAllowEmpty
+    | {this.shouldMatchEmpty()}? emptyColumn
+    ;
+
 columnNameCreate
     : id_
     ;
@@ -1346,7 +1351,10 @@ atomjoinSource
 
 joinSource
     : atomjoinSource (
-        joinToken joinSourcePart (KW_ON expression | KW_USING columnParenthesesList)?
+        joinToken joinSourcePart (
+            KW_ON (expression | columnNamePathAllowEmpty (EQUAL columnNamePathAllowEmpty)?)
+            | KW_USING columnParenthesesList
+        )?
     )*
     ;
 
@@ -1469,7 +1477,7 @@ Rules for parsing whereClause
  where a=b and ...
 */
 whereClause
-    : KW_WHERE expression
+    : KW_WHERE (expression | columnNamePathAllowEmpty)
     ;
 
 /**
@@ -1600,7 +1608,7 @@ groupingSetExpression
     ;
 
 havingClause
-    : KW_HAVING expression
+    : KW_HAVING (expression | columnNamePathAllowEmpty)
     ;
 
 qualifyClause
@@ -2425,10 +2433,19 @@ decimal
     | KW_NUMERIC
     ;
 
+emptyColumn
+    :
+    ;
+
 poolPath
     : id_ (DOT id_)*
     ;
 
+poolPathAllowEmpty
+    : id_ (DOT id_)*
+    | {this.shouldMatchEmpty()}? id_ (DOT emptyColumn)*
+    ;
+
 triggerAtomExpression
     : id_ GREATERTHAN (Number | StringLiteral)
     ;

src/grammar/impala/ImpalaSqlParser.g4

@@ -558,15 +558,24 @@ functionNamePath
     | qualifiedName
     ;
 
+emptyColumn
+    :
+    ;
+
 columnNamePath
-    : qualifiedName
-    | {this.shouldMatchEmpty()}?
+    : {this.shouldMatchEmpty()}? emptyColumn
+    | qualifiedNameAllowEmpty
     ;
 
 columnName
     : qualifiedName
     ;
 
+columnNameAllowEmpty
+    : {this.shouldMatchEmpty()}? emptyColumn
+    | qualifiedNameAllowEmpty
+    ;
+
 tableOrViewPath
     : tableNamePath
     | viewNamePath
@@ -781,11 +790,11 @@ selectList
     ;
 
 whereClause
-    : KW_WHERE where=booleanExpression
+    : KW_WHERE (where=booleanExpression | columnNameAllowEmpty)
     ;
 
 havingClause
-    : KW_HAVING having=booleanExpression
+    : KW_HAVING (having=booleanExpression | columnNameAllowEmpty)
     ;
 
 groupBy
@@ -854,7 +863,7 @@ joinType
     ;
 
 joinCriteria
-    : KW_ON booleanExpression
+    : KW_ON (booleanExpression | columnNameAllowEmpty)
     | KW_USING LPAREN identifier (COMMA identifier)* RPAREN
     ;
 
@@ -1149,6 +1158,11 @@ qualifiedName
     : identifier (DOT identifier)*
     ;
 
+qualifiedNameAllowEmpty
+    : {this.shouldMatchEmpty()}? (identifier DOT emptyColumn | emptyColumn)
+    | identifier (DOT identifier)*
+    ;
+
 principal
     : KW_ROLE identifier  # rolePrincipal
     | KW_USER identifier  # userPrincipal

src/grammar/mysql/MySqlParser.g4

@@ -1122,7 +1122,7 @@ joinPart
     ;
 
 joinSpec
-    : (KW_ON expression)
+    : (KW_ON (expression | columnNamePathAllowEmpty))
     | KW_USING '(' columnNames ')'
     ;
 
