Add AUTOMATIC_TUNING database option parsing support

- Add AutomaticTuningDatabaseOption and sub-option AST types
- Parse AUTOMATIC_TUNING = INHERIT|CUSTOM|AUTO
- Parse AUTOMATIC_TUNING (CREATE_INDEX = ON, DROP_INDEX = OFF, ...)
- Add JSON marshaling for automatic tuning options

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

Author: kyleconroy

ast/alter_database_set_statement.go

@@ -115,6 +115,58 @@ func (l *LiteralDatabaseOption) node()                 {}
 func (l *LiteralDatabaseOption) databaseOption()       {}
 func (l *LiteralDatabaseOption) createDatabaseOption() {}
 
+// AutomaticTuningDatabaseOption represents AUTOMATIC_TUNING option
+type AutomaticTuningDatabaseOption struct {
+	OptionKind            string                   // "AutomaticTuning"
+	AutomaticTuningState  string                   // "Inherit", "Custom", "Auto", "NotSet"
+	Options               []AutomaticTuningOption  // Sub-options like CREATE_INDEX, DROP_INDEX, etc.
+}
+
+func (a *AutomaticTuningDatabaseOption) node()           {}
+func (a *AutomaticTuningDatabaseOption) databaseOption() {}
+
+// AutomaticTuningOption is an interface for automatic tuning sub-options
+type AutomaticTuningOption interface {
+	Node
+	automaticTuningOption()
+}
+
+// AutomaticTuningCreateIndexOption represents CREATE_INDEX option
+type AutomaticTuningCreateIndexOption struct {
+	OptionKind string // "Create_Index"
+	Value      string // "On", "Off", "Default"
+}
+
+func (a *AutomaticTuningCreateIndexOption) node()                  {}
+func (a *AutomaticTuningCreateIndexOption) automaticTuningOption() {}
+
+// AutomaticTuningDropIndexOption represents DROP_INDEX option
+type AutomaticTuningDropIndexOption struct {
+	OptionKind string // "Drop_Index"
+	Value      string // "On", "Off", "Default"
+}
+
+func (a *AutomaticTuningDropIndexOption) node()                  {}
+func (a *AutomaticTuningDropIndexOption) automaticTuningOption() {}
+
+// AutomaticTuningForceLastGoodPlanOption represents FORCE_LAST_GOOD_PLAN option
+type AutomaticTuningForceLastGoodPlanOption struct {
+	OptionKind string // "Force_Last_Good_Plan"
+	Value      string // "On", "Off", "Default"
+}
+
+func (a *AutomaticTuningForceLastGoodPlanOption) node()                  {}
+func (a *AutomaticTuningForceLastGoodPlanOption) automaticTuningOption() {}
+
+// AutomaticTuningMaintainIndexOption represents MAINTAIN_INDEX option
+type AutomaticTuningMaintainIndexOption struct {
+	OptionKind string // "Maintain_Index"
+	Value      string // "On", "Off", "Default"
+}
+
+func (a *AutomaticTuningMaintainIndexOption) node()                  {}
+func (a *AutomaticTuningMaintainIndexOption) automaticTuningOption() {}
+
 // ElasticPoolSpecification represents SERVICE_OBJECTIVE = ELASTIC_POOL(name = poolname)
 type ElasticPoolSpecification struct {
 	ElasticPoolName *Identifier

parser/marshal.go

@@ -1160,6 +1160,22 @@ func databaseOptionToJSON(opt ast.DatabaseOption) jsonNode {
 			"OptionKind":  o.OptionKind,
 			"OptionState": o.OptionState,
 		}
+	case *ast.AutomaticTuningDatabaseOption:
+		node := jsonNode{
+			"$type":      "AutomaticTuningDatabaseOption",
+		}
+		if o.AutomaticTuningState != "" {
+			node["AutomaticTuningState"] = o.AutomaticTuningState
+		}
+		if len(o.Options) > 0 {
+			opts := make([]jsonNode, len(o.Options))
+			for i, subOpt := range o.Options {
+				opts[i] = automaticTuningOptionToJSON(subOpt)
+			}
+			node["Options"] = opts
+		}
+		node["OptionKind"] = o.OptionKind
+		return node
 	case *ast.DelayedDurabilityDatabaseOption:
 		return jsonNode{
 			"$type":      "DelayedDurabilityDatabaseOption",
@@ -1358,6 +1374,37 @@ func databaseOptionToJSON(opt ast.DatabaseOption) jsonNode {
 	}
 }
 
