Add SYSTEM RELOAD DICTIONARY and DELETE FROM support

- SYSTEM RELOAD DICTIONARY now outputs dictionary name twice as expected
- Add DeleteQuery AST type and parsing for DELETE FROM ... WHERE
- Add explain output for DeleteQuery

Author: claude

ast/ast.go

@@ -672,6 +672,18 @@ func (t *TruncateQuery) Pos() token.Position { return t.Position }
 func (t *TruncateQuery) End() token.Position { return t.Position }
 func (t *TruncateQuery) statementNode()      {}
 
+// DeleteQuery represents a lightweight DELETE statement.
+type DeleteQuery struct {
+	Position token.Position `json:"-"`
+	Database string         `json:"database,omitempty"`
+	Table    string         `json:"table"`
+	Where    Expression     `json:"where,omitempty"`
+}
+
+func (d *DeleteQuery) Pos() token.Position { return d.Position }
+func (d *DeleteQuery) End() token.Position { return d.Position }
+func (d *DeleteQuery) statementNode()      {}
+
 // UseQuery represents a USE statement.
 type UseQuery struct {
 	Position token.Position `json:"-"`

internal/explain/explain.go

@@ -238,6 +238,8 @@ func Node(sb *strings.Builder, node interface{}, depth int) {
 		explainOptimizeQuery(sb, n, indent, depth)
 	case *ast.TruncateQuery:
 		explainTruncateQuery(sb, n, indent)
+	case *ast.DeleteQuery:
+		explainDeleteQuery(sb, n, indent, depth)
 	case *ast.CheckQuery:
 		explainCheckQuery(sb, n, indent)
 	case *ast.CreateIndexQuery:

internal/explain/statements.go

@@ -1518,6 +1518,25 @@ func explainTruncateQuery(sb *strings.Builder, n *ast.TruncateQuery, indent stri
 	}
 }
 
+func explainDeleteQuery(sb *strings.Builder, n *ast.DeleteQuery, indent string, depth int) {
+	if n == nil {
+		fmt.Fprintf(sb, "%s*ast.DeleteQuery\n", indent)
+		return
+	}
+
+	// Count children: Where expression + table identifier
+	children := 1 // table identifier
+	if n.Where != nil {
+		children++
+	}
+
+	fmt.Fprintf(sb, "%sDeleteQuery  %s (children %d)\n", indent, n.Table, children)
+	if n.Where != nil {
+		Node(sb, n.Where, depth+1)
+	}
+	fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Table)
+}
+
 func explainCheckQuery(sb *strings.Builder, n *ast.CheckQuery, indent string) {
 	if n == nil {
 		fmt.Fprintf(sb, "%s*ast.CheckQuery\n", indent)

parser/parser.go

@@ -205,6 +205,8 @@ func (p *Parser) parseStatement() ast.Statement {
 		return p.parseSet()
 	case token.UPDATE:
 		return p.parseUpdate()
+	case token.DELETE:
+		return p.parseDelete()
 	case token.OPTIMIZE:
 		return p.parseOptimize()
 	case token.SYSTEM:
@@ -4968,6 +4970,39 @@ func (p *Parser) parseUpdate() *ast.UpdateQuery {
 	return update
 }
 
+func (p *Parser) parseDelete() *ast.DeleteQuery {
+	del := &ast.DeleteQuery{
+		Position: p.current.Pos,
+	}
+
+	p.nextToken() // skip DELETE
+
+	// Skip optional FROM
+	if p.currentIs(token.FROM) {
+		p.nextToken()
+	}
+
+	// Parse table name (can be database.table)
+	tableName := p.parseIdentifierName()
+	if tableName != "" {
+		if p.currentIs(token.DOT) {
+			p.nextToken()
+			del.Database = tableName
+			del.Table = p.parseIdentifierName()
+		} else {
+			del.Table = tableName
+		}
+	}
+
+	// Parse WHERE clause
+	if p.currentIs(token.WHERE) {
+		p.nextToken() // skip WHERE
+		del.Where = p.parseExpression(LOWEST)
+	}
+
+	return del
+}
+
 func (p *Parser) parseUse() *ast.UseQuery {
 	use := &ast.UseQuery{
 		Position: p.current.Pos,
@@ -5483,7 +5518,14 @@ func (p *Parser) parseSystem() *ast.SystemQuery {
 				p.nextToken()
 			}
 		} else {
-			sys.Table = tableName
+			// For RELOAD DICTIONARY commands, the dictionary name appears as both database and table in EXPLAIN
+			if strings.Contains(strings.ToUpper(sys.Command), "RELOAD DICTIONARY") ||
+				strings.Contains(strings.ToUpper(sys.Command), "DROP REPLICA") {
+				sys.Database = tableName
+				sys.Table = tableName
+			} else {
+				sys.Table = tableName
+			}
 		}
 	}
 

parser/testdata/01036_no_superfluous_dict_reload_on_create_database/metadata.json

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

parser/testdata/01225_drop_dictionary_as_table/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true
-  }
-}
+{}

parser/testdata/01254_dict_create_without_db/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt4": true
-  }
-}
+{}

parser/testdata/01254_dict_load_after_detach_attach/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt6": true
-  }
-}
+{}

parser/testdata/02291_dictionary_scalar_subquery_reload/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt10": true
-  }
-}
+{}

parser/testdata/02319_lightweight_delete_on_merge_tree/metadata.json

@@ -1,14 +1,5 @@
 {
   "explain_todo": {
-    "stmt11": true,
-    "stmt16": true,
-    "stmt26": true,
-    "stmt30": true,
-    "stmt45": true,
-    "stmt52": true,
-    "stmt6": true,
-    "stmt67": true,
-    "stmt72": true,
-    "stmt74": true
+    "stmt45": true
   }
 }