Support RENAME DATABASE statement

Add parsing and explain support for RENAME DATABASE statements.

Changes:
- Add RenameDatabase field to RenameQuery AST
- Update parser to handle RENAME DATABASE syntax
- Update explain to output correct format for database renames
- Fixes 01155_rename_move_materialized_view stmt44, stmt52
- Also fixes 02096_rename_atomic_hang stmt14

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

Author: kyleconroy

ast/ast.go

@@ -981,13 +981,14 @@ type RenamePair struct {
 
 // RenameQuery represents a RENAME TABLE statement.
 type RenameQuery struct {
-	Position  token.Position `json:"-"`
-	Pairs     []*RenamePair  `json:"pairs"`             // Multiple rename pairs
-	From      string         `json:"from,omitempty"`    // Deprecated: for backward compat
-	To        string         `json:"to,omitempty"`      // Deprecated: for backward compat
-	OnCluster string         `json:"on_cluster,omitempty"`
-	Settings  []*SettingExpr `json:"settings,omitempty"`
-	IfExists  bool           `json:"if_exists,omitempty"` // IF EXISTS modifier
+	Position       token.Position `json:"-"`
+	Pairs          []*RenamePair  `json:"pairs"`                     // Multiple rename pairs
+	From           string         `json:"from,omitempty"`            // Deprecated: for backward compat
+	To             string         `json:"to,omitempty"`              // Deprecated: for backward compat
+	OnCluster      string         `json:"on_cluster,omitempty"`
+	Settings       []*SettingExpr `json:"settings,omitempty"`
+	IfExists       bool           `json:"if_exists,omitempty"`       // IF EXISTS modifier
+	RenameDatabase bool           `json:"rename_database,omitempty"` // True for RENAME DATABASE
 }
 
 func (r *RenameQuery) Pos() token.Position { return r.Position }

internal/explain/statements.go

@@ -720,6 +720,26 @@ func explainRenameQuery(sb *strings.Builder, n *ast.RenameQuery, indent string,
 		fmt.Fprintf(sb, "%s*ast.RenameQuery\n", indent)
 		return
 	}
+
+	// Handle RENAME DATABASE separately - it outputs just 2 identifiers
+	if n.RenameDatabase {
+		children := 2 // source and target database names
+		hasSettings := len(n.Settings) > 0
+		if hasSettings {
+			children++
+		}
+		fmt.Fprintf(sb, "%sRename (children %d)\n", indent, children)
+		if len(n.Pairs) > 0 {
+			// FromTable contains source database, ToTable contains target database
+			fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Pairs[0].FromTable)
+			fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Pairs[0].ToTable)
+		}
+		if hasSettings {
+			fmt.Fprintf(sb, "%s Set\n", indent)
+		}
+		return
+	}
+
 	// Count identifiers: 2 per pair if no database, 4 per pair if databases specified
 	hasSettings := len(n.Settings) > 0
 	children := 0

parser/parser.go

@@ -6922,11 +6922,14 @@ func (p *Parser) parseRename() *ast.RenameQuery {
 
 	p.nextToken() // skip RENAME
 
-	// Handle RENAME TABLE or RENAME DICTIONARY
+	// Handle RENAME TABLE, RENAME DICTIONARY, or RENAME DATABASE
 	if p.currentIs(token.TABLE) {
 		p.nextToken()
 	} else if p.currentIs(token.IDENT) && strings.ToUpper(p.current.Value) == "DICTIONARY" {
 		p.nextToken()
+	} else if p.currentIs(token.DATABASE) {
+		p.nextToken()
+		rename.RenameDatabase = true
 	} else {
 		return nil
 	}

parser/testdata/01155_rename_move_materialized_view/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt44": true,
-    "stmt52": true
-  }
-}
+{}

parser/testdata/02096_rename_atomic_hang/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt14": true
-  }
-}
+{}