Add support for ALTER TABLE DROP DETACHED PARTITION

- Add AlterDropDetachedPartition type in ast/ast.go
- Parse DROP DETACHED PARTITION syntax in parser/parser.go
- Handle new command type in explain output

Fixes 03203_drop_detached_partition_all/stmt7

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

Author: kyleconroy

ast/ast.go

@@ -680,8 +680,9 @@ const (
 	AlterMaterializeTTL     AlterCommandType = "MATERIALIZE_TTL"
 	AlterModifySetting      AlterCommandType = "MODIFY_SETTING"
 	AlterResetSetting       AlterCommandType = "RESET_SETTING"
-	AlterDropPartition      AlterCommandType = "DROP_PARTITION"
-	AlterDetachPartition    AlterCommandType = "DETACH_PARTITION"
+	AlterDropPartition         AlterCommandType = "DROP_PARTITION"
+	AlterDropDetachedPartition AlterCommandType = "DROP_DETACHED_PARTITION"
+	AlterDetachPartition       AlterCommandType = "DETACH_PARTITION"
 	AlterAttachPartition    AlterCommandType = "ATTACH_PARTITION"
 	AlterReplacePartition   AlterCommandType = "REPLACE_PARTITION"
 	AlterFetchPartition     AlterCommandType = "FETCH_PARTITION"

internal/explain/statements.go

@@ -1850,7 +1850,7 @@ func explainAlterCommand(sb *strings.Builder, cmd *ast.AlterCommand, indent stri
 		}
 	case ast.AlterModifySetting:
 		fmt.Fprintf(sb, "%s Set\n", indent)
-	case ast.AlterDropPartition, ast.AlterDetachPartition, ast.AlterAttachPartition,
+	case ast.AlterDropPartition, ast.AlterDropDetachedPartition, ast.AlterDetachPartition, ast.AlterAttachPartition,
 		ast.AlterReplacePartition, ast.AlterFetchPartition, ast.AlterMovePartition, ast.AlterFreezePartition, ast.AlterApplyPatches, ast.AlterApplyDeletedMask:
 		if cmd.Partition != nil {
 			// PARTITION ALL is shown as Partition_ID (empty) in EXPLAIN AST
@@ -2149,7 +2149,7 @@ func countAlterCommandChildren(cmd *ast.AlterCommand) int {
 		}
 	case ast.AlterModifySetting:
 		children = 1
-	case ast.AlterDropPartition, ast.AlterDetachPartition, ast.AlterAttachPartition,
+	case ast.AlterDropPartition, ast.AlterDropDetachedPartition, ast.AlterDetachPartition, ast.AlterAttachPartition,
 		ast.AlterReplacePartition, ast.AlterFetchPartition, ast.AlterMovePartition, ast.AlterFreezePartition, ast.AlterApplyPatches, ast.AlterApplyDeletedMask:
 		if cmd.Partition != nil {
 			children++

parser/parser.go

@@ -5475,6 +5475,14 @@ func (p *Parser) parseAlterCommand() *ast.AlterCommand {
 				cmd.ConstraintName = p.current.Value
 				p.nextToken()
 			}
+		} else if p.currentIs(token.IDENT) && strings.ToUpper(p.current.Value) == "DETACHED" {
+			// DROP DETACHED PARTITION
+			p.nextToken() // skip DETACHED
+			if p.currentIs(token.PARTITION) {
+				p.nextToken() // skip PARTITION
+				cmd.Type = ast.AlterDropDetachedPartition
+				cmd.Partition = p.parseExpression(LOWEST)
+			}
 		} else if p.currentIs(token.PARTITION) {
 			cmd.Type = ast.AlterDropPartition
 			p.nextToken()

parser/testdata/03203_drop_detached_partition_all/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt7": true
-  }
-}
+{}