+func automaticTuningOptionToJSON(opt ast.AutomaticTuningOption) jsonNode {
+	switch o := opt.(type) {
+	case *ast.AutomaticTuningCreateIndexOption:
+		return jsonNode{
+			"$type":      "AutomaticTuningCreateIndexOption",
+			"OptionKind": o.OptionKind,
+			"Value":      o.Value,
+		}
+	case *ast.AutomaticTuningDropIndexOption:
+		return jsonNode{
+			"$type":      "AutomaticTuningDropIndexOption",
+			"OptionKind": o.OptionKind,
+			"Value":      o.Value,
+		}
+	case *ast.AutomaticTuningForceLastGoodPlanOption:
+		return jsonNode{
+			"$type":      "AutomaticTuningForceLastGoodPlanOption",
+			"OptionKind": o.OptionKind,
+			"Value":      o.Value,
+		}
+	case *ast.AutomaticTuningMaintainIndexOption:
+		return jsonNode{
+			"$type":      "AutomaticTuningMaintainIndexOption",
+			"OptionKind": o.OptionKind,
+			"Value":      o.Value,
+		}
+	default:
+		return jsonNode{"$type": "UnknownAutomaticTuningOption"}
+	}
+}
+
 func remoteDataArchiveDbSettingToJSON(setting ast.RemoteDataArchiveDbSetting) jsonNode {
 	switch s := setting.(type) {
 	case *ast.RemoteDataArchiveDbServerSetting:

parser/parse_ddl.go

@@ -2499,6 +2499,60 @@ func (p *Parser) parseAlterDatabaseSetStatement(dbName *ast.Identifier) (*ast.Al
 				OptionState: capitalizeFirst(optionValue),
 			}
 			stmt.Options = append(stmt.Options, opt)
+		case "AUTOMATIC_TUNING":
+			opt := &ast.AutomaticTuningDatabaseOption{
+				OptionKind:           "AutomaticTuning",
+				AutomaticTuningState: "NotSet",
+			}
+			// Check for = INHERIT/CUSTOM/AUTO or (sub-options)
+			if p.curTok.Type == TokenEquals {
+				p.nextToken() // consume =
+				stateVal := strings.ToUpper(p.curTok.Literal)
+				opt.AutomaticTuningState = capitalizeFirst(stateVal)
+				p.nextToken()
+			}
+			// Parse optional sub-options in parentheses
+			if p.curTok.Type == TokenLParen {
+				p.nextToken() // consume (
+				for p.curTok.Type != TokenRParen && p.curTok.Type != TokenEOF {
+					subOptName := strings.ToUpper(p.curTok.Literal)
+					p.nextToken() // consume option name
+					if p.curTok.Type == TokenEquals {
+						p.nextToken() // consume =
+					}
+					subOptValue := capitalizeFirst(strings.ToUpper(p.curTok.Literal))
+					p.nextToken() // consume value
+					switch subOptName {
+					case "CREATE_INDEX":
+						opt.Options = append(opt.Options, &ast.AutomaticTuningCreateIndexOption{
+							OptionKind: "Create_Index",
+							Value:      subOptValue,
+						})
+					case "DROP_INDEX":
+						opt.Options = append(opt.Options, &ast.AutomaticTuningDropIndexOption{
+							OptionKind: "Drop_Index",
+							Value:      subOptValue,
+						})
+					case "FORCE_LAST_GOOD_PLAN":
+						opt.Options = append(opt.Options, &ast.AutomaticTuningForceLastGoodPlanOption{
+							OptionKind: "Force_Last_Good_Plan",
+							Value:      subOptValue,
+						})
+					case "MAINTAIN_INDEX":
+						opt.Options = append(opt.Options, &ast.AutomaticTuningMaintainIndexOption{
+							OptionKind: "Maintain_Index",
+							Value:      subOptValue,
+						})
+					}
+					if p.curTok.Type == TokenComma {
+						p.nextToken()
+					}
+				}
+				if p.curTok.Type == TokenRParen {
+					p.nextToken() // consume )
+				}
+			}
+			stmt.Options = append(stmt.Options, opt)
 		case "DELAYED_DURABILITY":
 			// This option uses = with DISABLED/ALLOWED/FORCED values
 			if p.curTok.Type != TokenEquals {