[mysql/Oracle] Grammar is ambiguous.

[kaby76]

I've ported the sql/mysql/Oracle grammar to CSharp. I found that the grammar is ambiguous.

$ dotnet trparse ../examples/expressions.sql --ambig | dotnet trtree -a
CSharp 0 ../examples/expressions.sql success 0.139722
(query (simpleStatement (selectStatement (queryExpression (queryExpressionBody (queryPrimary (querySpecification (SELECT_SYMBOL "select") (selectItemList (selectItem (expr (boolPri (predicate (bitExpr (bitExpr (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "1"))))))) (PLUS_OPERATOR "+") (bitExpr (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "2"))))))) (MULT_OPERATOR "*") (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "3"))))))))) (MINUS_OPERATOR "-") (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "4"))))))))))))))))))) (SEMICOLON_SYMBOL ";"))
(query (simpleStatement (selectStatement (queryExpression (queryExpressionBody (queryPrimary (querySpecification (SELECT_SYMBOL "select") (selectItemList (selectItem (expr (boolPri (predicate (bitExpr (bitExpr (bitExpr (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "1"))))))) (PLUS_OPERATOR "+") (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "2")))))))) (MULT_OPERATOR "*") (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "3")))))))) (MINUS_OPERATOR "-") (bitExpr (simpleExpr (literalOrNull (literal (numLiteral (int64Literal (INT_NUMBER "4"))))))))))))))))))) (SEMICOLON_SYMBOL ";"))

(The main reason I did the CSharp port was to check for ambiguities in this grammar. All tools in Trash are in C#.)

Another example comes from the MySQL Reference manual https://dev.mysql.com/doc/refman/8.4/en/select.html.

$ dotnet trparse --ambig -i "SELECT CONCAT(last_name,', ',first_name) AS full_name FROM mytable ORDER BY full_name;" | dotnet trtree
-a
CSharp 0 string success 0.2263846
(queries (query (simpleStatement (selectStatement (queryExpression (queryExpressionBody (queryPrimary (querySpecification (SELECT_SYMBOL "SELECT") (selectItemList (selectItem (expr (boolPri (predicate (bitExpr (simpleExpr (functionCall (pureIdentifier (IDENTIFIER "CONCAT")) (OPEN_PAR_SYMBOL "(") (udfExprList (udfExpr (expr (boolPri (predicate (bitExpr (simpleExpr (columnRef (fieldIdentifier (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "last_name")))))))))))) (COMMA_SYMBOL ",") (udfExpr (expr (boolPri (predicate (bitExpr (simpleExpr (literalOrNull (literal (textLiteral (textStringLiteral (SINGLE_QUOTED_TEXT "', '"))))))))))) (COMMA_SYMBOL ",") (udfExpr (expr (boolPri (predicate (bitExpr (simpleExpr (columnRef (fieldIdentifier (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "first_name"))))))))))))) (CLOSE_PAR_SYMBOL ")"))))))) (selectAlias (AS_SYMBOL "AS") (identifier (pureIdentifier (IDENTIFIER "full_name")))))) (fromClause (FROM_SYMBOL "FROM") (tableReferenceList (tableReference (tableFactor (singleTable (tableRef (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "mytable"))))))))))))) (orderClause (ORDER_SYMBOL "ORDER") (BY_SYMBOL "BY") (orderList (orderExpression (expr (boolPri (predicate (bitExpr (simpleExpr (columnRef (fieldIdentifier (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "full_name"))))))))))))))))) (SEMICOLON_SYMBOL ";")) (EOF ""))
(queries (query (simpleStatement (selectStatement (queryExpression (queryExpressionBody (queryPrimary (querySpecification (SELECT_SYMBOL "SELECT") (selectItemList (selectItem (expr (boolPri (predicate (bitExpr (simpleExpr (functionCall (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "CONCAT")))) (OPEN_PAR_SYMBOL "(") (exprList (expr (boolPri (predicate (bitExpr (simpleExpr (columnRef (fieldIdentifier (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "last_name"))))))))))) (COMMA_SYMBOL ",") (expr (boolPri (predicate (bitExpr (simpleExpr (literalOrNull (literal (textLiteral (textStringLiteral (SINGLE_QUOTED_TEXT "', '")))))))))) (COMMA_SYMBOL ",") (expr (boolPri (predicate (bitExpr (simpleExpr (columnRef (fieldIdentifier (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "first_name")))))))))))) (CLOSE_PAR_SYMBOL ")"))))))) (selectAlias (AS_SYMBOL "AS") (identifier (pureIdentifier (IDENTIFIER "full_name")))))) (fromClause (FROM_SYMBOL "FROM") (tableReferenceList (tableReference (tableFactor (singleTable (tableRef (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "mytable"))))))))))))) (orderClause (ORDER_SYMBOL "ORDER") (BY_SYMBOL "BY") (orderList (orderExpression (expr (boolPri (predicate (bitExpr (simpleExpr (columnRef (fieldIdentifier (qualifiedIdentifier (identifier (pureIdentifier (IDENTIFIER "full_name"))))))))))))))))) (SEMICOLON_SYMBOL ";")) (EOF ""))

Ambiguity is a problem because it causes performance issues for Antlr4.