Add GENERATED ALWAYS AS support for ALTER TABLE ALTER COLUMN

- Parse GENERATED ALWAYS AS SUSER_SID/SUSER_SNAME START/END
- Map to UserIdStart, UserIdEnd, UserNameStart, UserNameEnd values
- Fix AddMaskingFunction/DropMaskingFunction option names

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

ast/alter_table_alter_column_statement.go

@@ -13,6 +13,7 @@ type AlterTableAlterColumnStatement struct {
 	Encryption                  *ColumnEncryptionDefinition
 	MaskingFunction             ScalarExpression
 	Options                     []IndexOption
+	GeneratedAlways             string // UserIdStart, UserIdEnd, UserNameStart, UserNameEnd, etc.
 }
 
 func (a *AlterTableAlterColumnStatement) node()      {}

parser/marshal.go

@@ -976,6 +976,9 @@ func alterTableAlterColumnStatementToJSON(s *ast.AlterTableAlterColumnStatement)
 	if s.MaskingFunction != nil {
 		node["MaskingFunction"] = scalarExpressionToJSON(s.MaskingFunction)
 	}
+	if s.GeneratedAlways != "" {
+		node["GeneratedAlways"] = s.GeneratedAlways
+	}
 	if len(s.Options) > 0 {
 		opts := make([]jsonNode, len(s.Options))
 		for i, opt := range s.Options {

parser/parse_ddl.go

@@ -5073,7 +5073,7 @@ func (p *Parser) parseAlterTableAlterColumnStatement(tableName *ast.SchemaObject
 			stmt.AlterTableAlterColumnOption = "AddHidden"
 			p.nextToken()
 		} else if nextLit == "MASKED" {
-			stmt.AlterTableAlterColumnOption = "AddMasked"
+			stmt.AlterTableAlterColumnOption = "AddMaskingFunction"
 			stmt.IsMasked = true
 			p.nextToken()
 			// Parse optional WITH (FUNCTION = '...')
@@ -5135,7 +5135,7 @@ func (p *Parser) parseAlterTableAlterColumnStatement(tableName *ast.SchemaObject
 			stmt.AlterTableAlterColumnOption = "DropHidden"
 			p.nextToken()
 		} else if nextLit == "MASKED" {
-			stmt.AlterTableAlterColumnOption = "DropMasked"
+			stmt.AlterTableAlterColumnOption = "DropMaskingFunction"
 			p.nextToken()
 		} else if nextLit == "NOT" {
 			p.nextToken() // consume NOT
@@ -5247,6 +5247,35 @@ func (p *Parser) parseAlterTableAlterColumnStatement(tableName *ast.SchemaObject
 					p.nextToken() // consume )
 				}
 			}
+		} else if upperLit == "GENERATED" {
+			p.nextToken() // consume GENERATED
+			if strings.ToUpper(p.curTok.Literal) == "ALWAYS" {
+				p.nextToken() // consume ALWAYS
+			}
+			if strings.ToUpper(p.curTok.Literal) == "AS" {
+				p.nextToken() // consume AS
+			}
+			// Parse the generated type: SUSER_SID, SUSER_SNAME, etc.
+			genType := strings.ToUpper(p.curTok.Literal)
+			p.nextToken()
+			// Parse START or END
+			startEnd := strings.ToUpper(p.curTok.Literal)
+			p.nextToken()
+			// Map to expected values
+			switch genType {
+			case "SUSER_SID":
+				if startEnd == "START" {
+					stmt.GeneratedAlways = "UserIdStart"
+				} else if startEnd == "END" {
+					stmt.GeneratedAlways = "UserIdEnd"
+				}
+			case "SUSER_SNAME":
+				if startEnd == "START" {
+					stmt.GeneratedAlways = "UserNameStart"
+				} else if startEnd == "END" {
+					stmt.GeneratedAlways = "UserNameEnd"
+				}
+			}
 		} else {
 			break
 		}

parser/testdata/AlterTableAlterColumnStatementTests130/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/Baselines130_AlterTableAlterColumnStatementTests130/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}