feat(parser): Snowflake MINUS fix, CLUSTER BY, COPY GRANTS, CTAS (#483) (#504)

Co-authored-by: Ajit Pratap Singh <ajitpratapsingh@Ajits-Mac-mini-2655.local>

Author: ajitpratap0

pkg/sql/parser/ddl.go

@@ -179,6 +179,29 @@ func (p *Parser) parseCreateTable(temporary bool) (*ast.CreateTableStatement, er
 	}
 	stmt.Name = createTableName
 
+	// Snowflake: COPY GRANTS modifier before the column list or AS SELECT.
+	// Consumed but not modeled on the AST.
+	if strings.EqualFold(p.currentToken.Token.Value, "COPY") &&
+		strings.EqualFold(p.peekToken().Token.Value, "GRANTS") {
+		p.advance() // COPY
+		p.advance() // GRANTS
+	}
+
+	// CREATE TABLE ... AS SELECT — no column list, just a query.
+	if p.isType(models.TokenTypeAs) {
+		p.advance() // AS
+		if p.isType(models.TokenTypeSelect) || p.isType(models.TokenTypeWith) {
+			p.advance() // SELECT / WITH
+			query, err := p.parseSelectWithSetOperations()
+			if err != nil {
+				return nil, err
+			}
+			_ = query // CTAS query not modeled on CreateTableStatement yet
+			return stmt, nil
+		}
+		return nil, p.expectedError("SELECT after AS")
+	}
+
 	// Expect opening parenthesis for column definitions
 	if !p.isType(models.TokenTypeLParen) {
 		return nil, p.expectedError("(")
@@ -379,6 +402,19 @@ func (p *Parser) parseCreateTable(temporary bool) (*ast.CreateTableStatement, er
 		break
 	}
 
+	// Snowflake: CLUSTER BY (expr, ...) — defines the clustering key.
+	if strings.EqualFold(p.currentToken.Token.Value, "CLUSTER") {
+		p.advance() // CLUSTER
+		if p.isType(models.TokenTypeBy) {
+			p.advance() // BY
+		}
+		if p.isType(models.TokenTypeLParen) {
+			if err := p.skipClickHouseClauseExpr(); err != nil {
+				return nil, err
+			}
+		}
+	}
+
 	// SQLite: optional WITHOUT ROWID clause
 	if p.isTokenMatch("WITHOUT") {
 		p.advance() // Consume WITHOUT

pkg/sql/parser/parser.go

@@ -1080,9 +1080,14 @@ func (p *Parser) isNonReservedKeyword() bool {
 	return false
 }
 
-// canBeAlias checks if current token can be used as an alias
-// Aliases can be IDENT, double-quoted identifiers, or certain non-reserved keywords
+// canBeAlias checks if current token can be used as an alias.
+// Aliases can be IDENT, double-quoted identifiers, or certain non-reserved keywords,
+// but NOT contextual clause keywords that would be consumed as aliases by mistake
+// (e.g. MINUS in Snowflake/Oracle, QUALIFY in Snowflake/BigQuery).
 func (p *Parser) canBeAlias() bool {
+	if p.isMinusSetOp() || p.isQualifyKeyword() {
+		return false
+	}
 	return p.isIdentifier() || p.isNonReservedKeyword()
 }
 

pkg/sql/parser/select_clauses.go

@@ -61,7 +61,8 @@ func (p *Parser) parseFromClause() (tableName string, tables []ast.TableReferenc
 		if !p.isType(models.TokenTypeEOF) &&
 			!p.isType(models.TokenTypeSemicolon) &&
 			!p.isType(models.TokenTypeRParen) &&
-			!p.isAnyType(models.TokenTypeUnion, models.TokenTypeExcept, models.TokenTypeIntersect) {
+			!p.isAnyType(models.TokenTypeUnion, models.TokenTypeExcept, models.TokenTypeIntersect) &&
+			!p.isMinusSetOp() {
 			return "", nil, nil, p.expectedError("FROM, semicolon, or end of statement")
 		}
 		return "", nil, nil, nil