Add ALTER COLUMN support for ALTER FULLTEXT INDEX statement

- Added AlterColumnAlterFullTextIndexAction AST type
- Added parsing for ALTER COLUMN clause in ALTER FULLTEXT INDEX
- Added JSON marshaling for the new type

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

Author: kyleconroy

ast/alter_simple_statements.go

@@ -295,6 +295,15 @@ type DropAlterFullTextIndexAction struct {
 func (*DropAlterFullTextIndexAction) node()                     {}
 func (*DropAlterFullTextIndexAction) alterFullTextIndexAction() {}
 
+// AlterColumnAlterFullTextIndexAction represents an ALTER COLUMN action for fulltext index
+type AlterColumnAlterFullTextIndexAction struct {
+	Column           *FullTextIndexColumn `json:"Column,omitempty"`
+	WithNoPopulation bool                 `json:"WithNoPopulation"`
+}
+
+func (*AlterColumnAlterFullTextIndexAction) node()                     {}
+func (*AlterColumnAlterFullTextIndexAction) alterFullTextIndexAction() {}
+
 // FullTextIndexColumn represents a column in a fulltext index
 type FullTextIndexColumn struct {
 	Name                 *Identifier              `json:"Name,omitempty"`

parser/marshal.go

@@ -17658,6 +17658,15 @@ func alterFullTextIndexActionToJSON(a ast.AlterFullTextIndexActionOption) jsonNo
 			node["StopListOption"] = stopListFullTextIndexOptionToJSON(action.StopListOption)
 		}
 		return node
+	case *ast.AlterColumnAlterFullTextIndexAction:
+		node := jsonNode{
+			"$type":            "AlterColumnAlterFullTextIndexAction",
+			"WithNoPopulation": action.WithNoPopulation,
+		}
+		if action.Column != nil {
+			node["Column"] = fullTextIndexColumnToJSON(action.Column)
+		}
+		return node
 	}
 	return nil
 }

parser/parse_ddl.go

@@ -8737,12 +8737,59 @@ func (p *Parser) tryParseAlterFullTextIndexAction() ast.AlterFullTextIndexAction
 	case "DROP":
 		action, _ := p.parseDropAlterFullTextIndexAction()
 		return action
+	case "ALTER":
+		action, _ := p.parseAlterColumnAlterFullTextIndexAction()
+		return action
 	}
 
 	// No action found
 	return nil
 }
 
+func (p *Parser) parseAlterColumnAlterFullTextIndexAction() (*ast.AlterColumnAlterFullTextIndexAction, error) {
+	p.nextToken() // consume ALTER
+
+	if strings.ToUpper(p.curTok.Literal) != "COLUMN" {
+		return nil, fmt.Errorf("expected COLUMN after ALTER, got %s", p.curTok.Literal)
+	}
+	p.nextToken() // consume COLUMN
+
+	action := &ast.AlterColumnAlterFullTextIndexAction{
+		Column: &ast.FullTextIndexColumn{
+			Name: p.parseIdentifier(),
+		},
+	}
+
+	// Parse ADD or DROP STATISTICAL_SEMANTICS
+	if strings.ToUpper(p.curTok.Literal) == "ADD" {
+		p.nextToken() // consume ADD
+		if strings.ToUpper(p.curTok.Literal) == "STATISTICAL_SEMANTICS" {
+			p.nextToken() // consume STATISTICAL_SEMANTICS
+			action.Column.StatisticalSemantics = true
+		}
+	} else if strings.ToUpper(p.curTok.Literal) == "DROP" {
+		p.nextToken() // consume DROP
+		if strings.ToUpper(p.curTok.Literal) == "STATISTICAL_SEMANTICS" {
+			p.nextToken() // consume STATISTICAL_SEMANTICS
+			action.Column.StatisticalSemantics = false
+		}
+	}
+
+	// Check for WITH NO POPULATION
+	if p.curTok.Type == TokenWith {
+		p.nextToken() // consume WITH
+		if strings.ToUpper(p.curTok.Literal) == "NO" {
+			p.nextToken() // consume NO
+			if strings.ToUpper(p.curTok.Literal) == "POPULATION" {
+				p.nextToken() // consume POPULATION
+				action.WithNoPopulation = true
+			}
+		}
+	}
+
+	return action, nil
+}
+
 func (p *Parser) parseAddAlterFullTextIndexAction() (*ast.AddAlterFullTextIndexAction, error) {
 	p.nextToken() // consume ADD