@@ -1249,7 +1249,7 @@ selectLinesInto
     ;
 
 fromClause
-    : (KW_FROM tableSources)? (KW_WHERE whereExpr=expression)?
+    : (KW_FROM tableSources)? (KW_WHERE (whereExpr=expression | columnNamePathAllowEmpty))?
     ;
 
 groupByClause
@@ -2419,10 +2419,24 @@ columnNames
     : columnName (',' columnName)*
     ;
 
+emptyColumn
+    :
+    ;
+
 columnName
+    : uid (dottedIdAllowEmpty dottedIdAllowEmpty?)?
+    | .? dottedId dottedId?
+    | {this.shouldMatchEmpty()}? emptyColumn
+    ;
+
+columnNamePath
     : uid (dottedId dottedId?)?
     | .? dottedId dottedId?
-    | {this.shouldMatchEmpty()}?
+    ;
+
+columnNamePathAllowEmpty
+    : {this.shouldMatchEmpty()}? emptyColumn
+    | uid (dottedIdAllowEmpty dottedIdAllowEmpty?)?
     ;
 
 tableSpaceNameCreate
@@ -2560,6 +2574,12 @@ dottedId
     | '.' uid
     ;
 
+dottedIdAllowEmpty
+    : DOT ID
+    | '.' uid
+    | {this.shouldMatchEmpty()}? DOT emptyColumn
+    ;
+
 decimalLiteral
     : DECIMAL_LITERAL
     | ZERO_DECIMAL
@@ -2998,7 +3018,7 @@ expressionAtom
     | left=expressionAtom jsonOperator right=expressionAtom # jsonExpressionAtom
     | left=expressionAtom bitOperator right=expressionAtom  # bitExpressionAtom
     | left=expressionAtom mathOperator right=expressionAtom # mathExpressionAtom
-    | columnName                                            # columnNameExpressionAtom
+    | columnNamePath                                        # columnNameExpressionAtom
     ;
 
 unaryOperator

src/grammar/postgresql/PostgreSqlParser.g4

@@ -2722,13 +2722,18 @@ procedureNameCreate
     | colId indirection
     ;
 
+emptyColumn
+    :
+    ;
+
 columnName
     : colId optIndirection
-    | {this.shouldMatchEmpty()}?
+    | {this.shouldMatchEmpty()}? (colId DOT emptyColumn | emptyColumn)
     ;
 
 columnNamePath
     : colId optIndirection
+    | {this.shouldMatchEmpty()}? (colId DOT emptyColumn | emptyColumn)
     ;
 
 columnNameCreate

src/grammar/spark/SparkSqlParser.g4

@@ -413,15 +413,24 @@ viewName
     : viewIdentifier
     ;
 
+emptyColumn
+    :
+    ;
+
 columnName
-    : multipartIdentifier
-    | {this.shouldMatchEmpty()}?
+    : multipartIdentifierAllowEmpty
+    | {this.shouldMatchEmpty()}? emptyColumn
     ;
 
 columnNamePath
     : multipartIdentifier
     ;
 
+columnNamePathAllowEmpty
+    : multipartIdentifierAllowEmpty
+    | {this.shouldMatchEmpty()}? emptyColumn
+    ;
+
 columnNameSeq
     : columnName (COMMA columnName)*
     ;
@@ -680,7 +689,7 @@ joinType
     ;
 
 joinCriteria
-    : KW_ON booleanExpression
+    : KW_ON (booleanExpression | columnNamePathAllowEmpty (EQ columnNamePathAllowEmpty)?)
     | KW_USING identifierList
     ;
 
@@ -804,6 +813,11 @@ multipartIdentifier
     : parts+=errorCapturingIdentifier (DOT parts+=errorCapturingIdentifier)*
     ;
 
+multipartIdentifierAllowEmpty
+    : multipartIdentifier
+    | {this.shouldMatchEmpty()}? multipartIdentifier DOT emptyColumn
+    ;
+
 multipartIdentifierPropertyList
     : multipartIdentifierProperty (COMMA multipartIdentifierProperty)*
     ;